A5005889599- Advanced Photocatalysis Techniques
- Electrocatalysts for Energy Conversion
- Advanced battery technologies research
- Copper-based nanomaterials and applications
- Electrochemical Analysis and Applications
- Perovskite Materials and Applications
- Gas Sensing Nanomaterials and Sensors
- Fuel Cells and Related Materials
- TiO2 Photocatalysis and Solar Cells
- Electronic and Structural Properties of Oxides
- Iron oxide chemistry and applications
- Conducting polymers and applications
- Ga2O3 and related materials
- Organic Electronics and Photovoltaics
- Metal-Organic Frameworks: Synthesis and Applications
- Ammonia Synthesis and Nitrogen Reduction
- Advanced Memory and Neural Computing
- Transition Metal Oxide Nanomaterials
- MXene and MAX Phase Materials
- 2D Materials and Applications
- ZnO doping and properties
- Chalcogenide Semiconductor Thin Films
- Catalytic Processes in Materials Science
- Hydrogen Storage and Materials
- Catalysis and Oxidation Reactions
Imperial College London
2017-2024
Imperial Valley College
2020-2023
Transnational Press London
2020
This study addresses the light intensity dependence of charge accumulation in a photocatalyst suspension, and its impact on both recombination kinetics steady-state H2 evolution efficiency. Cyanamide surface functionalized melon-type carbon nitride (NCNCNx) has been selected as an example emerging nitrides photocatalysts because excellent storage ability. Transient spectroscopic studies (from ps to s) show that bimolecular photogenerated electrons holes NCNCNx can be well described by random...
Oxygen vacancies are ubiquitous in metal oxides and critical to performance, yet the impact of these states upon charge carrier dynamics important for photoelectrochemical photocatalytic applications remains contentious poorly understood. A key challenge is unambiguous identification spectroscopic fingerprints which can be used track their function. Herein, we employ five complementary techniques modulate electronic occupancy associated with oxygen situ BiVO4 photoanodes, allowing us...
Abstract Understanding what controls the reaction rate on iridium-based catalysts is central to designing better electrocatalysts for water oxidation in proton exchange membrane electrolysers. Here we quantify densities of redox-active centres and probe their binding strengths amorphous IrO x rutile 2 using operando time-resolved optical spectroscopy. We establish a quantitative experimental correlation between intrinsic active-state energetics. find that adsorbed oxygen species, *O, formed...
Understanding the effect of noncovalent interactions intermediates at polarized catalyst–electrolyte interface on water oxidation kinetics is key for designing more active and stable electrocatalysts. Here, we combine operando optical spectroscopy, X-ray absorption spectroscopy (XAS), surface-enhanced infrared (SEIRAS) to probe oxygen evolution reaction (OER) activity IrOx in acidic alkaline electrolytes. Our results suggest that species OER (Ir4.x+–*O) binds much stronger compared with acid...
Abstract CO 2 photoreduction to C 1 /C 1+ energized molecules is a key reaction of solar fuel technologies. Building heterojunctions can enhance photocatalysts performance, by facilitating charge transfer between two heterojunction phases. The material parameters that control this remain unclear. Here, it hypothesized governing factors for in gas phase are: i) large porosity accumulate close catalytic sites and ii) high number “points contact” the components transfer. former requirement be...
ZnO/BiOI heterojunction photoanode thin films were prepared by aerosol-assisted chemical vapour deposition, and the impact of growth temperature film thickness on water oxidation functionality was systematically investigated. A top ZnO layer with a 120 nm (deposited at 350 °C) 390 thick BiOI 300 found to achieve best photoelectrochemical performance heterojunction. The exhibited significant increase in activity, photocurrent 0.27 mA·cm−2 observed 1.1 VRHE (350 nm, 2.58 mW·cm−2), which is ~...
The lithium-mediated system catalyzes nitrogen to ammonia under ambient conditions. Herein we discover that trace amount of water as an electrolyte additive─in contrast prior reports from the literature–can effect a dramatic improvement in Faradaic selectivity N2 reduction NH3. We report optimal concentration 35.9 mM and LiClO4 salt 0.8 M allows efficiency up 27.9 ± 2.5% at pressure. attribute increase incorporation Li2O solid interphase, suggested by our X-ray photoelectron spectroscopy...
Abstract Understanding the kinetic competition between charge extraction and recombination, how this is impacted by mobile ions, remains a key challenge in perovskite solar cells (PSCs). Here, issue addressed combining operando photoluminescence (PL) measurements, which allow measurement of real‐time PL spectra during current–voltage ( J–V ) scans under 1‐sun equivalent illumination, with results drift‐diffusion simulations. This analysis allows direct comparison internal performance...
A barrier to understanding the factors driving catalysis in oxygen evolution reaction (OER) is multiple overlapping redox transitions OER catalysts. The complexity of these obscure relationship between coverage adsorbates and kinetics, leading an experimental challenge measuring activity descriptors, such as binding energies, well adsorbate interactions, which may destabilize intermediates modulate their energies. Herein, we utilize a newly designed optical spectroelectrochemistry system...
Catalyst modification of metal oxide photoanodes can result in markedly improved water oxidation efficiency. However, the reasons for improvement are often subtle and controversial. Upon depositing a CoFe Prussian blue (CoFe-PB) catalyst on BiVO4, large photocurrent increase onset potential shift (up to 0.8 V) observed, resulting substantially more efficient system with high stability. To elucidate origin this enhancement, we used time-resolved spectroscopies compare dynamics photogenerated...
In this article we present the first comparative study of transient decay dynamics photo-generated charges for three polymorphs TiO2. To our knowledge, is such brookite phase TiO2 over timescales relevant to kinetics water splitting. We find that behavior brookite, both in relaxation and energetic distribution, similar anatase Moreover, links between rate recombination charge carriers, their distribution mode transport are made light findings used account differences splitting efficiency...
A limiting factor to the efficiency of water Oxygen Evolution Reaction (OER) in metal oxide nanoparticle photocatalysts is rapid recombination holes and electrons. Facet-engineering can effectively improve charge separation and, consequently, OER efficiency. However, kinetics behind this improvement remain poorly understood. This study utilizes photoinduced absorption spectroscopy investigate yield facet-engineered BiVO
Semiconductor/metal–organic framework (MOF) heterojunctions have demonstrated promising performance for the photoconversion of CO2 into value-added chemicals. To further improve performance, we must understand better factors which govern charge transfer across heterojunction interface. However, effects interfacial electric fields, can drive or hinder electron flow, are not commonly investigated in MOF-based heterojunctions. In this study, highlight importance band bending using two carbon...
Operando spectroelectrochemical analysis is used to determine the water oxidation reaction kinetics for hematite photoanodes prepared using four different synthetic procedures. While these exhibit very current/voltage performance, their underlying are found be almost invariant. Higher temperature thermal annealing was correlate with a shift in photocurrent onset potential toward less positive potentials, assigned suppression of both back electron-hole recombination and charge accumulation...
Nickel oxyhydroxide electrocatalysts are highly active for water oxidation and swell when electrochemically activated. In this thickness dependence study, we find only the upper surface (<5 nm) is during catalysis.
Recent work has shown that heterojunction photoelectrodes can achieve synergistically higher water splitting activity than their parent materials. To optimize the performance in such layered systems, it is necessary to develop new methods capable of assessing phase space. Herein, we explore WO3/TiO2 space as a model system. Using chemical vapor deposition, 71 unique photoanodes were grown (15 single-layer; 56 heterojunctions). The materials physically characterized using X-ray diffraction,...
MAX phases with the general formula Mn+1AXn are layered carbides, nitrides, and carbonitrides varying stacking sequence of layers M6X octahedra A element depending on n. While "211" MAXphases (n = 1) very common, higher n, especially n ≥ 3, have hardly been prepared. This work addresses open questions regarding synthesis conditions, structure, chemical composition "514" phase. In contrast to literature reports, no oxide is needed form phase, yet multiple heating steps at 1,600 °C required....
This study examines the kinetic origins of temperature dependence photoelectrochemical water oxidation on nanostructured titania photoanodes. We observe that photocurrent is enhanced at 50 °C relative to 20 °C, with this enhancement being most pronounced (by up 70%) low anodic potentials (<+0.6 V vs RHE). Over potential range, magnitude largely determined by competition between catalysis (WOC) and recombination surface holes bulk electrons (back electron–hole recombination, BER). quantify...
Bi-functional electrocatalysts capable of both the oxygen reduction reaction (ORR) and evolution (OER) are highly desirable for a variety renewable energy storage conversion technologies. To develop noble metal alternatives catalysis, non-noble compounds have been tremendously pursued but remain non-ideal to issues relating stability population number exposed active sites. Inspired by Engel-Brewer valence bond theory, strongly coupled nickel-cobalt-nitride solid-solution/carbon nanotube...
Nickel-based oxides and oxyhydroxide catalysts exhibit state-of-the-art activity for the sluggish oxygen evolution reaction (OER) under alkaline conditions. A widely employed strategy to increase gravimetric of catalyst is active surface area via nanostructuring or decrease particle size. However, fundamental understanding about how tuning these parameters influences density oxidized species their kinetics remains unclear. Here, we use solution combustion synthesis, a low-cost scalable...
The combination of a sol–gel precursor approach and microwave heating leads to hitherto unknown MAX phase Cr 2 GaC 1− x N . Magnetic measurements reveal that the susceptibility depends on nitrogen amount X-site.