Selective etching of metastable phase induced an efficient CuIn0.7Ga0.3S2 nano-photocathode for solar water splitting†
Abstract
A p–n tandem photoelectrochemical water splitting cell is considered as a promising low-cost technique to convert solar energy into hydrogen. A p type CuIn0.7Ga0.3S2 is an attractive photocathode with a high photocurrent onset potential. However, it is still a key challenge to explore an efficient CuIn0.7Ga0.3S2 photocathode. Two kinds of impurities, CuxS and a metastable CuAu ordering phase, usually exist in CuIn1−xGaxS2, which are both considered to be harmful to the performance of CuIn1−xGaxS2-based solar conversion devices. However, in this study, the photocurrent of a CuIn0.7Ga0.3S2 nano-photocathode is significantly enhanced by selective electrochemical etching of a CuAu ordering phase, but not increased after etching of CuxS. Moreover, having been further coated with CdS and Pt co-catalyst, a Pt/CdS/CuIn0.7Ga0.3S2 nano-photocathode exhibits a high solar photocurrent density of 6.0 mA cm−2 at 0 VRHE under AM 1.5G simulated sunlight (100 mW cm−2) irradiation, which is comparable with the highest recorded photocurrent on a Pt/CdS/CuIn1−xGaxS2 microcrystal photocathode. This strategy will be helpful to explore other efficient Cu-chalcopyrite solar conversion devices.
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