Light‐driven water splitting with metal oxide semiconductor materials to produce H2 constitutes one of the most promising energy conversion technologies built on solar power. BiVO4 stands out as one of the most attractive metal oxides with reported photocurrents close to its theoretical maximum of 7.5 mA cm−2 at 1 sun illumination. The present work addresses the state‐of‐the‐art strategies to enhance the performance of this material for water oxidation by heterostructuring with different underlayer (SnO2 and WO3) and overlayer (NiOOH/FeOOH, Co–Pi, Co–Fe Prussian Blue derivative) materials, with particular emphasis on the physico‐chemical mechanisms responsible for the reported enhancements. 相似文献
In this study, a potentially universal new strategy is reported for the large-scale, low-cost fabrication of visible-light-active highly ordered heteronanostructures based on the spontaneous photoelectric-field-enhancement effect inherent in pyramidal morphology. The hierarchical vertically oriented arrayed structures comprise an active molecular co-catalyst at the apex of a visible-light-active large band gap semiconductor for low-cost solar water splitting in a neutral aqueous medium without the use of a sacrificial agent.
Bismuth vanadate (BiVO4) is a promising photoanode material for photoelectrochemical (PEC) water splitting. However, owing to the short carrier diffusion length, the trade‐off between sufficient light absorption and efficient charge separation often leads to poor PEC performance. Herein, a new electrodeposition process is developed to prepare bismuth oxide precursor films, which can be converted to transparent BiVO4 films with well‐controlled oxygen vacancies via a mild thermal treatment process. The optimized BiVO4 film exhibits an excellent back illumination charge separation efficiency mainly due to the presence of enriched oxygen vacancies which act as shallow donors. By loading FeOOH/NiOOH as the cocatalysts, the BiVO4 dual photoanodes exhibit a remarkable and highly stable photocurrent density of 5.87 mA cm?2 at 1.23 V versus the reversible hydrogen electrode under AM 1.5 G illumination. An artificial leaf composed of the BiVO4/FeOOH/NiOOH dual photoanodes and a single sealed perovskite solar cell delivers a solar‐to‐hydrogen conversion efficiency as high as 6.5% for unbiased water splitting. 相似文献
Micrometer‐sized light‐absorbing semiconductor particles (usually prepared by high temperature synthetic techniques) hold the desirable merits of high crystallinity, low concentrations of bulk defects, and a decreased grain boundary density to reduce bulk recombination of photocarriers. However, solar‐water‐splitting electrodes assembled using them as precursors always produce very low photocurrents. This could be due to the lack of an effective fabrication and/or modification protocol applicable to assemble these micrometer‐sized semiconductor particles into suitable electrode configurations. A fast and simple fabrication scheme of drop‐casting followed by the necking treatment is developed to enable the micrometer‐sized precursor particles derived photoelectrodes to deliver appreciable photocurrent densities (>1 mA cm−2). By applying this fabrication scheme, photoelectrodes of solid‐state reaction derived Mo doped BiVO4 (≈4 μm, modified with oxygen evolution catalysts) and commercial WO3 (size ranging from 100 nm to >10 μm) have yielded photocurrent densities higher than 1 mA cm−2, while the photoelectrode composed of commercial CdSe (≈10 μm) is able to produce a photocurrent density higher than 5 mA cm−2 (in a Na2S aqueous solution). This strategy provides a new possible way, in addition to the predominant route of nanostructuring, to construct efficient solar‐water‐splitting electrodes. 相似文献
Carbon nanotube (CNT)/semiconducting oxide hybrids are an ideal architecture for light‐harvesting devices, in which the CNTs are expected to not only act as a scaffold but also provide fast transport paths for photogenerated charges in the oxide. However, the current potential of CNTs for charge transport is largely suppressed due to the nanotubes not being interconnected but isolated by the low conductive oxide coatings. Herein, a flexible and conductive CNT/TiO2 core/shell heterostructure film is reported, with aligned and interconnected CNTs wrapped in a continuous TiO2 coating. Without using additional transparent conducting oxide (TCO) substrates, this unique feature of the film boosts the incident photon‐to‐electron conversion efficiency to 32%, outperforming TiO2 nanoparticle electrodes fabricated on TCO substrates. Moreover, the film shows high structural stability and can generate a stable photocurrent even after being bent hundreds of times. 相似文献
Despite a suitable bandgap of bismuth vanadate (BiVO4) for visible light absorption, most of the photogenerated holes in BiVO4 photoanodes are vanished before reaching the surfaces for oxygen evolution reaction due to the poor charge separation efficiency in the bulk. Herein, a new sulfur oxidation strategy is developed to prepare planar BiVO4 photoanodes with in situ formed oxygen vacancies, which increases the majority charge carrier density and photovoltage, leading to a record charge separation efficiency of 98.2% among the reported BiVO4 photoanodes. Upon loading NiFeOx as an oxygen evolution cocatalyst, a stable photocurrent density of 5.54 mA cm−2 is achieved at 1.23 V versus the reversible hydrogen electrode (RHE) under AM 1.5 G illumination. Remarkably, a dual-photoanode configuration further enhances the photocurrent density up to 6.24 mA cm−2, achieving an excellent applied bias photon-to-current efficiency of 2.76%. This work demonstrates a simple thermal treatment approach to generate oxygen vacancies for the design of efficient planar photoanodes for solar hydrogen production. 相似文献
Boosting charge separation and transfer of photoanodes is crucial for providing high viability of photoelectrochemical hydrogen (H2) generation. Here, a structural engineering strategy is designed and synthesized for uniformly coating an ultrathin CoFe bimetal-organic framework (CoFe MOF) layer over a BiVO4 photoanode for boosted charge separation and transfer. The photocurrent density of the optimized BiVO4/CoFe MOF(NA) photoanode reaches a value of 3.92 mA cm−2 at 1.23 V versus reversible hydrogen electrode (RHE), up to 6.03 times that of pristine BiVO4, due to the greatly increased efficiency of charge transfer and separation. In addition, this photoanode records one onset potential that is considerably shifted negatively when compared to BiVO4. Transient absorption spectroscopy reveals that the CoFe MOF(NA) prolongs charge recombination lifetime by blocking the hole-transfer pathway from the BiVO4 to its surface trap states. This work sheds light on boosting charge separation and transfer through structural engineering to enhance the photocurrent of photoanodes for solar H2 production. 相似文献
An improved variation of highly active/durable O2‐evolving LaTiO2N powder‐based photoelectrode has been fabricated by pre‐cleaning the powder with mild polysulfonic acid and by homogeneous deposition of CoOx co‐catalyst aided by microwave annealing. The treatment in aqueous solution of poly(4‐styrene sulfonic acid) results in removal of surface LaTiO2N layers, forming fine pores in the crystallites. The CoOx co‐catalyst by microwave deposition in Co(NH3)6Cl3/ethylene glycol homogeneously covers the particle surface. The LaTiO2N powder is fabricated into particle‐transferred electrodes on Ti thin film supported on solid substrate. The modified LaTiO2N grains on the electrode serve as a highly active O2‐evolving photoanode achieving 8.9 mA cm?2 of the photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) in 0.1 m NaOH (pH 13) under solar‐simulator irradiation Airmass 1.5 Global (AM 1.5G). The activity has been much improved, compared with conventional LaTiO2N treated in mineral acid or with CoOx deposited by impregnation. The new electrode also exhibits better durability in fixed‐potential chronoamperometric tests under AM 1.5G irradiation. 相似文献
The activity of polycrystalline thin film photoelectrodes is impacted by local variations of the material properties due to the exposure of different crystal facets and the presence of grain/domain boundaries. Here a multi‐modal approach is applied to correlate nanoscale heterogeneities in chemical composition and electronic structure with nanoscale morphology in polycrystalline Mo‐BiVO4. By using scanning transmission X‐ray microscopy, the characteristic structure of polycrystalline film is used to disentangle the different X‐ray absorption spectra corresponding to grain centers and grain boundaries. Comparing both spectra reveals phase segregation of V2O5 at grain boundaries of Mo‐BiVO4 thin films, which is further supported by X‐ray photoelectron spectroscopy and many‐body density functional theory calculations. Theoretical calculations also enable to predict the X‐ray absorption spectral fingerprint of polarons in Mo‐BiVO4. After photo‐electrochemical operation, the degraded Mo‐BiVO4 films show similar grain center and grain boundary spectra indicating V2O5 dissolution in the course of the reaction. Overall, these findings provide valuable insights into the degradation mechanism and the impact of material heterogeneities on the material performance and stability of polycrystalline photoelectrodes. 相似文献
The integration of photoelectrochemical photoanodes and solar cells to build an unbiased solar-to-hydrogen (STH) conversion system provides a promising way to solve the energy crisis. The key point is to develop highly transparent photoanodes, while its bulk separation efficiency (ηsep.) and surface injection efficiency are as high as possible. To resolve this contradiction, first a novel CdIn2S4/In2S3 bulk heterojunctions in the interior of nanosheets is designed as a photoanode with high transparency and an ultrahigh ηsep. up to 90%. Furthermore, decorating the ultrathin amorphous SnO2 layer by atomic layer deposition, the surface oxygen-evolution kinetics of the photoanode are increased significantly. As a result, the onset potential of the photoanode shifts negatively to 0.02 V vs RHE, and the photocurrent density boosts to 2.98 mA cm−2 at 1.23 V vs RHE, which is ten times higher than that of pristine CdIn2S4. Such a high-performance photoanode enables the integrated metal sulfide photoanode–perovskite solar cell system to deliver a STH conversion efficiency of 3.3%. 相似文献
Polymeric carbon nitride is a promising photoanode material for water-splitting and organic transformation-based photochemical cells. Despite achieving significant progress in performance, these materials still exhibit low photoactivity compared to inorganic photoanodic materials because of a moderate visible light response, poor charge separation, and slow oxidation kinetics. Here, the synthesis of a sodium- and boron-doped carbon nitride layer with excellent activity as a photoanode in a water-splitting photoelectrochemical cell is reported. The new synthesis consists of the direct growth of carbon nitride (CN) monomers from a hot precursor solution, enabling control over the monomer-to-dopant ratio, thus determining the final CN properties. The introduction of Na and B as dopants results in a dense CN layer with a packed morphology, better charge separation thanks to the in situ formation of an electron density gradient, and an extended visible light response up to 550 nm. The optimized photoanode exhibits state-of-the-art performance: photocurrent densities with and without a hole scavenger of about 1.5 and 0.9 mA cm−2 at 1.23 V versus reversible hydrogen electrode (RHE), and maximal external quantum efficiencies of 56% and 24%, respectively, alongside an onset potential of 0.3 V. 相似文献
Photoelectrode materials are the heart of photoelectrochemical (PEC) cells, which hold great promise to address global energy and environmental issues by converting solar energy into electricity or chemical fuels. In recent decades, significant research efforts have been devoted to the design and construction of photoelectrodes for the efficient generation and utilization of charge carriers to boost PEC performance. Herein, insights from a literature study on the relationship between the architecture and charge dynamics of photoelectrodes are presented. After briefly introducing the fundamental theories of charge dynamics in nanostructured photoelectrodes, the development of photoelectrode design in 1D polycrystalline nanotube arrays, 1D single‐crystalline nanowire arrays, and hierarchical and mesoporous nanowire arrays is reviewed with a focus on the interplay between architecture and charge transport properties. For each design, commonly used synthetic approaches and the corresponding charge transport properties are discussed. Subsequently, the applications of these photoelectrodes in PEC systems are summarized. In conclusion, future challenges in the rational design of photoelectrode architecture are presented. The basic relationships between the architectures and charge dynamics of photoelectrode materials discussed here are expected to provide pertinent guidance and a reference for future advanced material design targeting improved light energy conversion systems. 相似文献
下载免费PDF全文