Performance improvement of a p-Cu2O nanocrystal photocathode with an ultra-thin silver protective layer

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.

Key Strategies on Cu2O Photocathodes toward Practical Photoelectrochemical Water Splitting

Cuprous oxide (Cu2O) has been intensively in the limelight as a promising photocathode material for photoelectrochemical (PEC) water splitting. The state-of-the-art Cu2O photocathode consists of a back contact layer for transporting the holes, an overlayer for accelerating charge separation, a protection layer for prohibiting the photocorrosion, and a hydrogen evolution reaction (HER) catalyst for reducing the overpotential of HER, as well as a Cu2O layer for absorbing sunlight. In this review, the fundamentals and recent research progress on these components of efficient and durable Cu2O photocathodes are analyzed in detail. Furthermore, key strategies on the development of Cu2O photocathodes for the practical PEC water-splitting system are suggested. It provides the specific guidelines on the future research direction for the practical application of a PEC water-splitting system based on Cu2O photocathodes.

Noble Metal Modification of CdS-Covered CuInS2 Electrodes for Improved Photoelectrochemical Activity and Stability

In this paper, efficient and stable photoelectrochemical (PEC) hydrogen (H2) evolution using copper indium sulfide (CuInS2) thin film electrodes was studied. Modification with a cadmium sulfide (CdS) layer led to improved charge separation at the interface between CuInS2 and CdS; however, the photocorrosive nature of CdS induced poor stability of the photocathode. Further surface coating with an electrodeposited Pt layer over the CdS-covered CuInS2 photocathode prevented the CdS layer from making contact with the electrolyte solution, and enabled efficient PEC H2 evolution without appreciable degradation. This indicates that the Pt layer functioned not only as a reaction site for H2 evolution, but also as a protection layer. In addition, it was found that surface protection using a noble metal layer was also effective for stable PEC carbon dioxide (CO2) reduction when appropriate noble metal cocatalysts were selected. When Au or Ag was used, carbon monoxide was obtained as a product of PEC CO2 reduction.

High-efficiency photocatalytic water splitting by a N-doped porous g-C3N4 nanosheet polymer photocatalyst derived from urea and N,N-dimethylformamide

N-Doped porous g-C₃N₄ nanosheets for high-efficiency photocatalytic water splitting were prepared by mixing the precursor of N,N-dimethylformamide and urea through a simple one-step thermal copolymerization method.

Oxygen-defective ZnO porous nanosheets modified by carbon dots to improve their visible-light photocatalytic activity and gain mechanistic insight

A carbon dots/oxygen-defective ZnO (COZ) porous nanosheet composite photocatalyst was prepared via a one-step liquid-phase wet chemistry method for the highly efficient visible-light photocatalytic degradation of tetracycline (TC).