Publications
95 results found
Temerov F, Baghdadi Y, Rattner E, et al., 2022, A Review on Halide Perovskite-Based Photocatalysts: Key Factors and Challenges, ACS APPLIED ENERGY MATERIALS, Vol: 5, Pages: 14605-14637, ISSN: 2574-0962
Cui J, Daboczi M, Regue M, et al., 2022, 2D bismuthene as a functional interlayer between BiVO4 and NiFeOOH for enhanced oxygen-evolution photoanodes, Advanced Functional Materials, Vol: 32, Pages: 1-12, ISSN: 1616-301X
BiVO4 has attracted wide attention for oxygen-evolution photoanodes in water-splitting photoelectrochemical devices. However, its performance is hampered by electron-hole recombination at surface states. Herein, partially oxidized two-dimensional (2D) bismuthene is developed as an effective, stable, functional interlayer between BiVO4 and the archetypal NiFeOOH co-catalyst. Comprehensive (photo)electrochemical and surface photovoltage characterizations show that NiFeOOH can effectively increase the lifetime of photogenerated holes by passivating hole trap states of BiVO4; however, it is limited in influencing electron trap states related to oxygen vacancies (VO). Loading bismuthene on BiVO4 photoanodes increases the density of VO that are beneficial for the oxygen evolution reaction via the formation of oxy/hydroxyl-based water oxidation intermediates at the surface. Moreover, bismuthene increases interfacial band bending and fills the VO-related electron traps, leading to more efficient charge extraction. With the synergistic interaction of bismuthene and NiFeOOH on BiVO4, this composite photoanode achieves a 5.8-fold increase in photocurrent compared to bare BiVO4 reaching a stable 3.4 (±0.2) mA cm–2 at a low bias of +0.8 VRHE or 4.7(±0.2) mA cm–2 at +1.23 VRHE. The use of 2D bismuthene as functional interlayer provides a new strategy to enhance the performance of photoanodes.
Sena MS, Cui J, Baghdadi Y, et al., 2022, Lead-Free Halide Perovskite Cs<inf>2</inf>AgBiBr<inf>6</inf>/Bismuthene Composites for Improved CH<inf>4</inf> Production in Photocatalytic CO<inf>2</inf> Reduction, ACS Applied Energy Materials
CO2 photocatalytic conversion into value-added fuels through solar energy is a promising way of storing renewable energy while simultaneously reducing the concentration of CO2 in the atmosphere. Lead-based halide perovskites have recently shown great potential in various applications such as solar cells, optoelectronics, and photocatalysis. Even though they show high performance, the high toxicity of Pb2+ along with poor stability under ambient conditions restrains the application of these materials in photocatalysis. In this respect, we developed an in situ assembly strategy to fabricate the lead-free double perovskite Cs2AgBiBr6 on a 2D bismuthene nanosheet prepared by a ligand-assisted reprecipitation method for a liquid-phase CO2 photocatalytic reduction reaction. The composite improved the production and selectivity of the eight-electron CH4 pathway compared with the two-electron CO pathway, storing more of the light energy harvested by the photocatalyst. The Cs2AgBiBr6/bismuthene composite shows a photocatalytic activity of 1.49(±0.16) μmol g-1 h-1 CH4, 0.67(±0.14) μmol g-1 h-1 CO, and 0.75(±0.20) μmol g-1 h-1 H2, with a CH4 selectivity of 81(±1)% on an electron basis with 1 sun. The improved performance is attributed to the enhanced charge separation and suppressed electron-hole recombination due to good interfacial contact between the perovskite and bismuthene promoted by the synthesis method.
Eslava S, Hintermair U, 2021, Editorial: Recent advances in water splitting, CURRENT OPINION IN GREEN AND SUSTAINABLE CHEMISTRY, Vol: 32, ISSN: 2452-2236
Kumar S, Eslava S, 2021, Mechanochemically synthesized Pb-free halide perovskite-based Cs2AgBiBr6-Cu-RGO nanocomposite for photocatalytic CO2 reduction, Journal of Materials Chemistry A, Vol: 5/5/21, Pages: 12179-12187, ISSN: 2050-7488
Pb-based halide perovskites have recently showed great potential in various applications such as solar cells, optoelectronics and photocatalysis. Despite their high performance, the Pb2+ toxicity along with poor stability hinders long term applications in photocatalysis. Herein, we report mechanochemically prepared Pb-free Cs2AgBiBr6 double perovskite nanoplates and their heterostructure with Cu-loaded reduced graphene oxide (Cu–RGO) for gas-phase photocatalytic CO2 reduction using water vapor as the proton source in the absence of a hole scavenger. The resulting Cs2AgBiBr6–Cu–RGO nanocomposite shows significant photocatalytic activity of 10.7 (±0.6) μmol CH4 g−1 h−1, 1.9 (±0.3) μmol CO g−1 h−1 and 1.0 (±0.2) μmol H2 g−1 h−1, with a CH4 selectivity of 93.0 (±0.5)% on an electron basis with 1 sun and a remarkable apparent quantum efficiency of 0.89 (±0.21)% at 590 nm. A further 32% enhancement in photocatalytic activity on an electron basis is achieved when the light intensity is doubled (2 suns). The high performance was attributed to their improved charge separation and suppressed electron–hole recombination, along with extended visible light absorption, better stability in a humid environment and improved CO2 adsorption. These findings support Cs2AgBiBr6 as a potential Pb-free alternative to conventional halide perovskites for photocatalytic solar-to-fuel conversion and CO2 utilization.
Schukraft GEM, Woodward RT, Kumar S, et al., 2021, Hypercrosslinked polymers as a photocatalytic platform for visible-light-driven CO2 photoreduction using H2O, ChemSusChem: chemistry and sustainability, energy and materials, Vol: 14, Pages: 1720-1727, ISSN: 1864-5631
The design of robust, high‐performance photocatalysts is key for the success of solar fuel production by CO2 conversion. In this study, hypercrosslinked polymer (HCP) photocatalysts have been developed for the selective reduction of CO2 to CO, combining excellent CO2 sorption capacities, good general stabilities, and low production costs. HCPs are active photocatalysts in the visible light range, significantly outperforming the benchmark material, TiO2 P25, using only sacrificial H2O. It is hypothesized that superior H2O adsorption capacities facilitate access to photoactive sites, improving photocatalytic conversion rates when compared to sacrificial H2. These polymers are an intriguing set of organic photocatalysts, displaying no long‐range order or extended π‐conjugation. The as‐synthesized networks are the sole photocatalytic component, requiring no added cocatalyst doping or photosensitizer, representing a highly versatile and exciting platform for solar‐energy conversion.
Zhang J, Cui J, Eslava S, 2021, Oxygen evolution catalysts at transition metal oxide photoanodes: their differing roles for solar water splitting, Advanced Energy Materials, Vol: 11, Pages: 1-27, ISSN: 1614-6832
In the field of photoelectrochemical water splitting for hydrogen production, dedicated efforts have recently been made to improve water oxidation at photoanodes, and in particular, to accelerate the poor kinetics of the oxygen evolution reaction which is a key step in achieving a viable photocurrent density for industrialization. To this end, coating the photoanode semiconductors with oxygen evolution catalysts (OECs) has been one of the most popular options. The roles of OECs have been found to be multifold, as opposed to exclusively catalytic. This review aims to unravel the complexity of the interfacial processes arising from the material properties of both semiconductors and OECs, and to rationalize the variation in findings in the literature regarding the roles of OECs. Light is also shed on some of the most useful characterization techniques that probe the dynamics of photogenerated holes, to answer some of the field's most challenging mechanistic questions. Finally, some ideas and suggestions on the design principles of OECs are proposed.
Rood SC, Pastor-Algaba O, Tosca-Princep A, et al., 2021, Synergistic effect of simultaneous doping of ceria nanorods with Cu and Cr on CO oxidation and NO reduction, Chemistry: A European Journal, Vol: 27, Pages: 2165-2174, ISSN: 0947-6539
Ceria particles play a key role in catalytic applications such as automotive three-way catalytic systems in which toxic CO and NO are oxidized and reduced to safe CO2 and N2, respectively. In this work, we explore the incorporation of Cu and Cr metals as dopants in the crystal structure of ceria nanorods prepared by a single-step hydrothermal synthesis. XRD, Raman and XPS confirm the incorporation of Cu and Cr in the ceria crystal lattices, offering ceria nanorods with a higher concentration of oxygen vacancies. XPS also confirms the presence of Cr and Cu surface species. H2-TPR and XPS analysis show that the simultaneous Cu and Cr co-doping results in a catalyst with a higher surface Cu concentration and a much-enhanced surface reducibility, in comparison with either undoped or singly doped (Cu or Cr) ceria nanorods. While single Cu doping enhances catalytic CO oxidation and Cr doping improves catalytic NO reduction, co-doping with both Cu and Cr enhances the benefits of both dopants in a synergistic manner employing roughly a quarter of dopant weight.
Hammond OS, Atri RS, Bowron DT, et al., 2021, Structural evolution of iron forming iron oxide in a deep eutectic-solvothermal reaction, NANOSCALE, Vol: 13, Pages: 1723-1737, ISSN: 2040-3364
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- Citations: 8
Regue M, Ahmet IY, Bassi PS, et al., 2020, Zn-Doped Fe2TiO5 Pseudobrookite-Based Photoanodes Grown by Aerosol-Assisted Chemical Vapor Deposition, ACS APPLIED ENERGY MATERIALS, Vol: 3, Pages: 12066-12077, ISSN: 2574-0962
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- Citations: 10
Kumar N, Kumar S, Gusain R, et al., 2020, Polypyrrole-Promoted rGO-MoS2 Nanocomposites for Enhanced Photocatalytic Conversion of CO2 and H2O to CO, CH4, and H-2 Products, ACS APPLIED ENERGY MATERIALS, Vol: 3, Pages: 9897-9909, ISSN: 2574-0962
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- Citations: 29
Temerov F, Pham K, Juuti P, et al., 2020, Silver-Decorated TiO2 Inverse Opal Structure for Visible Light-Induced Photocatalytic Degradation of Organic Pollutants and Hydrogen Evolution, ACS APPLIED MATERIALS & INTERFACES, Vol: 12, Pages: 41200-41210, ISSN: 1944-8244
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- Citations: 28
Regue Grino M, Kumar S, Eslava S, 2020, Recent Advances in Photocatalytic Materials for Solar Fuel Production from Water and Carbon Dioxide, Heterogeneous Catalysis for Energy Applications, ISBN: 978-1-78801-718-3
In recent years, photocatalysis has received significant attention because of its clean way of converting water or carbon dioxide into sustainable chemical fuels, providing promising and viable routes to overcome both renewable energy demand and global climate change. This chapter focuses on recent progress in the design and synthesis of sustainable photocatalytic materials, namely novel metal oxides, perovskites, metal–organic frameworks, metal sulfides, layered double hydroxides and plasmonic and metal-free materials. Advances in the preparation of these photocatalysts are reviewed, revealing efficient strategies to enhance their photocatalytic activity to produce hydrogen and carbon-based fuels such as carbon monoxide and methane from inexhaustible water and carbon dioxide. Emphasis is given to the strategies that maximize the visible light absorption of the solar spectrum and charge separation and transfer; for example, through forming heterojunctions of nanostructured materials. This chapter also highlights various strategies adopted for improving not only the photoconversion efficiency, but also the selectivity of certain carbon-based fuels. Adopting these advances within the scientific community will ensure more rapid progress towards high solar to fuel conversions and future commercialization of photocatalytic devices.
Schukraft GM, Woodward R, Kumar S, et al., 2020, Hypercrosslinked Polymers as a Photocatalytic Platform for Visible-Light-Driven CO2 Photoreduction Using H2O
<jats:p>The design of robust, high-performance photocatalysts is key for the success of solar fuel production <jats:italic>via</jats:italic> CO<jats:sub>2</jats:sub>conversion. Herein, we present hypercrosslinked polymer (HCP) photocatalysts for the selective reduction of CO<jats:sub>2</jats:sub> to CO, combining excellent CO<jats:sub>2</jats:sub> sorption capacities, good general stabilities, and low production costs. HCPs are active photocatalysts in the visible light range, significantly out-performing the benchmark material, TiO<jats:sub>2</jats:sub> P25, using only sacrificial H<jats:sub>2</jats:sub>O. We hypothesise that superior H<jats:sub>2</jats:sub>O adsorption capacities led to concentration at photoactive sites, improving photocatalytic conversion rates when compared to sacrificial H<jats:sub>2</jats:sub>. These polymers are an intriguing set of organic photocatalysts, displaying no long-range order or extended pi-conjugation. The as-synthesised networks are the sole photocatalytic component, requiring no co-catalyst doping or photosensitiser, representing a highly versatile and exciting platform for solar-energy conversion.</jats:p>
Kumar S, Regue M, Isaacs M, et al., 2020, All-Inorganic CsPbBr3 nanocrystals: gram-scale mechanochemical synthesis and selective photocatalytic CO2 reduction to methane, ACS Applied Energy Materials, Vol: 3, Pages: 4509-4522, ISSN: 2574-0962
Halide perovskite CsPbBr3 has recently gained wide interest for its application in solar cells, optoelectronics and artificial photosynthesis, but further progress is needed to develop greener and more scalable synthesis procedures and for their application in humid environments. Herein, we report a fast and convenient mechanochemical synthesis of CsPbBr3 perovskite nanocrystals with scale-up capability and control over crystal size and morphology. These perovskite nanocrystals show excellent crystallinity and tunable morphologies, from nanorods to nanospheres and nanosheets, simply changing the mechanochemical reaction conditions such as ball milling time, ball size and Cs precursor. Furthermore, we explore their use for gas-phase photocatalytic CO2 reduction using water vapor as proton source. A photocatalytic conversion of CO2 and H2O(g) to 0.43 (0.03) μmol CH4 g-1 h-1, 2.25 (0.09) μmol CO g-1 h-1 and 0.08 (0.02) μmol H2 g-1 h-1 was for example achieved with CsPbBr3 nanosheets and simulated sunlight, keeping 30% of this activity over three consecutive cycles. When these CsPbBr3 nanosheets were mechanochemically prepared together with Cu-loaded reduced graphene oxide (Cu-RGO), the photocatalytic activity significantly improved to 12.7 (0.95) μmol CH4 g-1 h-1, 0.46 (0.11) μmol CO g-1 h-1 and 0.27 (0.02) μmol H2 g-1 h-1, and a 90% of this activity was retained over three consecutive cycles. The selectivity for CH4 increased to 98.5(0.93)% on an electron basis and a remarkable apparent quantum efficiency of 1.10(0.15)% at 523 nm was achieved. This enhanced activity, selectivity and stability were assigned to the better charge separation, visible light absorption, CO2 adsorption & activation, and hydrophobic character of the obtained composites. These results will contribute to the rational design and application of halide perovskites for CO2 photocatalytic reduction.
Freeman E, Kumar S, Thomas SR, et al., 2020, PrFeO3 Photocathodes Prepared Through Spray Pyrolysis, CHEMELECTROCHEM, Vol: 7, Pages: 1365-1372, ISSN: 2196-0216
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- Citations: 14
Rood S, Eslava S, Manigrasso A, et al., 2020, Recent advances in gasoline three-way catalyst formulation: A review, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING, Vol: 234, Pages: 936-949, ISSN: 0954-4070
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- Citations: 55
Regue M, Kumar S, Eslava S, 2020, CHAPTER 4: Recent Advances in Photocatalytic Materials for Solar Fuel Production from Water and Carbon Dioxide, RSC Energy and Environment Series, Pages: 80-115
In recent years, photocatalysis has received significant attention because of its clean way of converting water or carbon dioxide into sustainable chemical fuels, providing promising and viable routes to overcome both renewable energy demand and global climate change. This chapter focuses on recent progress in the design and synthesis of sustainable photocatalytic materials, namely novel metal oxides, perovskites, metal-organic frameworks, metal sulfides, layered double hydroxides and plasmonic and metal-free materials. Advances in the preparation of these photocatalysts are reviewed, revealing efficient strategies to enhance their photocatalytic activity to produce hydrogen and carbon-based fuels such as carbon monoxide and methane from inexhaustible water and carbon dioxide. Emphasis is given to the strategies that maximize the visible light absorption of the solar spectrum and charge separation and transfer; for example, through forming heterojunctions of nanostructured materials. This chapter also highlights various strategies adopted for improving not only the photoconversion efficiency, but also the selectivity of certain carbon-based fuels. Adopting these advances within the scientific community will ensure more rapid progress towards high solar to fuel conversions and future commercialization of photocatalytic devices.
Freeman E, Kumar S, Celorrio V, et al., 2019, Strategies for deposition of LaFeO3 photocathodes: improving photocurrent with a polymer template, Sustainable Energy and Fuels, Vol: 4, Pages: 884-894, ISSN: 2398-4902
Renewable and sustainable alternatives to fossil fuels are needed to limit the impact of global warming. Using metal oxide semiconductors as photoelectrodes within photoelectrochemical cell devices, in which solar energy can be stored and ultimately used for electricity generation, is one such alternative. LaFeO3 (LFO) has been shown to be an active photocathode on illumination of visible light but is restricted by low surface area and relatively low photocurrents achieved. The work herein utilizes a spin coating deposition method with a solution of nitrate precursors combined with non-ionic polymeric surfactant (Triton X-100). This allowed for the formation of a uniform porous LFO film of high coverage on a fluorine-doped tin oxide coated substrate, through directing growth and preventing particle aggregation during film fabrication. These porous LFO films achieved an enhanced photocurrent of -161±6 µA cm-2 at +0.43 VRHE, in addition to a remarkable high onset potential of +1.4 VRHE for cathodic photocurrent. It was additionally shown that this attained film quality and activity was superior to other film fabrication methods such as doctor blading and spray pyrolysis. With this polymer templating method for LFO films, not only are higher photocurrents achieved but there are also added benefits such as better charge separation, higher efficiencies, higher specific electrochemically-active surface area and improved stability.
Regue M, Sibby S, Ahmet IY, et al., 2019, TiO2 photoanodes with exposed {010} facets grown by aerosol-assisted chemical vapor deposition of a titanium oxo/alkoxy cluster, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 7, Pages: 19161-19172, ISSN: 2050-7488
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- Citations: 6
Zhang J, Eslava S, 2019, Understanding charge transfer, defects and surface states at hematite photoanodes, SUSTAINABLE ENERGY & FUELS, Vol: 3, Pages: 1351-1364, ISSN: 2398-4902
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- Citations: 39
Poli I, Hintermair U, Regue M, et al., 2019, Graphite-protected CsPbBr3 perovskite photoanodes functionalised with water oxidation catalyst for oxygen evolution in water, Nature Communications, Vol: 10, Pages: 1-10, ISSN: 2041-1723
Metal-halide perovskites have been widely investigated in the photovoltaic sector due to their promising optoelectronic properties and inexpensive fabrication techniques based on solution processing. Here we report the development of inorganic CsPbBr3-based photoanodes for direct photoelectrochemical oxygen evolution from aqueous electrolytes. We use a commercial thermal graphite sheet and a mesoporous carbon scaffold to encapsulate CsPbBr3 as an inexpensive and efficient protection strategy. We achieve a record stability of 30 h in aqueous electrolyte under constant simulated solar illumination, with currents above 2 mA cm−2 at 1.23 VRHE. We further demonstrate the versatility of our approach by grafting a molecular Ir-based water oxidation catalyst on the electrolyte-facing surface of the sealing graphite sheet, which cathodically shifts the onset potential of the composite photoanode due to accelerated charge transfer. These results suggest an efficient route to develop stable halide perovskite based electrodes for photoelectrochemical solar fuel generation.
Zhang Y, Kumar S, Marken F, et al., 2019, Pyro-electrolytic water splitting for hydrogen generation, 4th International Conference on Nanogenerator and Piezotronics (NGPT), Publisher: ELSEVIER SCIENCE BV, Pages: 183-191, ISSN: 2211-2855
Kumar S, Poli I, Isaacs MA, et al., 2019, Mechanochemical synthesis of all-Inorganic CsPbBr3 nanorods and their use in selective photocatalytic hydrogenation of CO2, National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Rood SC, Ahmet HB, Gomez-Ramon A, et al., 2019, Enhanced ceria nanoflakes using graphene oxide as a sacrificial template for CO oxidation and dry reforming of methane, APPLIED CATALYSIS B-ENVIRONMENTAL, Vol: 242, Pages: 358-368, ISSN: 0926-3373
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- Citations: 37
Walsh D, Zhang J, Regue M, et al., 2019, Simultaneous Formation of FeOx Electrocatalyst Coating within Hematite Photoanodes for Solar Water Splitting, ACS APPLIED ENERGY MATERIALS, Vol: 2, Pages: 2043-2052, ISSN: 2574-0962
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- Citations: 11
Castresana PA, Martinez SM, Freeman E, et al., 2019, Electricity generation from moss with light-driven microbial fuel cells, ELECTROCHIMICA ACTA, Vol: 298, Pages: 934-942, ISSN: 0013-4686
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- Citations: 12
Jo W-K, Kumar S, Eslava S, et al., 2018, Construction of Bi2WO6/RGO/g-C3N4 2D/2D/2D hybrid Z-scheme heterojunctions with large interfacial contact area for efficient charge separation and high-performance photoreduction of CO2 and H2O into solar fuels, APPLIED CATALYSIS B-ENVIRONMENTAL, Vol: 239, Pages: 586-598, ISSN: 0926-3373
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- Citations: 210
Regue M, Armstrong K, Walsh D, et al., 2018, Mo-doped TiO2 photoanodes using [Ti4Mo2O8(OEt)(10)](2) bimetallic oxo cages as a single source precursor, SUSTAINABLE ENERGY & FUELS, Vol: 2, Pages: 2674-2686, ISSN: 2398-4902
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- Citations: 12
Park MS, Walsh D, Zhang J, et al., 2018, Efficient hematite photoanodes prepared by hydrochloric acid-treated solutions with amphiphilic graft copolymer, JOURNAL OF POWER SOURCES, Vol: 404, Pages: 149-158, ISSN: 0378-7753
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- Citations: 7
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