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Quantifying Photocurrent Loss of a Single Particle–Particle Interface in Nanostructured Photoelectrodes
摘要： Particle?particle interfaces are ubiquitous in nanostructured photoelectrodes and photovoltaics, which are important devices for solar energy conversion. These interfaces are expected to cause performance losses in these devices, but how much loss they would incur is poorly defined. Here we use a subparticle photoelectrochemical microscopy approach in combination with specific photocurrent measurement electrode configurations to quantify the current losses from single particle?particle interfaces formed between individual TiO2 nanorods operating as photoanodes in aqueous electrolytes. We find that a single interface leads to ～20% photocurrent loss (i.e., ～80% retention of the original current). Such quantitative, first-of-its-kind, information provides a metric for guiding the optimization and design of nanostructured photoelectrodes and photovoltaics.
关键词： single nanorod photoelectrodes,interface losses,Subparticle photoelectrochemistry
更新于2025-09-23 15:23:52
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Scaling up electrodes for photoelectrochemical water splitting: fabrication process and performance of 40 cm2 LaTiO2N photoanodes
摘要： A scalable process for particle-based photoanodes is developed. The electrodes are versatilely made of photocatalytically active semiconductor particles, here LaTiO2N, and optionally coated with co-catalysts and protecting components, all immobilized on a conducting substrate. The involved fabrication steps are restricted to scalable processes like electrophoretic deposition, annealing in air and dip coating. Special care is taken to ensure charge transport in between particles and to the substrate by adding conducting connectors. Adapting the fabrication steps, the geometrical electrode dimension is increased from the size of a typical lab electrode of 1 cm2 to 40 cm2. The quality of the scale up process is characterized by comparing the photoanodes in terms of thickness, light absorption properties and morphology. For several compositions, the electrochemical performance of both electrode sizes is assessed by measuring photocurrents and Faraday efficiencies. The comparison revealed a complex upscaling behavior and showed that photoelectrode size affected performance already on the 0.1 m scale.
关键词： photoelectrodes,energy conversion,LaTiO2N,electrode size,water splitting
更新于2025-09-23 15:22:29
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Multi-layered WO3 nano-platelets for efficient photoelectrochemical water splitting: the role of the annealing ramp
摘要： Multi-layered WO3 nano-square platelets films were successfully grown on transparent TCO substrates by spray-coating of WO3 nanoparticles aqueous suspension prepared by the sol-gel method. This work assesses the influence of two annealing schemes in the photo-response of WO3 photoelectrodes with different film thicknesses. The photoelectrochemical characterization reveals that the slow-heating ramp produces a photoelectrode with an improved photocurrent density of 1.6 mA·cm-2 at 1.23 V vs RHE. Comparing photoelectrodes with the same film thickness, the slow-heating ramp yield higher photocurrent densities; 80 % more than the conventional fast-heating ramp. The effect of the annealing ramp on the morphology and crystalline-phase structure of WO3 photoelectrodes is correlated with the photocurrent density. The slow-heating ramp annealing unveils film morphology with both, higher porosity degree and higher nano-square platelets dimensions. DRX structural analyses disclose that the films grow in monoclinic crystalline phase with a textural preferential direction [002], often related to improved photocurrent performances. The crystallite sizes and lattice microstrain are estimated using a simple X-ray diffraction broadening method, the Williamson-Hall analysis. A quantified correlation between the WO3 lattice defects, intergrains strain and performance is performed. The proposed deposition method paves the way for producing efficient and scalable photoelectrodes of WO3 for photoelectrochemical water splitting by using low-cost and simple manufacturing processes.
关键词： annealing ramp,X-ray peak broadening,tungsten trioxide,nano-platelets,photoelectrochemical cells,photoelectrodes
更新于2025-09-23 15:22:29
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Why and how carbon dioxide conversion to methanol happens on functionalized semiconductor photoelectrodes
摘要： Functionalization of semiconductor electrode surfaces with adsorbed 2-pyridinide (2-PyH–*) has been postulated to enable selective CO2 photo-electro-reduction to CH3OH. This hypothesis is supported by recent estimates of sufficient 2-PyH–* lifetimes and low barriers for hydride transfer (HT) to CO2. However, the complete mechanism for reducing CO2 to CH3OH remained unidentified. Here, vetted quantum chemistry protocols for modeling GaP reveal a pathway involving HTs to specific CO2 reduction intermediates. Predicted barriers suggest that HT to HCOOH requires adsorbed HCOOH* reacting with 2-PyH–*, a new catalytic role for the surface. HT to HCOOH* produces CH2(OH)2 but subsequent HT to CH2(OH)2 forming CH3OH is hindered. However, CH2O, dehydrated CH2(OH)2, easily reacts with 2-PyH–* producing CH3OH. Further reduction of CH3OH to CH4 via HT from 2-PyH–* encounters a high barrier, consistent with experiment. Our finding that the GaP surface enables HT to HCOOH* explains why the primary CO2 reduction product over CdTe photoelectrodes is HCOOH rather than methanol, as HCOOH does not adsorb on CdTe and so the reaction terminates. The stability of 2-PyH–* (vs. its protonation product DHP*), the relative dominance of CH2(OH)2 over CH2O, and the required desorption of CH2(OH)2* are the most likely limiting factors, explaining the low yield of CH3OH observed experimentally.
关键词： hydride transfer,CO2 reduction,semiconductor,photoelectrodes,methanol
更新于2025-09-23 15:21:01
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Grain Boundaries Limit the Charge Carrier Transport in Pulsed Laser Deposited ?±-SnWO <sub/>4</sub> Thin Film Photoabsorbers
摘要： Recently, α-SnWO4 attracted attention as a material to be used as a top absorber in a tandem device for photoelectrochemical water splitting due to its nearly optimum bandgap of ~1.9?eV and an early photocurrent onset potential of ~0 V vs. RHE. However, the mismatch between the charge carrier diffusion length and light penetration depth—which is typical for metal oxide semiconductors—currently hinders the realization of high photoconversion efficiencies. In this work, the pulsed laser deposition process and annealing treatment of α-SnWO4 thin films are elucidated in order to optimize their charge carrier transport properties. A high temperature treatment is found to enhance the photoconductivity of α-SnWO4 by more than one order of magnitude, as measured with time-resolved microwave conductivity (TRMC). A complimentary analysis by time-resolved terahertz spectroscopy (TRTS) shows that this improvement can be assigned to an increase of the grain size in the heat-treated films. In addition, TRTS reveals electron-hole charge carrier mobilities of up to 0.13 cm2 V-1s-1 in α-SnWO4. This is comparable to values found for BiVO4, which is one of the best performing metal oxide photoanode materials to date. These findings show that there is a significant potential for further improving the properties of α-SnWO4 photoanodes.
关键词： α-SnWO4,metal oxide photoelectrodes,grain boundaries,charge carrier dynamics,pulsed laser deposition
更新于2025-09-23 15:19:57
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Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide
摘要： Nanostructured TiO2 and graphene-based materials constitute components of actual interest in devices related to solar energy conversion and storage. In this work, we show that a thin layer of electrochemically reduced graphene oxide (ECrGO), covering nanostructured TiO2 photoelectrodes, can significantly improve the photoactivity. In order to understand the working principle, ECrGO/TiO2 photoelectrodes with different ECrGO thicknesses were prepared and studied by a set of photoelectrochemical measurements. Methanol in alkaline conditions was employed as effective hole acceptor probe to elucidate the electronic phenomena in the electrode layers and interfaces. These studies underline the hole accepting properties of ECrGO and reveal the formation of a p-n junction at the interface between ECrGO and TiO2. It is shown for the first time that the resulting space charge region of about 10 nm defines the operational functionality of the ECrGO layer. Films thinner than the space charge region act as hole transport layer (HTL), which efficiently transfers holes to the liquid interface thus leading to enhanced photoactivity. Thicker films however act as hole blocking layer (HBL), resulting in a systematic decrease of the photoactivity. The finding of a thickness dependent threshold value for the operation of ECrGO as HTL and HBL is of general interest for the fabrication of optoelectronic devices with improved performance.
关键词： reduced graphene oxide,photoelectrodes,titanium dioxide,photoelectrochemistry,hole-transport layer
更新于2025-09-23 15:19:57
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Elucidating the Pulsed Laser Deposition Process of BiVO <sub/>4</sub> Photoelectrodes for Solar Water Splitting
摘要： BiVO4 thin films for the use as photoelectrodes for solar water splitting are prepared by pulsed laser deposition (PLD), a powerful technique to synthesize compact multinary metal oxides films with a high electronic quality. Here, the PLD process of BiVO4 films by ablating a BiVO4 target is systematically elucidated with a special focus on deviations from an ideal stoichiometric target-to-substrate material transfer. By correlating the V:Bi ratio of the films with their charge carrier transport properties and PEC performance, AM1.5 sulfite oxidation photocurrents of ~2.4 mA cm-2 at E = 1.23 V vs. RHE with stoichiometric films are achieved without any deliberate doping or surface modification. In addition, we prepare BiVO4 photoelectrodes for the first time by the alternating ablation of Bi2O3 and V2O5 targets. This approach is found to be an attractive alternative route to control the cation stoichiometry and produces BiVO4 films that generate AM1.5 sulfite oxidation photocurrents of up to 2.6?mA cm-2 at E = 1.23 V vs. RHE. Our results provide important insights into the PLD process of ternary oxide semiconductors and help to accelerate the synthesis and investigation of new multinary metal oxide photoelectrodes.
关键词： pulsed laser deposition,solar water splitting,stoichiometry,BiVO4,photoelectrodes
更新于2025-09-19 17:13:59
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Modulating Charge Separation Efficiency of Water Oxidation Photoanodes with Polyelectrolyte‐Assembled Interfacial Dipole Layers
摘要： The charge separation efficiency of water oxidation photoanodes is modulated by depositing polyelectrolyte multilayers on their surface using layer-by-layer (LbL) assembly. The deposition of the polyelectrolyte multilayers of cationic poly(diallyldimethylammonium chloride) and anionic poly(styrene sulfonate) induces the formation of interfacial dipole layers on the surface of Fe2O3 and TiO2 photoanodes. The charge separation efficiency is modulated by tuning their magnitude and direction, which in turn can be achieved by controlling the number of bilayers and type of terminal polyelectrolytes, respectively. Specifically, the multilayers terminated with anionic poly(styrene sulfonate) exhibit a higher charge separation efficiency than those with cationic counterparts. Furthermore, the deposition of water oxidation molecular catalysts on top of interfacial dipole layers enables more efficient photoelectrochemical water oxidation. The approach exploiting the polyelectrolyte multilayers for improving the charge separation efficiency is effective regardless of pH and types of photoelectrodes. Considering the versatility of the LbL assembly, it is anticipated that this study will provide insights for the design and fabrication of efficient photoelectrodes.
关键词： interfacial dipole,polyelectrolyte multilayers,charge separation,photoelectrodes
更新于2025-09-16 10:30:52
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Preparation and characterization of hematite nanoparticles-decorated zinc oxide particles (ZnO/Fe2O3) as photoelectrodes for solar cell applications
摘要： Because of the socio-environmental and economic impacts of the use of fossil fuels, the demand for the diversi?cation of the energy matrix has increased. Energy devices utilizing renewable energy such as solar cells stand out as a possible solution to this problem. Therefore, in order to realize the practical applications of solar cells, it is imperative to develop novel structural materials and to optimize the properties of the existing ones. In this study, we prepared a photoelectrode using hematite-decorated zinc oxide particles (ZnO/Fe2O3). The ?eld-emission scanning electron microscopy and Brunauer–Emmett–Teller results con?rmed that Fe2O3 coated the surface of the ZnO particles and improved their photoelectrochemical properties. The composite was found to be a promising photoelectrode for solar cells.
关键词： Hematite nanoparticles,Photoelectrodes,Zinc oxide particles,Solar cell applications,Energy materials
更新于2025-09-11 14:15:04
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Fabrication of photoactive CaTiO3–TiO2 composite thin film electrodes via facile single step aerosol assisted chemical vapor deposition route
摘要： CaTiO3–TiO2 composite oxide films have been employed, for the first time, as photoelectrodes in photoelectrochemical (PEC) splitting of water. The transparent methanol solutions of Ti(Pro)4 and newly synthesized calcium complex [Ca2(TFA)3(OAc)(PrOH)(H2O)(THF)3] (1) (where TFA stands for trifluoroacetato; OAc stands for acetate; and PrOH stands for isopropanol) were utilized for aerosol assisted chemical vapor deposition (AACVD) of the target films. The composite electrodes were deposited on fluorine doped tin oxide (FTO) coated conducting glass substrates at varying deposition temperatures of 500–600 °C. The resulting films were extensively characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray analysis and scanning electron microscopy. PEC responses of all the composite electrodes were studied under simulated solar irradiation of AM 1.5 G (100 mW cm?2). The CaTiO3–TiO2 photoanode formed at 600 °C showed higher photocurrent density of 610 μA cm?2 at 0.7 V versus Ag/AgCl/3 M KCl reference electrode as compared to the other two electrodes fabricated similarly with only difference of fabrication temperature (i.e., 500 and 550 °C).
关键词： photoelectrodes,photoelectrochemical water splitting,aerosol assisted chemical vapor deposition,CaTiO3–TiO2 composite
更新于2025-09-10 09:29:36