Abstract
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.
Highlights
Hydrogen (H2 ) is a potential clean energy carrier that could replace fossil fuels and solve the associated environmental issues
These results indicate that the stability of the Pt/cadmium sulfide (CdS)/CuInS2 photoelectrodes significantly depended on the Pt loading
We investigated the effect of Pt loading on the PEC H2 -evolution activity and durability of CdS/CuInS2 photocathodes
Summary
Hydrogen (H2 ) is a potential clean energy carrier that could replace fossil fuels and solve the associated environmental issues. Since the first demonstration of PEC water splitting using a titanium dioxide (TiO2 ) photoelectrode was reported by Fujishima and Honda [3], semiconductor materials have been extensively studied as photoelectrodes to achieve efficient solar-to-H2 conversion [4,5,6,7,8,9,10]. The PEC performance of copper chalcopyrite photocathodes has been reported to improve when combined with n-type semiconductor buffer layers such as cadmium sulfide (CdS), indium sulfide (In2 S3 ), and zinc sulfide (ZnS). This is due to the formation of a p–n junction, which facilitates charge separation at the interface [17,18,19,20]. To achieve efficient and stable PEC H2 evolution, further improvements will be necessary to overcome the sluggish surface redox reactions and the instability of sulfide materials in aqueous solutions
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