Imperial College London

ProfessorMagdaTitirici

Faculty of EngineeringDepartment of Chemical Engineering

Chair in Sustainable Energy Materials
 
 
 
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Contact

 

+44 (0)20 7594 5601m.titirici

 
 
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Location

 

ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

361 results found

Yu S, He J, Zhang Z, Sun Z, Xie M, Xu Y, Bie X, Li Q, Zhang Y, Sevilla M, Titirici M-M, Zhou Het al., 2024, Towards Negative Emissions: Hydrothermal Carbonization of Biomass for Sustainable Carbon Materials., Adv Mater

The contemporary production of carbon materials heavily relies on fossil fuels, contributing significantly to the greenhouse effect. Biomass is a carbon-neutral resource whose organic carbon is formed from atmospheric CO2 . Employing biomass as a precursor for synthetic carbon materials can fix atmospheric CO2 into solid materials, achieving negative carbon emissions. Hydrothermal carbonization (HTC) presents an attractive method for converting biomass into carbon materials, by which biomass can be transformed into materials with favorable properties in a distinct hydrothermal environment, and these carbon materials have made extensive progress in many fields. However, the HTC of biomass is a complex and interdisciplinary problem, involving simultaneously the physical properties of the underlying biomass and sub/supercritical water, the chemical mechanisms of hydrothermal synthesis, diverse applications of resulting carbon materials, and the sustainability of the entire technological routes. This review starts with the analysis of biomass composition and distinctive characteristics of the hydrothermal environment. Then, the factors influencing the HTC of biomass, the reaction mechanism, and the properties of resulting carbon materials are discussed in depth, especially the different formation mechanisms of primary and secondary hydrochars. Furthermore, the application and sustainability of biomass-derived carbon materials are summarized, and some insights into future directions are provided.

Journal article

Xin X, Li Y, Zhang Y, Wang Y, Chi X, Wei Y, Diao C, Su J, Wang R, Guo P, Yu J, Zhang J, Sobrido AJ, Titirici M-M, Li Xet al., 2024, Large electronegativity differences between adjacent atomic sites activate and stabilize ZnIn2S4 for efficient photocatalytic overall water splitting., Nat Commun, Vol: 15

Photocatalytic overall water splitting into hydrogen and oxygen is desirable for long-term renewable, sustainable and clean fuel production on earth. Metal sulfides are considered as ideal hydrogen-evolved photocatalysts, but their component homogeneity and typical sulfur instability cause an inert oxygen production, which remains a huge obstacle to overall water-splitting. Here, a distortion-evoked cation-site oxygen doping of ZnIn2S4 (D-O-ZIS) creates significant electronegativity differences between adjacent atomic sites, with S1 sites being electron-rich and S2 sites being electron-deficient in the local structure of S1-S2-O sites. The strong charge redistribution character activates stable oxygen reactions at S2 sites and avoids the common issue of sulfur instability in metal sulfide photocatalysis, while S1 sites favor the adsorption/desorption of hydrogen. Consequently, an overall water-splitting reaction has been realized in D-O-ZIS with a remarkable solar-to-hydrogen conversion efficiency of 0.57%, accompanying a ~ 91% retention rate after 120 h photocatalytic test. In this work, we inspire an universal design from electronegativity differences perspective to activate and stabilize metal sulfide photocatalysts for efficient overall water-splitting.

Journal article

Li Y, Vasileiadis A, Zhou Q, Lu Y, Meng Q, Li Y, Ombrini P, Zhao J, Chen Z, Niu Y, Qi X, Xie F, van der Jagt R, Ganapathy S, Titirici MM, Li H, Chen L, Wagemaker M, Hu YSet al., 2024, Origin of fast charging in hard carbon anodes, Nature Energy

Transport electrification and grid storage hinge largely on fast-charging capabilities of Li- and Na-ion batteries, but anodes such as graphite with plating issues drive the scientific focus towards anodes with slopped storage potentials. Here we report fast charging of ampere-hour-level full Na-ion batteries within about 9 minutes for continuous 3,000 cycles based on hard carbon anodes. These anodes, in addition to displaying a sloped storage voltage, provide capacity at a nearly constant voltage just above the plating potential, without observing Na-metal plating under high areal capacity. Comparing the electrochemical behaviour of Li and Na in hard carbon through experimental and computational techniques, a unified storage mechanism relying on the dimensions of wedge nanopores and drawing parallels with underpotential deposition for metals is brought forward, providing a rational guide for achieving fast storage in hard carbon anodes.

Journal article

Li Y, Vasileiadis A, Zhou Q, Lu Y, Meng Q, Li Y, Ombrini P, Zhao J, Chen Z, Niu Y, Qi X, Xie F, van der Jagt R, Ganapathy S, Titirici MM, Li H, Chen L, Wagemaker M, Hu YSet al., 2024, Author Correction: Origin of fast charging in hard carbon anodes (Nature Energy, (2024), 10.1038/s41560-023-01414-5), Nature Energy

Correction to: Nature Energy, published online 3 January 2024. In the version of this article initially published, lithium (green, “Li”) and sodium (purple, “Na”) color key labels in Fig. 3a,d,e were interchanged and are now amended in the HTML and PDF versions of the article.

Journal article

Roy T, Goel S, Costa LT, Titirici M-M, Offer GJ, Marinescu M, Wang Het al., 2023, Strain induced electrochemical behaviors of ionic liquid electrolytes in an electrochemical double layer capacitor: Insights from molecular dynamics simulations., J Chem Phys, Vol: 159

Electrochemical Double Layer Capacitors (EDLCs) with ionic liquid electrolytes outperform conventional ones using aqueous and organic electrolytes in energy density and safety. However, understanding the electrochemical behaviors of ionic liquid electrolytes under compressive/tensile strain is essential for the design of flexible EDLCs as well as normal EDLCs, which are subject to external forces during assembly. Despite many experimental studies, the compression/stretching effects on the performance of ionic liquid EDLCs remain inconclusive and controversial. In addition, there is hardly any evidence of prior theoretical work done in this area, which makes the literature on this topic scarce. Herein, for the first time, we developed an atomistic model to study the processes underlying the electrochemical behaviors of ionic liquids in an EDLC under strain. Constant potential non-equilibrium molecular dynamics simulations are conducted for EMIM BF4 placed between two graphene walls as electrodes. Compared to zero strain, low compression of the EDLC resulted in compromised performance as the electrode charge density dropped by 29%, and the performance reduction deteriorated significantly with a further increase in compression. In contrast, stretching is found to enhance the performance by increasing the charge storage in the electrodes by 7%. The performance changes with compression and stretching are due to changes in the double-layer structure. In addition, an increase in the value of the applied potential during the application of strain leads to capacity retention with compression revealed by the newly performed simulations.

Journal article

Glatthaar C, Wang M, Wagner LQ, Breckwoldt F, Guo Z, Zheng K, Kriechbaum M, Amenitsch H, Titirici M-M, Smarsly BMet al., 2023, Lignin-Derived Mesoporous Carbon for Sodium-Ion Batteries: Block Copolymer Soft Templating and Carbon Microstructure Analysis., Chem Mater, Vol: 35, Pages: 10416-10433, ISSN: 0897-4756

The demand for versatile and sustainable energy materials is on the rise, given the importance of developing novel clean technologies for transition to a net zero economy. Here, we present the synthesis, characterization, and application of lignin-derived ordered mesoporous carbons with various pore sizes (from 5 to approximately 50 nm) as anodes in sodium-ion batteries. We have varied the pore size using self-synthesized PEOn-b-PHAm block copolymers with different PEO and PHA chain lengths, applying the "soft templating" approach to introduce isolated spherical pores of 20 to 50 nm in diameters. The pore structure was evaluated by transmission electron microscopy (TEM), nitrogen physisorption, and small-angle X-ray scattering (SAXS). We report the microstructure analysis of such mesoporous lignin-based carbons using Raman spectroscopy and wide-angle X-ray scattering (WAXS). In comparison with nontemplated carbon and carbons templated employing commercial Pluronic F-127 and PIB50-b-PEO45, which created accessible channels and spherical pores up to approximately 10 nm in diameter, the carbon microstructure analysis revealed that templating with all applied polymers significantly impedes graphitization upon thermal treatment. Furthermore, the gained knowledge of similar carbon microstructures regardless of the type of template allowed the investigation of the influence of different pore morphologies in carbon applied as an anode material in sodium-ion batteries, supporting the previous theories in the literature that closed pores are beneficial for sodium storage while providing insights into the importance of pore size.

Journal article

Deng H, Wang Z, Kim M, Yamauchi Y, Eichhorn SJ, Titirici MM, Deng Let al., 2023, Unleashing the power of capacitive deionization: Advancing ion removal with biomass-derived porous carbonaceous electrodes, Nano Energy, Vol: 117, ISSN: 2211-2855

Capacitive deionization (CDI) is a promising electrochemical technique for the removal and recycling of ions from micro-polluted wastewater but is still hindered by the co-ion expulsion effect and anode oxidation. In this study, these issues are addressed through optimization of both materials and electrochemical systems. A diverse set of porous carbons are prepared using biomass as a precursor and KOH as the activation agent. It is found that direct carbonization and/or KOH activation induce a negative surface charge, whereas intense nitrogen-doping results in an inverse surface charge for all biomass-derived carbons, characterized by the potential of zero charge (Epzc). Density functional theory calculations suggest that the carboxyl group and quaternary N contribute most among other functional groups to the negative and positive charges, respectively. A Epzc-matching asymmetric CDI system is constructed employing negatively charged and positively charged carbons as the cathode and anode, respectively. This configuration, coupled with precise optimization of the cathode-to-anode mass ratio (m-/m+), unlocks a high adsorption capacity of 17.2 mg g−1 for NaCl, surpassing the symmetric system by 84.7 %. Further fine tuning of the m-/m+ ratio results in a removal capacity of 167.4 mg g−1 for Cu2+ ions, which is the highest reported for carbonaceous materials to date.

Journal article

Pfersich J, Arauzo PJ, Modugno P, Titirici MM, Kruse Aet al., 2023, Evaluation of the Char Formation During the Hydrothermal Treatment of Wooden Balls, Global Challenges, Vol: 7

With wooden balls, a visualization of the hydrothermal carbonization to show the progress of the conversion to char is presented. In the present study, the balls represent the particles of biomass to investigate the differences in conversion outside and inside of biomass particles, during hydrothermal carbonization. A special focus is on hydrochar and pyrochar formation. The wooden balls are treated in subcritical water at 220 °C for holding times between 0 and 960 min. Even after 960 min, hydrolysis of the original biomass is incomplete as cellulose and hemicellulose are linked by lignin, inhibiting the reaction with water. Moreover, two different pathways of char production can be observed. Inside of the wooden ball pyrochar is formed as any water got that deep in, on the surface hydrochar is fixed, originated from the surrounding liquid. On the ground of the HTC reactor, a thin, brittle precipitate of likely hydrochar or humins can be found either from the precipitation of loosely attached compounds on the surface of the biomass or direct precipitation from the liquid.

Journal article

Gittins JW, Chen Y, Arnold S, Augustyn V, Balducci A, Brousse T, Frackowiak E, Gómez-Romero P, Kanwade A, Köps L, Jha PK, Lyu D, Meo M, Pandey D, Pang L, Presser V, Rapisarda M, Rueda-García D, Saeed S, Shirage PM, Ślesiński A, Soavi F, Thomas J, Titirici MM, Wang H, Xu Z, Yu A, Zhang M, Forse ACet al., 2023, Interlaboratory study assessing the analysis of supercapacitor electrochemistry data, Journal of Power Sources, Vol: 585, ISSN: 0378-7753

Supercapacitors are fast-charging energy storage devices of great importance for developing robust and climate-friendly energy infrastructures for the future. Research in this field has seen rapid growth in recent years, therefore consistent reporting practices must be implemented to enable reliable comparison of device performance. Although several studies have highlighted the best practices for analysing and reporting data from such energy storage devices, there is yet to be an empirical study investigating whether researchers in the field are correctly implementing these recommendations, and which assesses the variation in reporting between different laboratories. Here we address this deficit by carrying out the first interlaboratory study of the analysis of supercapacitor electrochemistry data. We find that the use of incorrect formulae and researchers having different interpretations of key terminologies are major causes of variability in data reporting. Furthermore we highlight the more significant variation in reported results for electrochemical profiles showing non-ideal capacitive behaviour. From the insights gained through this study, we make additional recommendations to the community to help ensure consistent reporting of performance metrics moving forward.

Journal article

Tort R, Bagger A, Westhead O, Kondo Y, Khobnya A, Winiwarter A, Davies BJV, Walsh A, Katayama Y, Yamada Y, Ryan MP, Titirici M-M, Stephens IELet al., 2023, Searching for the rules of electrochemical nitrogen fixation, ACS Catalysis, Vol: 13, Pages: 14513-14522, ISSN: 2155-5435

Li-mediated ammonia synthesis is, thus far, the only electrochemical method for heterogeneous decentralized ammonia production. The unique selectivity of the solid electrode provides an alternative to one of the largest heterogeneous thermal catalytic processes. However, it is burdened with intrinsic energy losses, operating at a Li plating potential. In this work, we survey the periodic table to understand the fundamental features that make Li stand out. Through density functional theory calculations and experimentation on chemistries analogous to lithium (e.g., Na, Mg, Ca), we find that lithium is unique in several ways. It combines a stable nitride that readily decomposes to ammonia with an ideal solid electrolyte interphase, balancing reagents at the reactive interface. We propose descriptors based on simulated formation and binding energies of key intermediates and further on hard and soft acids and bases (HSAB principle) to generalize such features. The survey will help the community toward electrochemical systems beyond Li for nitrogen fixation.

Journal article

Xu Y, Xie R, Li Q, Feng J, Luo H, Ye Q, Guo Z, Cao Y, Palma M, Chai G, Titirici M-M, Jones CRet al., 2023, Pyridine functionalized carbon nanotubes: unveiling the role of external pyridinic nitrogen sites for oxygen reduction reaction, Small, Vol: 19, Pages: 1-14, ISSN: 1613-6810

Pyridinic nitrogen has been recognized as the primary active site in nitrogen-doped carbon electrocatalysts for the oxygen reduction reaction (ORR), which is a critical process in many renewable energy devices. However, the preparation of nitrogen-doped carbon catalysts comprised of exclusively pyridinic nitrogen remains challenging, as well as understanding the precise ORR mechanisms on the catalyst. Herein, a novel process is developed using pyridyne reactive intermediates to functionalize carbon nanotubes (CNTs) exclusively with pyridine rings for ORR electrocatalysis. The relationship between the structure and ORR performance of the prepared materials is studied in combination with density functional theory calculations to probe the ORR mechanism on the catalyst. Pyridinic nitrogen can contribute to a more efficient 4-electron reaction pathway, while high level of pyridyne functionalization result in negative structural effects, such as poor electrical conductivity, reduced surface area, and small pore diameters, that suppressed the ORR performance. This study provides insights into pyridine-doped CNTs-functionalized for the first time via pyridyne intermediates-as applied in the ORR and is expected to serve as valuable inspiration in designing high-performance electrocatalysts for energy applications.

Journal article

Pedersen A, Bagger A, Barrio J, Maillard F, Stephens IEL, Titirici M-Met al., 2023, Atomic metal coordinated to nitrogen-doped carbon electrocatalysts for proton exchange membrane fuel cells: a perspective on progress, pitfalls and prospectives., J Mater Chem A Mater, Vol: 11, Pages: 23211-23222, ISSN: 2050-7488

Proton exchange membrane fuel cells require reduced construction costs to improve commercial viability, which can be fueled by elimination of platinum as the O2 reduction electrocatalyst. The past 10 years has seen significant developments in synthesis, characterisation, and electrocatalytic performance of the most promising alternative electrocatalyst; single metal atoms coordinated to nitrogen-doped carbon (M-N-C). In this Perspective we recap some of the important achievements of M-N-Cs in the last decade, as well as discussing current knowledge gaps and future research directions for the community. We provide a new outlook on M-N-C stability and atomistic understanding with a set of original density functional theory simulations.

Journal article

Pedersen A, Pandya J, Leonzio G, Serov A, Bernardi A, Stephens IEL, Titirici MM, Petit C, Chachuat Bet al., 2023, Comparative techno-economic and life-cycle analysis of precious versus non-precious metal electrocatalysts: the case of PEM fuel cell cathodes, Green Chemistry, Vol: 25, Pages: 10458-10471, ISSN: 1463-9262

Sluggish kinetics in the oxygen reduction reaction (ORR) require significant quantities of expensive Pt-based nanoparticles on carbon (Pt/C) at the cathode of proton exchange membrane fuel cells (PEMFCs). This catalyst requirement hinders their large-scale implementation. Single atom Fe in N-doped C (Fe-N-C) electrocatalysts offer the best non-Pt-based ORR activities to date, but their environmental impacts have not been studied and their production costs are rarely quantified. Herein, we report a comparative life-cycle assessment and techno-economic analysis of replacing Pt/C with Fe-N-C at the cathode of an 80 kW PEMFC stack. In the baseline scenario (20 gPt/Cvs. 690 gFe-N-C), we estimate that Fe-N-C could reduce damages on ecosystems and human health by 88-90% and 30-44%, respectively, while still increasing global warming potential by 53-92% and causing a comparable impact on resource depletion. The environmental impacts of Pt/C predominantly arise from the Pt precursor while those of Fe-N-C are presently dominated by the electricity consumption. The monetized costs of environmental externalities for both Fe-N-C and Pt/C catalysts exceed their respective direct production costs. Based on catalyst performance with learning curve analysis at 500 000 PEMFC stacks per annum, we estimate replacing Pt/C with Fe-N-C would increase PEMFC stack cost from 13.8 to 41.6 USD per kW. The cost increases despite a reduction in cathode catalyst production cost from 3.41 to 0.79 USD per kW (excluding environmental externalities). To be cost-competitive with a Pt-based PEMFC stack delivering 2020 US Department of Energy target of 1160 mW cm−2 (at 0.657 V), the same stack with an Fe-N-C cathode would need to reach 874 mW cm−2, equivalent to a 200% performance improvement. These findings demonstrate the need for continued Fe-N-C activity development with sustainable synthesis routes in mind to replace Pt-based cathode catalyst in PEMFCs. Based on forecasting scenarios of

Journal article

Favero S, Stephens IEL, Titirci M-M, 2023, Anion Exchange Ionomers: Design Considerations and Recent Advances - An Electrochemical Perspective., Adv Mater

Alkaline-based electrochemical devices, such as anion exchange membrane (AEM) fuel cells and electrolyzers, are receiving increasing attention. However, while the catalysts and membrane are methodically studied, the ionomer is largely overlooked. In fact, most of the studies in alkaline electrolytes are conducted using the commercial proton exchange ionomer Nafion. The ionomer provides ionic conductivity; it is also essential for gas transport and water management, as well as for controlling the mechanical stability and the morphology of the catalyst layer. Moreover, the ionomer has distinct requirements that differ from those of anion-exchange membranes, such as a high gas permeability, and that depend on the specific electrode, such as water management. As a result, it is necessary to tailor the ionomer structure to the specific application in isolation and as part of the catalyst layer. In this review, an overview of the current state of the art for anion exchange ionomers is provided, summarizing their specific requirements and limitations in the context of AEM electrolyzers and fuel cells.

Journal article

Zhang H, Diao J, Liu Y, Zhao H, Ng BKY, Ding Z, Guo Z, Li H, Jia J, Yu C, Xie F, Henkelman G, Titirici M-M, Robertson J, Nellist P, Duan C, Guo Y, Riley DJ, Qiu Jet al., 2023, In-situ grown Cu dendrites plasmonically enhance electrocatalytic hydrogen evolution on facet-engineered Cu₂O, Advanced Materials, Vol: 35, ISSN: 0935-9648

Electrocatalytic hydrogen evolution reaction (HER) is widely regarded as one of the most efficient and sustainable strategies for hydrogen production. Up to now, most electrocatalysis research related to HER mainly focuses on stand-alone electrocatalysis and fails to pay attention to the integration of other driving forces such as light. Herein, Cu2 O nanostructures with different exposed crystal facets were synthesized by wet chemical methods for electrocatalytic HER, and it was found that the octahedral Cu2 O nanostructures with exposed crystal planes of (111) (O-Cu2 O) had the best hydrogen evolution performance. Density functional theory (DFT) calculations found that the better HER performance on Cu2 O (111) facets was attributed to the lower energy barrier in the Heyrovsky step. Operando Raman spectroscopy and ex-situ characterization techniques showed that Cu2 O was reduced during HER, in which Cu dendrites were grown on the surface of the Cu2 O nanostructures, resulting in the better HER performance of O-Cu2 O after HER (O-Cu2 O-A) compared with that of the as-prepared O-Cu2 O. DFT calculations indicated that the charge transfer at the Cu2 O/Cu interface enhanced its surface electron concentration. Under illumination, the onset potential of O-Cu2 O-A is ca. 52 mV positive than that of O-Cu2 O, which is induced by the plasmon-activated electrochemical system consisting of Cu2 O and the in-situ generated Cu dendrites. Incident photon-to-current efficiency (IPCE) measurements, ultraviolet-visible (UV-Vis) spectroscopy and X-ray photoelectron spectroscopy (XPS) demonstrate the hot electron injection (HEI) from Cu dendrites to Cu2 O. Ab initio nonadiabatic molecular dynamics (NAMD) simulations revealed that the transfer of photogenerated electrons (27 fs) from Cu dendrites to Cu2 O nanostructures is faster than electron relaxation (170 fs), enhancing its surface plasmons activity, and the HEI of Cu dendrites increases the charge density of Cu2 O. These make t

Journal article

Ouyang M, Guo Z, Salinas Farran L, Zhao S, Zhao Y, Titirici M, Brandon Net al., 2023, Co-Electrospin-Electrosprayed High Areal-Loading Sodium-Ion Battery Electrodes, 244th ECS Meeting

Conference paper

Sarma SC, Barrio J, Bagger A, Pedersen A, Gong M, Luo H, Wang M, Favero S, Zhao C, Zhang Q, Kucernak A, Titirici M, Stephens IELet al., 2023, Reaching the fundamental limitation in CO2 reduction to CO with single atom catalysts, Advanced Functional Materials, Vol: 33, ISSN: 1616-301X

The electrochemical CO2 reduction reaction (CO2RR) to value-added chemicals with renewable electricity is a promising method to decarbonize parts of the chemical industry. Recently, single metal atoms in nitrogen-doped carbon (MNC) have emerged as potential electrocatalysts for CO2RR to CO with high activity and faradaic efficiency, although the reaction limitation for CO2RR to CO is unclear. To understand the comparison of intrinsic activity of different MNCs, two catalysts are synthesized through a decoupled two-step synthesis approach of high temperature pyrolysis and low temperature metalation (Fe or Ni). The highly meso-porous structure results in the highest reported electrochemical active site utilization based on in situ nitrite stripping; up to 59±6% for NiNC. Ex situ X-ray absorption spectroscopy (XAS) confirms the penta-coordinated nature of the active sites. The catalysts are amongst the most active in the literature for CO2 reduction to CO. The density functional theory calculations (DFT) show that their binding to the reaction intermediates approximates to that of Au surfaces. However, it is found that the turnover frequencies (TOFs) of the most active catalysts for CO evolution converge, suggesting a fundamental ceiling to the catalytic rates.

Journal article

Tahir A, Haq TU, Basra FR, Duran H, Briscoe J, Wang M, Titirici M-M, Hussain I, Rehman HUet al., 2023, Correction to “Electronic and Surface Modifications of Ni–Co–Fe Oxides: A Catalyst with Maximum Exposure of Fe Active Sites for Water Electrolysis”, ACS Applied Engineering Materials, Vol: 1, Pages: 2450-2450, ISSN: 2771-9545

Journal article

Sarma SC, Barrio J, Gong M, Pedersen A, Kucernak A, Titirici M, Stephens IELet al., 2023, Atomically dispersed Fe in a C2N-derived matrix for the reduction of CO2 to CO, Electrochimica Acta, Vol: 463, ISSN: 0013-4686

Carbon-supported single metal atoms coordinated to nitrogen have recently emerged as efficient electrocatalysts for the electrochemical CO2 reduction reaction (CO2RR) to CO; although the presence of aggregated metallic species can decrease Faradaic efficiency, catalyst utilization and promote the hydrogen evolution reaction. In this work, we employ our recent synthetic protocol for producing single and dual Fe atoms in a high surface area C2N-derived nitrogen-doped carbon and test the catalysts for CO2 reduction. The higher resolution of the X-ray absorption spectroscopy that we employed herein, relative to our previous report, allowed us to more accurately pinpoint the dominant site as pentacoordinated Fe single atoms. The material displays high active site utilization of 25.1 ± 1.2% (based on in situ nitrite stripping experiments). Additionally, a Faradaic efficiency of 98% for the CO2RR to CO was obtained, with a turnover frequency of 2.5 e− site−1 s−1, at -0.56 V vs a reversible hydrogen electrode (RHE); on par with state-of-the-art Au catalysts.

Journal article

Guo Z, Xu Z, Xie F, Jiang J, Zheng K, Alabidun S, Crespo-Ribadeneyra M, Hu Y-S, Au H, Titirici M-Met al., 2023, Investigating the Superior Performance of Hard Carbon Anodes in Sodium-Ion Compared With Lithium- and Potassium-Ion Batteries, ADVANCED MATERIALS, ISSN: 0935-9648

Journal article

Favero S, Stephens IEL, Titirici M-M, 2023, Deconvoluting kinetics and transport effects of ionic liquid layers on FeN4-based oxygen reduction catalysts, EES Catalysis, Vol: 1, Pages: 742-754, ISSN: 2753-801X

The use of ionic liquid layers has been reported to improve both the activity and durability of several oxygen reduction catalysts. However, the development of this technology has been hindered by the lack of understanding of the mechanism behind this performance enhancement. In this work, we use a library of ionic liquids to modify a model FeN4 catalyst (iron phthalocyanine), to decouple the effects of ionic liquid layers on oxygen reduction kinetics and oxygen transport. Our results show that oxygen reduction activity at low overpotentials it determined by the ionic liquids’ influence on the *OH binding energy on the active sites, while oxygen solubility and diffusivity controls transport at high overpotentials. Finally, using nitrogen physisorption, we have demonstrated that the distribution of the ionic liquids on the catalyst is inhomogeneous, and depends on the nature of the ionic liquid used.

Journal article

Dadsetan M, Latham KG, Kumral B, Khan MF, Scott M, Mitra T, Naseri A, Manzoor S, Bobicki ER, Filleter T, Titirici MM, Thomson MJet al., 2023, Carbon film produced from microwave-driven methane pyrolysis, Carbon Trends, Vol: 12

Methane pyrolysis is a widely used technique for producing hydrogen and valuable carbon materials. Among these materials are carbon films, which have a diverse range of properties that make them useful for various applications. This study focuses on synthesizing a new type of carbon film through a microwave-driven methane pyrolysis process. The resulting metallic-like carbon film deposits on a polished quartz substrate and detaches as it thickens. We conducted a thorough characterization of the film's properties, using different techniques to study its surface morphology and structural features. Our findings show that the carbon film has a smooth surface texture and a semi-graphitic internal structure, with 78% of the carbon atoms exhibiting sp2 bonding as revealed by X-ray photoelectron spectroscopy. X-ray diffraction analysis further confirms the presence of microcrystalline carbon fragments within the film. Additionally, conductivity measurements using a conductive-atomic force microscope demonstrate the carbon film's remarkable electrical conductivity, comparable to that of gold and silver metals. The electrochemical measurements indicate that the carbon film's high conductivity and free-standing nature make it a promising candidate for use as a direct active material in sodium-ion batteries. This is because the film does not require binders or conductive agents, which can improve battery performance.

Journal article

Dadsetan M, Latham KG, Khan MF, Zaher MH, Manzoor S, Bobicki ER, Titirici M-M, Thomson MJet al., 2023, Characterization of carbon products from microwave-driven methane pyrolysis, CARBON TRENDS, Vol: 12, ISSN: 2667-0569

Journal article

Tahir A, Haq TU, Rafique Basra F, Duran H, Briscoe J, Wang M, Titirici M-M, Hussain I, Rehman HUet al., 2023, Electronic and Surface Modifications of Ni–Co–Fe Oxides: A Catalyst with Maximum Exposure of Fe Active Sites for Water Electrolysis, ACS Applied Engineering Materials, Vol: 1, Pages: 1698-1710, ISSN: 2771-9545

Journal article

Mukadam Z, Liu S, Pedersen A, Barrio J, Fearn S, Sarma SC, Titirici M-M, Scott SB, Stephens IEL, Chan K, Mezzavilla Set al., 2023, Furfural electrovalorisation using single-atom molecular catalysts, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 16, Pages: 2934-2944, ISSN: 1754-5692

Journal article

Liu S, Mukadam Z, Scott SB, Sarma SC, Titirici M-M, Chan K, Govindarajan N, Stephens IEL, Kastlunger Get al., 2023, Unraveling the reaction mechanisms for furfural electroreduction on copper., EES Catal, Vol: 1, Pages: 539-551

Electrochemical routes for the valorization of biomass-derived feedstock molecules offer sustainable pathways to produce chemicals and fuels. However, the underlying reaction mechanisms for their electrochemical conversion remain elusive. In particular, the exact role of proton-electron coupled transfer and electrocatalytic hydrogenation in the reaction mechanisms for biomass electroreduction are disputed. In this work, we study the reaction mechanism underlying the electroreduction of furfural, an important biomass-derived platform chemical, combining grand-canonical (constant-potential) density functional theory-based microkinetic simulations and pH dependent experiments on Cu under acidic conditions. Our simulations indicate the second PCET step in the reaction pathway to be the rate- and selectivity-determining step for the production of the two main products of furfural electroreduction on Cu, i.e., furfuryl alcohol and 2-methyl furan, at moderate overpotentials. We further identify the source of Cu's ability to produce both products with comparable activity in their nearly equal activation energies. Furthermore, our microkinetic simulations suggest that surface hydrogenation steps play a minor role in determining the overall activity of furfural electroreduction compared to PCET steps due to the low steady-state hydrogen coverage predicted under reaction conditions, the high activation barriers for surface hydrogenation and the observed pH dependence of the reaction. As a theoretical guideline, low pH (<1.5) and moderate potential (ca. -0.5 V vs. SHE) conditions are suggested for selective 2-MF production.

Journal article

Kim H-K, Yu A, Titirici M, Merlet C, Gao Y, Wang Jet al., 2023, Materials challenges for supercapacitors, APL MATERIALS, Vol: 11, ISSN: 2166-532X

Journal article

Westhead O, Spry M, Bagger A, Shen Z, Yadegari H, Favero S, Tort R, Titirici M, Ryan MP, Jervis R, Katayama Y, Aguadero A, Regoutz A, Grimaud A, Stephens IELet al., 2023, The role of ion solvation in lithium mediated nitrogen reduction, Journal of Materials Chemistry A, Vol: 11, Pages: 12746-12758, ISSN: 2050-7488

Since its verification in 2019, there have been numerous high-profile papers reporting improved efficiency of lithium-mediated electrochemical nitrogen reduction to make ammonia. However, the literature lacks any coherent investigation systematically linking bulk electrolyte properties to electrochemical performance and Solid Electrolyte Interphase (SEI) properties. In this study, we discover that the salt concentration has a remarkable effect on electrolyte stability: at concentrations of 0.6 M LiClO4 and above the electrode potential is stable for at least 12 hours at an applied current density of −2 mA cm−2 at ambient temperature and pressure. Conversely, at the lower concentrations explored in prior studies, the potential required to maintain a given N2 reduction current increased by 8 V within a period of 1 hour under the same conditions. The behaviour is linked more coordination of the salt anion and cation with increasing salt concentration in the electrolyte observed via Raman spectroscopy. Time of flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy reveal a more inorganic, and therefore more stable, SEI layer is formed with increasing salt concentration. A drop in faradaic efficiency for nitrogen reduction is seen at concentrations higher than 0.6 M LiClO4, which is attributed to a combination of a decrease in nitrogen solubility and diffusivity as well as increased SEI conductivity as measured by electrochemical impedance spectroscopy.

Journal article

Hongrutai N, Nganglumpoon R, Watmanee S, Pinthong P, Szilagyi PA, Titirici M-M, Panpranot Jet al., 2023, <i>In</i><i>-situ</i> electrodeposited Ag/Cu for electrochemical reduction of acetic acid to nanodiamond under ambient conditions, MATERIALS TODAY CHEMISTRY, Vol: 30, ISSN: 2468-5194

Journal article

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