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Journal articleAlimard P, Li L, Cazaly S, et al., 2026,
A scalable route to mixed and layered sandwich-structured carbonaceous–anatase TiO2 coatings with bi-functional photocatalytic activity for air pollution remediation and solar water splitting
, Carbon, Vol: 246, ISSN: 0008-6223This study showcases how carbonaceous materials, including graphene (G), fullerene (F), and multi-walled carbon nanotubes (MWCNTs), can be integrated within titanium dioxide (TiO2) films as either: (i) mixed or (ii) layered sandwich structures (TiO2/carbonaceous material/TiO2) and show bifunctional photocatalytic activity. Our composites are engineered to address both NOx pollution and water splitting within the same platform. In the mixed composite (TGmix), graphene's high conductivity and electron-accepting ability enhance the photo-oxidation of NOx, where under UVA light 17.6 % NO and 9.6 % total NOx removal was seen, which was significantly higher than TiO2 alone, which showed 6.8 % NO and 1.3 % total NOx removal. Whereas in the sandwich-layered composite (TGT), the architecture promotes hole accumulation on the surface, favouring water splitting, with incident-photon-to-current efficiency (IPCE) reaching 68 % at 1.23 VRHE (pH = 7) under 250 nm illumination; a factor of ∼2 increase compared to TiO2 alone. Transient photocurrent (TPC) and diffuse reflectance transient absorption spectroscopy (DR-TAS) were employed operando to probe the kinetics of electron extraction and hole-mediated water oxidation. At 1.23 VRHE, the TGT sample showed slightly faster electron extract kinetics to T (TGT: t50 %–0.25 ms and T: t50 %–0.268 ms), along with a significantly higher long-lived hole carrier population that drove water oxidation, which were found to linearly correlate with the observed photocurrent density.Our wholistic study, including in operando investigations, informs the rational design of active carbonaceous composite coatings within anatase TiO2 that can be grown at scale for applications in NOx air pollution remediation and solar water splitting.
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Journal articleXie J, Tam B, Cai Y, et al., 2025,
Plasmonic Pd nanoparticles at the electrode-semiconductor interface enhance the activity of bismuth vanadate for solar-driven glycerol oxidation
, Inorganic Chemistry Frontiers, ISSN: 2052-1545This study demonstrates that the integration of plasmonic palladium (Pd) nanoparticles between a bismuth vanadate (BVO) coating and an electrode interface can significantly improve solar-driven glycerol oxidation. Pd nanoparticles of controllable shape, size and coverage were produced using a novel aerosol-assisted chemical vapour deposition (AACVD) synthetic route and then coated with BVO using the same technique. The nanoparticles enhanced visible light absorption and crystallinity. At 1.23 VRHE, the photocurrent density of bare BVO increased from 0.62 mA cm−2 in the absence of glycerol to 1.20 mA cm−2 with 0.5 M glycerol. When Pd nanoparticles were incorporated beneath BVO, the photocurrent further increased from 0.86 mA cm−2 without glycerol to 1.58 mA cm−2 with 0.5 M glycerol, and the incident photon-to-current conversion efficiency (IPCE) boosted from ∼15% to ∼40% at 400 nm. Ultra-fast transient absorption spectroscopy suggests that the addition of Pd nanoparticles introduces additional charge transfer pathways, including hot electron injection and plasmon-coupled states, which prolong carrier lifetimes and suppress recombination. These combined effects provide a promising strategy to improve the efficiency and durability of photoelectrochemical devices for sustainable fuel generation and selective organic oxidation reactions.
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Journal articleWaehayee A, Ngamwongwan L, Kafizas A, et al., 2025,
Enhanced photocatalytic efficiency of Bi2MoO6 for water and p-nitroaniline reduction via iodate (I5+) substitution: Implications of small polaron formation
, Chemical Engineering Journal, Vol: 519, ISSN: 1385-8947The wide range of potential applications for photocatalysis has made research on photocatalytic materials highly active. However, various limitations hinder large-scale applications of photocatalysis, making the search for novel and improved catalysts an ongoing pursuit. To achieve this, a detailed analysis of material characteristics and charge transfer behavior is crucial. This study investigates the enhancement of Bi2MoO6 (BMO) photocatalytic performance through iodate (I5+) substitution, focusing on its impact on charge transport and reaction efficiency. Employing experimental and computational methods, we propose that carrier migration in Bi2MoO6 follow a small polaron model. Substituting I5+ into Bi2MoO6 increase the exposure on {100} facets, where polaron hopping along the facet is easier than on the exposed {010} facet of pristine Bi2MoO6. Moreover, this substitution creates defects and increases charge carrier concentration by approximately threefold. The increased Fermi energy level enables I-doped Bi2MoO6 to generate H2 and enhance p-nitroaniline reduction activity. As a result, the catalyst exhibits nearly 10 times higher efficiency in both reactions. This work highlights a defect-engineering strategy that potentially involves polaronic transport to improve photocatalyst design, offering a promising solution for sustainable energy applications, including water splitting and selective organic transformations.
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Journal articleHwang GB, Heo KJ, Jee W, et al., 2025,
Optimizing the Au particle doping size for enhanced photocatalytic disinfection under low-intensity visible light
, ACS Nano, Vol: 19, Pages: 27740-27753, ISSN: 1936-0851Here, we present the effect of 1.2–9.9 nm Au particles on crystal violet-treated polymer under a low intensity of visible light. The use of Au particles ≤ 6.3 nm promoted charge carrier transfer from crystal violet to Au particles. Photospectroscopy analyses and DFT computations revealed that a change in the electronic band structure caused by the size reduction of the particle altered the charge carrier transfer pathway in crystal violet. Especially for crystal violet─1.2 nm Au particles, charge carrier transfer predominantly occurs at the S1 of crystal violet because the T1 state lacks sufficient potential energy for transfer. 1.2 nm Au particles on crystal violet not only most significantly enhanced the generation of O2•–, H2O2, and •OH by minimizing unnecessary side reactions or energy loss but also showed the most potent disinfection activity against Staphylococcus aureus, even at low visible light flux levels (0.037–0.054 mW cm–2), which resulted in a 5.3 log reduction in viable bacteria after 6 h exposure to visible light. This finding provides fundamental insights into the Au effect as a cocatalyst in photocatalysts and the development of light-activated self-sterilizing surfaces that can be applied to various hospital surfaces to prevent the spread of pathogens, which remains a global challenge.
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Journal articleAlimard P, Cazaly S, Itskou I, et al., 2025,
Exploring the influence of carbonaceous material on the photocatalytic performance of the composites containing Bi–BiOBr and P25 TiO2 for NOx remediation
, ChemPhysChem, Vol: 26, ISSN: 1439-4235The Bi–BiOBr–P25 TiO2 composite material exhibits high and synergistic improvements in the photocatalytic activity for nitrogen oxides (NOx = NO + NO2) removal. Herein, the influence of adding carbonaceous material to this composite, namely graphene (G), graphene oxide (GO), carbon nanotubes (CNT), and buckminsterfullerene (F) is explored; all at 1 wt%. Samples are synthesised using a one-pot solvothermal method. The structural and morphological properties, composition, and photocatalytic performance of all samples are examined using scanning electron microscopy, carbon–hydrogen–nitrogen elemental analysis, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, attenuated total reflectance–Fourier transform infrared spectroscopy, ultraviolet–visible (UV–vis) spectroscopy, X-ray photoelectron spectroscopy, N2 sorption at 77 K, photoluminescence spectroscopy, diffuse reflectance transient absorption spectroscopy), and photocatalytic testing against NOx gas in accordance with ISO protocol (22197-1:2016). Among the studied carbonaceous composites, the composite including GO shows the highest performance toward NOx remediation. For reactions in NO gas, it shows a combined higher NOx removal rate (21.9%) than its parent materials P25 (8.7%), Bi–BiOBr (6.5%), and GO (0%). For reactions in NO2 gas, it shows a higher NOx removal rate (≈15%) than its parent materials P25 (≈10%), Bi–BiOBr (≈5%), and GO (0%).
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Journal articleCreasey GH, Kafizas A, Hankin A, 2025,
Investigating the beneficial effects of a WO3 seed layer on the mechanical and photoelectrochemical stability of WO3|BiVO4|NiFeOOH photoanodes under operational conditions
, MRS Communications, Vol: 15, Pages: 721-730, ISSN: 2159-6859Scalable and durable photoelectrodes are essential for technological breakthroughs in photoelectrochemical systems, yet the fragility of nanostructured photocatalyst materials in industrially relevant operating conditions is rarely explored. Herein, we advance understanding of the importance of morphology and temperature on stability and performance of nanostructured WO3|BiVO4|NiFeOOH photoanodes. The integration of a planar WO3 seed layer beneath nanostructured WO3, improved mechanical stability at 40°C with flowing electrolyte approximately twofold compared with materials where a seed layer was not integrated. This work provides a pathway through which robust photoelectrode systems can be engineered to enable the advancement of up-scaled photoelectrochemical water splitting.
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Journal articleItskou I, Sageer SC, Dawson DM, et al., 2025,
Boron-functionalized graphitic carbon nitride materials for photocatalytic applications: effects on chemical, adsorptive, optoelectronic, and photocatalytic properties
, ACS Materials Au, Vol: 5, Pages: 656-674, ISSN: 2694-2461Graphitic carbon nitride (gC3N4, or CN herein) is widely studied as a photocatalyst owing to its ease of synthesis, high stability, and optoelectronic properties. However, its photocatalytic performance often remains limited, and a common approach to tune its function and enhance its performance is by doping. Boron (B) functionalization of CN has showed a potential benefit on photocatalytic performance for several reactions. However, the reason for this improvement and the links between synthesis method, exact B chemical environment, and performance remain unclear. Here, we present a fundamental study that elucidates the influence of (i) B functionalization, (ii) B content, and (iii) choice of B precursor on the physicochemical, adsorptive, optoelectronic, and photocatalytic properties of bulk B-CN. We synthesized two sets of B-CN materials (0.5–11 at% B), using either elemental boron or boric acid as precursors. The samples were characterized using several imaging and spectroscopic techniques, which confirm the integration of B into the material through B–O bonding and the creation of B clusters in the case of the boron precursor, with density functional theory (DFT) calculations supporting our analyses. The distribution of B atoms within B-CN particles remained heterogeneous. Compared to CN, B-functionalized materials show enhanced porosity and CO2 uptake, with similar degrees of light absorption and deeper energy band positions. Transient absorption spectroscopy (TAS) measurements showed that charge carrier populations, lifetimes, and kinetics were not significantly affected by B functionalization; however, at 5 at% B doping, an increase in the concentration of charge carriers was seen. Higher B content enhances the photocatalytic NOx removal under UVA irradiation (almost two-fold) and the selectivity to NO3– from NOx photooxidation, but has no significant effect on CO2 photoreduction, compared to pristine CN. Overall, this study provides fundam
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Journal articleSachs M, Harnett-Caulfield L, Davies B, et al., 2025,
Metal-centred states control carrier lifetimes in transition metal oxide photocatalysts
, Nature Chemistry, ISSN: 1755-4330Efficient sunlight-to-energy conversion requires materials that can generate long-lived charge carriers upon illumination. However, the targeted design of semiconductors possessing intrinsically long lifetimes remains a key challenge. Here using a series of transition metal oxides, we establish a link between carrier lifetime and electronic configuration in transition metal-based semiconductors. We identify a subpicosecond relaxation mechanism via metal-centred ligand field states that compromise quantum yields in open d-shell transition metal oxides (for example, Fe2O3, Co3O4, Cr2O3 and NiO), which is more reminiscent of molecular complexes than crystalline semiconductors. We found that materials with spin-forbidden ligand field transitions could partially mitigate this relaxation pathway, explaining why Fe2O3 achieves higher photoelectrochemical activity than other visible light-absorbing transition metal oxides. However, achieving high yields of long-lived charges requires transition metal oxides with d0 or d10 electronic configurations (for example, TiO2 and BiVO4), where ligand field states are absent. These trends translate to transition metal-containing semiconductors beyond oxides, enabling the design of photoabsorbers with better-controlled recombination channels in photovoltaics, photocatalysis and communication devices.
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Journal articleOlaifa O, Alimard P, Itskou I, et al., 2025,
Purifying the air with photocatalysis: developing bismuth oxybromide/ copper phthalocyanine composite photocatalyst filters with enhanced activity for NOx removal
, ChemPhotoChem, Vol: 9, ISSN: 2367-0932The utilization of photocatalysis is a promising new strategy for reducing the substantially high levels of nitrogen oxides (NO<jats:sub>x</jats:sub>) pollution in cities. In this work, we examine bismuth oxybromide (BiOBr) as a viable substitute due to its narrower band gap and high stability. Powders were synthesised using co‐precipitation, solvothermal and hydrothermal synthesis methods, resulting in particles with various morphologies including microcubes, microspheres, microflowers, clusters and microsquares. Their photocatalytic activities being evaluated in accordance with ISO 22197–1 : 2016 protocol under UV and visible light. The samples exhibiting the highest performance were produced by co‐precipitation, showing ~7 % NO and ~2 % NO<jats:sub>x</jats:sub> removal under visible light and ~19 % NO and ~10 % NO<jats:sub>x</jats:sub> removal under UV light. The activity was further enhanced, by incorporating copper(II) phthalocyanine (CuPc) through an impregnation method, where the optimal loading of 0.01 mol% surpassed the activity of the benchmark photocatalyst TiO<jats:sub>2</jats:sub> P25, with ~22 % NO and ~9 % NO<jats:sub>x</jats:sub> removal under visible light and ~40 % NO and ~23 % NO<jats:sub>x</jats:sub> under UV light. We anticipate that these BiOBr/CuPc photocatalyst filters can be applied within air purification systems and powered using less energy intensive visible light sources to remedy air pollution.
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Journal articleJiamprasertboon A, Kafizas A, Eknapakul T, et al., 2025,
Insights into unlocking the latent photocatalytic H2 production activity in the protonated Aurivillius-phase layered perovskite Na0.5Bi2.5Nb2O9
, Materials Research Bulletin, Vol: 186, ISSN: 0025-5408The introduction of protonated interlayers in layered perovskite compounds has already demonstrated promising results in terms of photocatalytic activity. However, the mechanisms behind the observed enhancements remain unexplored. Here, we report a rapid and efficient proton exchange process for Na0.5Bi2.5Nb2O9 (ABNO), involving selective leaching of (Bi2O2)2- layers accompanied by the introduction of interlayer H+. This process, using acid treatment at room temperature is completed within only 24 h, the fastest method to date for a layered perovskite. Protonation induces changes at the molecular and electronic level, investigated using Synchrotron-based techniques, diffused reflectance spectroscopy (DRS), DFT calculation, and transient absorption spectroscopy (TAS), influencing the electronic band structure, surface properties, and charge carrier dynamics of the compounds. After protonation, BET surface area increases by > 20 times, to 156.19 m2/g. These structural and surface modifications unlock the material's latent photocatalytic potential, enabling H+ exchanged Na0.5Bi2.5Nb2O9 (HABNO) to achieve a H2 production rate of 242 μmol/h/g. This work delves into the photocatalytic mechanism, revealing how substitution by H+ provides more active sites and enhances the ability of the material to generate more highly reactive electrons that can participate in H2O reduction. This study highlights the promising strategy of altering the structure and electronic properties of layered materials through protonation to improve their performance for applications in photocatalysis for a cleaner and more sustainable future.
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Journal articleTam B, Pike SD, Nelson J, et al., 2025,
The scalable growth of high-performance nanostructured heterojunction photoanodes for applications in tandem photoelectrochemical-photovoltaic solar water splitting devices
, Chemical Science, Vol: 16, Pages: 7794-7810, ISSN: 2041-6520Due to their complementary absorption characteristics and band energy structure, the BiVO4-coated WO3 heterojunction architecture is commonly employed as a metal oxide photoanode for the water oxidation half-reaction. The energy level ordering results in a staggered heterojunction that can effectively separate photoexcited electrons into the WO3 layer towards the current collector and photoexcited holes into the BiVO4 layer towards the interface with the electrolyte. Chemical vapour deposition (CVD) is an upscalable technique for fabricating large-area thin films of a wide range of semiconductors with nanoscale control. The fluorine-doped tin oxide (FTO)-coated transparent conductive glass substrates used herein are mass-produced by the glass industry with atmospheric pressure CVD and so the entire photoelectrode could be produced in one production process on float glass panels. This work is a detailed study of the use of atmospheric pressure CVD to fully-fabricate high-performance BiVO4-coated WO3 nanostructures (500–2000 nm in length with 25–100 nm thick BiVO4 coatings) for photoelectrochemical (PEC) water splitting. Incident photon-to-current efficiency measurements were used to calculate optimal solar predicted photocurrents of 1.92 and 2.61 mA cm−2 (2.3% and 3.2% solar-to-hydrogen efficiency if coupled to a hypothetical photovoltaic providing 1.23 V) for WO3/BiVO4 heterojunction samples under front and back-illumination, respectively. The heterojunction showed more than additive improvements over the parent materials, with bare WO3 and BiVO4 samples showing 0.68 and 0.27 mA cm−2 and 0.50 and 0.87 mA cm−2 under front and back-illumination, respectively. Simulations of the current–voltage characteristics of tandem crystalline silicon photovoltaic modules coupled to the PEC devices were consistent with the solar predicted photocurrents. These promising results for BiVO4-coated WO3 nanoneedles fully-deposited by atmospheric press
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Journal articleCreasey GH, McCallum TW, Ai G, et al., 2025,
Mechanically and photoelectrochemically stable WO₃|BiVO₄|NiFeOOH photoanodes synthesised by a scalable chemical vapour deposition method
, Journal of Materials Chemistry A, Vol: 13, Pages: 11585-11604, ISSN: 2050-7488The development of scalable, stable and high performance photoelectrodes remains the major bottleneck in up-scaling photoelectrochemical (PEC) water splitting systems. A photoanode structure of particular promise is WO3|BiVO4, where the formation of staggered heterojunction between nanostructured WO3 and a thin layer of BiVO4 mitigates charge carrier mobility limitations present for BiVO4 alone and suppresses recombination. Although these electrodes remain prone to photo-corrosion, this effect can be mitigated through the application of water oxidation surface co-catalysts. An additional challenge that has rarely been addressed in the literature to date is the need for strong adhesion to the substrate and mechanical stability of these photoelectrodes, so that they can withstand flow-induced shear stress exerted by the electrolyte in continuous flow under operational conditions. Herein, we propose a scalable route to synthesising WO3|BiVO4|NiFeOOH photoanodes entirely by aerosol-assisted chemical vapour deposition (AA-CVD). The mechanical stability of the WO3|BiVO4 heterojunction was optimised by tuning the morphology of the WO3 underlayer and improving its adhesion to the FTO transparent substrate. To address BiVO4 dissolution at the electrode|electrolyte interface, we fabricated a NiFeOOH co-catalyst by a novel AA-CVD method. This suppressed BiVO4 dissolution and enhanced the water oxidation performance of the photoanode, characterised by linear sweep voltammetry (LSV), photoelectrochemical impedance spectroscopy (PEIS) and chopped chronoamperometry. The photoanode materials were physically characterised by X-ray diffraction (XRD), UV-Vis spectroscopy, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Our optimised photoanodes with 1 cm2 photoactive area delivered a stable photocurrent density of 1.75
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Journal articleJiamprasertboon A, Promkamat P, Kafizas A, et al., 2025,
Porous nanosheets and excellent charge carrier dynamics in Ag+-Doped Na0.5Bi2.5Nb2O9 aurivillius-phase layered perovskite for enhanced visible-light photocatalytic activity
, Chemistry: An Asian Journal, ISSN: 1861-471XThe new Aurivillius layered perovskite compounds, AgxNa0.5-xBi2.5Nb2O9 (AGBNO), were successfully synthesized using a hydrothermal technique followed by conventional, microwave-assisted, and acid-assisted ion exchange procedures. The formation of these compounds was evidenced by several techniques. A single-phase crystal structure was identified by XRD patterns, and expanded lattice parameters were revealed by crystal structure refinement. Chemical composition was verified by EDS, XPS, and ICP-OES analyses. Bandgap energies remained similar to the parent Na0.5Bi2.5Nb2O9 host material. Ag+ incorporation significantly enhanced photocatalytic performance for Rhodamine B degradation under visible light, which was attributed to the intrinsic catalytic properties of Ag+ as a noble metal cation. The variations in photocatalytic activities among the series of Ag+-doped samples produced were associated with differences in morphology, specific surface area, and charge carrier dynamics. The AGBNO sample prepared via acid-assisted ion exchange exhibited the highest photocatalytic efficiency, which was attributed to its highly porous nanosheet morphology, largest surface area, and excellent charge carrier dynamics, including high initial charge carrier concentration, optimal lifetime, high charge mobility, efficient charge separation, and transfer. Overall, this study demonstrates the potential of designing Aurivillius-phase layered perovskite photocatalysts with enhanced activity for wastewater remediation and environmental applications through noble metal cation doping.
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Book chapterKafizas A, 2025,
The Application of TiO2 for the Photocatalytic Conversion of the Nitrogen Oxides - NO and NO2
, Nanostructured Tio Synthesis Photocatalytic Properties and Applications, Pages: 361-388Nitric oxide (NO) and nitrogen dioxide (NO<inf>2</inf>) gases are together referred to as NO<inf>x</inf>, which are highly toxic to humans when inhaled. Today, NO<inf>x</inf> gas is predominantly formed by human activities, such as combustion processes. Once dispersed, NO<inf>x</inf> emissions are challenging to remedy, as concentrations in the atmosphere are typically lower than a part per million. Nevertheless, TiO<inf>2</inf>-based photocatalysts can treat dilute levels of NO<inf>x</inf>, functioning passively using ambient light. In this chapter, we present recent developments in the use of TiO<inf>2</inf> -based photocatalysts for remediating NO<inf>x</inf>, covering field trials of products that have been developed for various commercial applications, the rational design of more active catalysts, and future challenges and perspectives.
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Journal articleHeiba HF, Bullen JC, Kafizas A, et al., 2024,
Engineered Sn-TiO2@SnO2 and SnO2@Sn-TiO2 heterophotocatalysts for enhanced As(III) remediation: a comprehensive bulk and surface characterization and precise photocatalytic oxidation rates determination
, Colloids and Surfaces A: Physicochemical and Engineering Aspects, Vol: 702, ISSN: 0927-7757Arsenite, As(III), is a highly toxic form of arsenic that poses a significant risk to human health if present in drinking water. Oxidation of As(III) to the less toxic As(V) using TiO2 as photocatalyst is an attractive solution in water treatment applications but challenged the high bandgap energy. In this study, we investigate the potential of doping TiO2 with Sn to reduce the bandgap and hence to improve the photocatalytic oxidation (PCO). To this end, we studied first the effect of varying Sn:TiO2 molar doping on the structure of the newly synthesized SnO2@TiO2 and Sn-TiO2@SnO2 hetero photocatalysts. We found that at low Sn:TiO2 doping ratios (0.1Sn:1TiO2), SnO2 tends to float on the surface and form a coat around the TiO2 (SnO2@Sn-TiO2), whereas at higher doping ratio (1Sn:1TiO2) a Sn-TiO2 coat forms alongside SnO2 clusters in the core of the catalyst (Sn-TiO2@SnO2). We assessed the PCO and observed significant shifts to lower conduction and valence band edge energies and a reduction of the bandgap at higher doping ratios. The smallest bandgap was 2.87 eV with a doping ratio of 1Sn:1TiO2. Sn-TiO2@SnO2 and as SnO2@Sn-TiO2 improved the PCO of TiO2 by ∼30 and 46 %, respectively. We finally determined the rate constant (k) for the As(III) oxidation using a combination of spectrochemical and surface sensitive techniques and determined for a 1Sn:1TiO2 (i.e. Sn-TiO2@SnO2) catalyst a value of 0.055 ±0.002 min−1, i.e., 78 folds faster than using only TiO2. We conclude that Sn doping of TiO2 is a very promising approach for improving the PCO of As(III) in water treatment.
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Journal articleHeiba HF, Bullen JC, Kafizas A, et al., 2024,
Role of the Sn-TiO<sub>2</sub>/Ti-SnO<sub>2</sub> Heterojunction in Enhancing the Photocatalytic Oxidation of Arsenite (As<SUP>III</SUP>) through the Promotion of Charge Carrier Lifetime
, ACS APPLIED MATERIALS & INTERFACES, Vol: 16, Pages: 69239-69252, ISSN: 1944-8244 -
Journal articleDutta A, Porat H, Goldreich A, et al., 2024,
Laser exfoliated 2D MXene for supercapacitor applications
, Chemical Engineering Journal, Vol: 500, ISSN: 1385-8947MXenes-based compounds, particularly Ti3C2Tx, have been studied intensively as electrodes for supercapacitors due to their layered structure and high conductivity, enabling facile ion diffusion and charge transfer. However, tight restacking of the 2D layers in these materials limits their practical, accessible surface area, thereby impeding their capacity and rate capability performance. To mitigate this phenomenon, we present a new approach using a processing method based on laser beam irradiation to modify Ti3C2Tx films. We found that the laser treatment induces chemical and morphological changes, ultimately optimizing the stacking arrangement of the MXene electrodes and consequently enhancing their capacity in both neutral and acidic electrolytes. Furthermore, the laser-modified MXene electrodes demonstrate excellent rate capabilities, showing 84 % retention at extreme rates of 0.5 V compared to only 33 % of the original Ti3C2Tx electrodes. Finally, we discuss the chemical and physical changes induced by the laser treatments and their influence on the electrochemical behavior of the lasered MXene. The principles of laser exfoliation discovered in this study can be implemented in broader 2D materials for various applications.
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Journal articleAlimard P, Gong C, Itskou I, et al., 2024,
Achieving high photocatalytic NOx removal activity using a Bi/BiOBr/TiO2 composite photocatalyst
, Chemosphere, Vol: 368, ISSN: 0045-6535Fossil fuel combustion generates nitrogen oxides (NO + NO2 = NOx), which pose threats to the environment and human health. Although commercial products containing titanium dioxide (TiO2) can remedy NOx pollution by photocatalysis, they only function in the ultraviolet (UV). On the other hand, bismuth oxybromide (BiOBr) is active in the visible. BiOBr is stable, affordable, and non-toxic, making it an appealing alternative. In addition, nanoparticulate Bi metal can further enhance visible light absorption through its surface plasmon properties and charge carrier lifetime by spatially separating charge. In this study, to enhance the visible-light activity of TiO2-based photocatalysts for NOx pollution, a composite of Bi-decorated BiOBr/TiO2 was synthesised using a solvothermal method across varying the Ti/Bi atomic ratio (0.2, 2.2, 4.4, and 6.6), and synthesis duration (6h, 12h, and 18h). The photocatalytic performance of the synthesised composites for NO gas removal was investigated using an adapted ISO method (22197–1:2016). Analysis showed that the preferential growth of the (010) crystal facet in BiOBr and the presence of Bi metal both play an important role in the superior photocatalytic activity seen in our Bi-decorated BiOBr/TiO2 composite. The composites were characterised using X-ray diffraction (XRD), attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR), high-resolution scanning electron microscopy (HR-SEM), UV–Vis diffuse reflectance (DRS) spectroscopy, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Brunauer-Emmett-Teller (BET) analysis, thermogravimetric analysis (TGA), and diffuse reflectance transient absorption spectroscopy (DR-TAS). Our research shows that the Bi/BiOBr–TiO2 composite synthesised through a 12h solvothermal meth
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Journal articleZhao S, Jia C, Shen X, et al., 2024,
The aerosol-assisted chemical vapour deposition of Mo-doped BiVO4 photoanodes for solar water splitting: an experimental and computational study
, Journal of Materials Chemistry A, Vol: 12, Pages: 26645-26666, ISSN: 2050-7488BiVO4 is one of the most promising light absorbing materials for use in photoelectrochemical (PEC) water splitting devices. Although intrinsic BiVO4 suffers from poor charge carrier mobility, this can be overcome by Mo-doping. However, for Mo-doped BiVO4 to be applied in commercial PEC water splitting devices, scalable routes to high performance materials need to be developed. Herein, we propose a scalable aerosol-assisted chemical vapour deposition (AA-CVD) route to high performance Mo-doped BiVO4. The materials were characterised using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible absorption spectroscopy, and a range of PEC tests. By studying a range of Mo-precursor doping levels (0 to 12% Mo : V), an optimum precursor doping level was found (6% Mo : V); substituting V5+ sites in the host structure as Mo6+. In PEC water oxidation the highest performing material showed an onset of photocurrent (Jon) at ∼0.6 VRHE and a theoretical solar photocurrent (TSP) of ∼1.79 mA cm−2 at 1.23 VRHE and 1 sun irradiance. Importantly, Mo-doping was found to induce a phase change from monoclinic clinobisvanite (m-BiVO4), found in undoped BiVO4, to tetragonal scheelite (t-BiVO4). The effect of Mo-doping on the phase stability, structural and electronic properties was examined with all-electron hybrid exchange density functional theory (DFT) calculations. Doping into V and Bi sites at 6.25 and 12.5 at% was calculated for t-BiVO4 and m-BiVO4 phases. In accord with our observations, 6.25 at% Mo doping into the V sites in t-BiVO4 is found to be energetically favoured over doping into m-BiVO4 (by 2.33 meV per Mo atom inserted). The computed charge density is consistent with n-doping of the lattice as Mo6+ replaces V5+ generating an occupied mid-gap state ∼0.4 eV below the conduction band minimum (CBM) which is primarily of Mo-4d character. Doubling this do
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Journal articleItskou I, Kafizas A, Nevjestic I, et al., 2024,
Effects of phosphorus doping on amorphous boron nitride’s chemical, sorptive, optoelectronic, and photocatalytic properties
, The Journal of Physical Chemistry C, Vol: 128, Pages: 13249-13263, ISSN: 1932-7447Amorphous porous boron nitride (BN) represents a versatile material platform with potential applications in adsorptive molecular separations and gas storage, as well as heterogeneous and photo-catalysis. Chemical doping can help tailor BN’s sorptive, optoelectronic, and catalytic properties, eventually boosting its application performance. Phosphorus (P) represents an attractive dopant for amorphous BN as its electronic structure would allow the element to be incorporated into BN’s structure, thereby impacting its adsorptive, optoelectronic, and catalytic activity properties, as a few studies suggest. Yet, a fundamental understanding is missing around the chemical environment(s) of P in P-doped BN, the effect of P-doping on the material features, and how doping varies with the synthesis route. Such a knowledge gap impedes the rational design of P-doped porous BN. Herein, we detail a strategy for the successful doping of P in BN (P-BN) using two different sources: phosphoric acid and an ionic liquid. We characterized the samples using analytical and spectroscopic tools and tested them for CO2 adsorption and photoreduction. Overall, we show that P forms P–N bonds in BN akin to those in phosphazene. P-doping introduces further chemical/structural defects in BN’s structure, and hence more/more populated midgap states. The selection of P source affects the chemical, adsorptive, and optoelectronic properties, with phosphoric acid being the best option as it reacts more easily with the other precursors and does not contain C, hence leading to fewer reactions and C impurities. P-doping increases the ultramicropore volume and therefore CO2 uptake. It significantly shifts the optical absorption of BN into the visible and increases the charge carrier lifetimes. However, to ensure that these charges remain reactive toward CO2 photoreduction, additional materials modification strategies should be explored in future work. These strategies could include the
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Dr. Andreas Kafizas
Leader - Solar Coatings Group
e-mail: a.kafizas@imperial.ac.uk
tel: +44(0)20 7594 6752
twitter: @CoatingsSolar