Cuprous Oxide Photocathode Research Articles

Experimental investigation of a new photoelectrochemical cell design featuring a unique photocathode configuration for solar hydrogen production

The electrodeposition process and the subsequent assessment of a novel cuprous oxide photocathode are conducted for solar light-based hydrogen production. The mesh dome photocathode helps facilitate the optimal light harvesting, enabling the efficient collection of the maximum accessible light from the solar simulator. This particular design also ensures that light reaches the remote surfaces of the photocathode through penetrating the mesh structure. The electrodeposition method is then employed to coat cuprous oxide onto the stainless-steel electrode. The subsequent examination of this photocathode occurs within an alkaline solution of potassium dioxide to assess its performance in hydrogen production. The study investigates the impact of the new design of the mesh photocathode on hydrogen generation rates, as well as related efficiencies of energy and exergy, under varying light angles during daylight hours. The present experimental findings reveal that the maximum rates of hydrogen production, achieved at a 45° tilt light and 0.25 M KOH, are 15.38 μg/s and it is 15.83 μg/s for vertical light positions. Furthermore, the highest recorded system exergy and energy efficiencies under vertical light conditions are 2.19% and 3.20%, respectively, compared to 2.14% and 3.12% at applying tilted light. The new photocathode design contributes to a notable 80.3% improvement in hydrogen generation rate at tilted light angles in comparison to vertical light conditions.

Hydration deactivation mechanism of the 〈100〉 oriented cuprous oxide photocathodes in solar water splitting and the regenerated three-dimensional structure.

Photocorrosion is the most ticklish problem of cuprous oxide (Cu2O), and it is widely assumed that the deactivation of Cu2O photocathodes in solar water splitting is caused by spontaneous oxidation-reduction (REDOX) reactions. However, this work shows that 〈100〉-oriented Cu2O photocathodes undergo a non-REDOX hydration deactivation mechanism. Briefly, water molecules are embedded in the Cu2O crystals at low potential under illumination and produce amorphous CuOH, which can be dehydrated at high potential to heal the Cu-O-Cu bonds and regenerate foamed Cu2O films with a three-dimensional skeleton structure. This study provides a new insight towards the protection and application of Cu2O photocathodes.

Hydrogen-substituted graphdiyne encapsulated cuprous oxide photocathode for efficient and stable photoelectrochemical water reduction

Photoelectrochemical (PEC) water splitting is an appealing approach for “green” hydrogen generation. The natural p-type semiconductor of Cu2O is one of the most promising photocathode candidates for direct hydrogen generation. However, the Cu2O-based photocathodes still suffer severe self-photo-corrosion and fast surface electron-hole recombination issues. Herein, we propose a facile in-situ encapsulation strategy to protect Cu2O with hydrogen-substituted graphdiyne (HsGDY) and promote water reduction performance. The HsGDY encapsulated Cu2O nanowires (HsGDY@Cu2O NWs) photocathode demonstrates a high photocurrent density of −12.88 mA cm−2 at 0 V versus the reversible hydrogen electrode under 1 sun illumination, approaching to the theoretical value of Cu2O. The HsGDY@Cu2O NWs photocathode as well as presents excellent stability and contributes an impressive hydrogen generation rate of 218.2 ± 11.3 μmol h−1cm−2, which value has been further magnified to 861.1 ± 24.8 μmol h−1cm−2 under illumination of concentrated solar light. The in-situ encapsulation strategy opens an avenue for rational design photocathodes for efficient and stable PEC water reduction.

Turning solar energy into Hydrogen with cuprous oxide

Cuprous oxide photocathode application in solar water splitting reviewed.

Nanopixelated Cuprous Oxide Photocathodes for Durable Photoelectrochemical Water Splitting

Nanopixelated Cuprous Oxide Photocathodes for Durable Photoelectrochemical Water Splitting

Cuprous oxide photocathodes for solar water splitting

Solar water splitting is a promising technique for harvesting solar energy and converting abundant sunlight into storable hydrogen fuel. The cuprous oxide photocathode, one of the best-performing oxide photocathodes, possesses a theoretical photocurrent density of up to 14.7 mA cm−2 and a photovoltage as large as 1.6 V, making it possible to convert solar energy into hydrogen energy in a low-cost way. Herein, a comprehensive review of improving the solar water splitting performance of the cuprous oxide photocathode is presented with a focus on the crucial issues of increasing photocurrent density, photovoltage, and durability from the aspects of solving the incompatibility between the electron diffusion length and optical absorption distances, improving interfacial band alignment, revealing the impact of deficiencies, and introducing protective overlayers. We also outline the development of unassisted solar water splitting tandem devices with the cuprous oxide photocathode as a component, emphasizing the critical strategies to enhance the transmittance of the cuprous oxide photocathode, laying a solid foundation to further boost solar to hydrogen conversion efficiency. Finally, a perspective regarding the future directions for further optimizing the solar water splitting performance of the cuprous oxide photocathode and boosting solar to hydrogen conversion efficiency of the unbiased tandem device is also presented.

Titanium Nitride Protected Cuprous Oxide Photocathode for Stable and Efficient Water Reduction

Titanium Nitride Protected Cuprous Oxide Photocathode for Stable and Efficient Water Reduction

Photoelectrochemical Nitrogen Reduction to Ammonia on Cupric and Cuprous Oxide Photocathodes

Photoelectrochemical N2 reduction enables the production of NH3 under ambient conditions using water as the hydrogen source. Furthermore, by utilizing solar energy, photoelectrochemical N2 reductio...

Highly Stable Nanocrystal Engineered Palladium Decorated Cuprous Oxide Photocathode for Hydrogen Generation

AbstractPhotocorrosion stability and the discrepancy between optical absorption and carrier diffusion length of cuprous oxide (Cu2O) thin films are the main limiting factors for hydrogen evolution and practical applications of Cu2O photocathodes. In this paper, by nanocrystal engineering the Cu2O optical absorbing thin film, the photocorrosion stability can be significantly improved. Furthermore, palladium (Pd) nanostructures are used to both act as a cocatalysis and address the discrepancy between optical absorption and carrier diffusion length of cuprous oxide and improve the photocatalytic activity of Cu2O photocathodes. By tuning the crystal quality of thin Cu2O film and Pd nanostructures through controlling the sputtering power of Cu2O and in situ plasma of substrate, the impact of the degree of crystallinity of thin Cu2O film and Pd nanostructures on photocorrosion stability and photocatalytic activity of prepared photocathodes are investigated in detail. Systematic characterization of prepared samples by using X‐ray diffraction, high‐resolution transmission electron microscopy, and scanning electron microscope analysis indicates that improving the crystallinity of deposited Cu2O thin film and Pd nanostructures can significantly improve the photocorrosion stability and performance of Cu2O based photocathodes.

Cuprous Oxide Photocathode with Carbon-Based Protective and Electrocatalytic Layers for Efficient Water Splitting

Enormous efforts have been made to search suitable photocathode materials for photoelectrochemical (PEC) system, because it is a promising way to directly convert solar energy to H2, to meet the urgent demand for global energy. Among common photocathode materials, earth abundant p-type Cu2O is one of the most promising candidate due to its bandgap (2 eV), which facilitates visible light absorption, and its suitable conduction band (0.7 eV) which is negative of hydrogen evolution potential. But its poor stability in aqueous solution severely restricts its application in PEC system. To solve this problem, we adopt a simple and convenient method to form the ultrathin carbon film which has the outstanding electrical conductivity to transfer photogenerated electron from semiconductor into electrolyte solution to protect Cu2O from self-photocorrosion. It was found that carbon based catalyst with ultra-high hydrogen evolution reaction catalytic activity serves as an important role to enhance photocurrent density. This work provided a low cost and simple synthetic method for improving the stability of Cu2O planar film and efficiency of water splitting. This available strategy could expand to design many other materials which endure stability problem in PEC system, and the carbon based catalyst/carbon film/Cu2O multilayer structure might be the model system for basic research of designing other high-performance photocathode materials.

Photoelectrochemical deposition of CoP on cuprous oxide photocathodes for solar hydrogen production

Photoelectrochemical (PEC) water splitting is an attractive and sustainable energy conversion method. In this work, cobalt phosphide (CoP) is photoelectrochemically deposited on a p-type cuprous oxide (p-Cu2O) photocathode for solar hydrogen production. Under visible light irradiation, the PEC assembly is active for hydrogen evolution, generating a current density of up to −5.3mAcm−2 and −4.2mAcm−2 in acidic and basic conditions at 0V vs. the reversible hydrogen electrode (RHE).

Tin oxide as stable protective layer for composite cuprous oxide water-splitting photocathodes

For a sustainable future, efficient solar energy harvesting and storage is required. Solar hydrogen production from photoelectrochemical water splitting is a promising technology and, in particular, cuprous oxide photocathodes are interesting photoelectrodes due to their high efficiency and low cost. However, chemical instability inhibits practical application of such devices. This work reports a novel strategy for protecting cuprous oxide from photocorrosion, wherein a thin SnO2 overlayer enables increased stability over previous reports utilizing TiO2 protective layers. Performance and stability are influenced by the film thickness, post-deposition steam treatment, and the nature of the heterojunction interface. Stability over 57h of sustained photoelectrochemical water reduction, maintaining 90% of initial photocurrent, is achieved.

Automatic illumination compensation device based on a photoelectrochemical biofuel cell driven by visible light.

Inverted illumination compensation is important in energy-saving projects, artificial photosynthesis and some forms of agriculture, such as hydroponics. However, only a few illumination adjustments based on self-powered biodetectors that quantitatively detect the intensity of visible light have been reported. We constructed an automatic illumination compensation device based on a photoelectrochemical biofuel cell (PBFC) driven by visible light. The PBFC consisted of a glucose dehydrogenase modified bioanode and a p-type semiconductor cuprous oxide photocathode. The PBFC had a high power output of 161.4 μW cm(-2) and an open circuit potential that responded rapidly to visible light. It adjusted the amount of illumination inversely irrespective of how the external illumination was changed. This rational design of utilizing PBFCs provides new insights into automatic light adjustable devices and may be of benefit to intelligent applications.

Transparent Cuprous Oxide Photocathode Enabling a Stacked Tandem Cell for Unbiased Water Splitting

Photoelectrochemical water splitting represents an attractive method of capturing and storing the immense energy of sunlight in the form of hydrogen, a clean chemical fuel. Given the large energetic demand of water electrolysis, and the defined spectrum of photons available from incident sunlight, a two absorber tandem device is required to achieve high efficiencies. The two absorbers should be of different and complementary bandgaps, connected in series to achieve the necessary voltage, and arranged in an optical stack configuration to maximize the utilization of sunlight. This latter requirement demands a top device that is responsive to high‐energy photons but also transparent to lower‐energy photons, which pass through to illuminate the bottom absorber. Here, cuprous oxide (Cu2O) is employed as a top absorber component, and the factors influencing the balance between transparency and efficiency toward operation in a tandem configuration are studied. Photocathodes based on Cu2O electrodeposited onto conducting glass substrates treated with thin, discontinuous layers of gold achieve reasonable sub‐bandgap transmittance while retaining performances comparable to their opaque counterparts. This new high‐performance transparent photocathode is demonstrated in tandem with a hybrid perovskite photovoltaic cell, resulting in a full device capable of standalone sunlight‐driven water splitting.

Photoelectrochemical hydrogen production in alkaline solutions using Cu2O coated with earth-abundant hydrogen evolution catalysts.

The splitting of water into hydrogen and oxygen molecules using sunlight is an attractive method for solar energy storage. Until now, photoelectrochemical hydrogen evolution is mostly studied in acidic solutions, in which the hydrogen evolution is more facile than in alkaline solutions. Herein, we report photoelectrochemical hydrogen production in alkaline solutions, which are more favorable than acidic solutions for the complementary oxygen evolution half-reaction. We show for the first time that amorphous molybdenum sulfide is a highly active hydrogen evolution catalyst in basic medium. The amorphous molybdenum sulfide catalyst and a Ni-Mo catalyst are then deposited on surface-protected cuprous oxide photocathodes to catalyze sunlight-driven hydrogen production in 1 M KOH. The photocathodes give photocurrents of -6.3 mA cm(-2) at the reversible hydrogen evolution potential, the highest yet reported for a metal oxide photocathode using an earth-abundant hydrogen evolution reaction catalyst.

Photoelectrochemical Hydrogen Production in Alkaline Solutions Using Cu2O Coated with Earth‐Abundant Hydrogen Evolution Catalysts

AbstractThe splitting of water into hydrogen and oxygen molecules using sunlight is an attractive method for solar energy storage. Until now, photoelectrochemical hydrogen evolution is mostly studied in acidic solutions, in which the hydrogen evolution is more facile than in alkaline solutions. Herein, we report photoelectrochemical hydrogen production in alkaline solutions, which are more favorable than acidic solutions for the complementary oxygen evolution half‐reaction. We show for the first time that amorphous molybdenum sulfide is a highly active hydrogen evolution catalyst in basic medium. The amorphous molybdenum sulfide catalyst and a Ni–Mo catalyst are then deposited on surface‐protected cuprous oxide photocathodes to catalyze sunlight‐driven hydrogen production in 1 M KOH. The photocathodes give photocurrents of −6.3 mA cm−2 at the reversible hydrogen evolution potential, the highest yet reported for a metal oxide photocathode using an earth‐abundant hydrogen evolution reaction catalyst.

Ruthenium Oxide Hydrogen Evolution Catalysis on Composite Cuprous Oxide Water‐Splitting Photocathodes

Photocathodes based on cuprous oxide (Cu2O) are promising materials for large scale and widespread solar fuel generation due to the abundance of copper, suitable bandgap, and favorable band alignments for reducing water and carbon dioxide. A protective overlayer is required to stabilize the Cu2O in aqueous media under illumination, and the interface between this overlayer and the catalyst nanoparticles was previously identified as a key source of instability. Here, the properties of the protective titanium dioxide overlayer of composite cuprous oxide photocathodes are further investigated, as well as an oxide‐based hydrogen evolution catalyst, ruthenium oxide (RuO2). The RuO2‐catalyzed photoelectrodes exhibit much improved stability versus platinum nanoparticles, with 94% stability after 8 h of light‐chopping chronoamperometry. Faradaic efficiencies of ∼100% are obtained as determined by measurement of the evolved hydrogen gas. The sustained photocurrents of close to 5 mA cm−2 obtained with this electrode during the chronoamperometry measurement (at 0 V vs. the reversible hydrogen electrode, pH 5, and simulated 1 sun illumination) would correspond to greater than 6% solar‐to‐hydrogen conversion efficiency in a tandem photoelectrochemical cell, where the bias is provided by a photovoltaic device such as a dye‐sensitized solar cell.

Dye sensitization of low-bandgap semiconductor electrodes: cuprous oxide photocathode sensitized with methyl violet

When illuminated, dye-coated semiconductor electrodes inject electrons (holes) into the conduction (valence) band so that the photoresponse of high-bandgap semiconductors is extended to the visible region. It is found that when low-bandgap semiconductor electrodes are coated with dyes, the photocurrent in the bandgap region wavelengths is also enhanced. The effect is explained as originating from suppression of the recombination of carriers generated by photons captured directly by the semiconductor surface.

Stability of cuprous thiocyanate coated cuprous oxide photocathode in aqueous thiocyanate

It is found that a thin coating of cuprous thiocyanate suppresses photocorrosion of cuprous oxide in aqueous KCNS. The method of deposition of cuprous thiocyanate on cuprous oxide surface and the performance of a photoelectrochemical cell based on this electrode are described.

Stabilization of cuprous oxide photocathode in aqueous thiocyanate solution by aliphatic alcohols

Long-chain normal aliphatic alcohols are found to suppress photocorrosion and increase the efficiency of a cuprous oxide photoelectrochemical cell with aqueous thiocyanate solution as the electrolyte. It is suggested that alcohols inhibit corrosion by surface adsorption.