Heterostructure of Si and CoSe₂: A promising photocathode based on a non-noble metal catalyst for photoelectrochemical hydrogen evolution

Development of a solar water splitting device requires design of a low-cost, efficient, and non-noble metal compound as alternative to noble metals. For the first time, we showed that CoSe₂ can function as co-catalyst in phototoelectrochemical hydrogen production. We designed a heterostructure of p-Si and marcasite-type CoSe₂ for solar-driven hydrogen production. CoSe₂ successively coupled with p-Si can act as a superior photocathode in the solar-driven water splitting reaction. Photocurrents up to 9 mA cm^-2 were achieved at 0 V vs. reversible hydrogen electrode. Electrochemical impedance spectroscopy showed that the high photocurrents can be attributed to low charge transfer resistance between the Si and CoSe₂ interfaces and that between the CoSe₂ and electrolyte interfaces. Our results suggest that this CoSe₂ is a promising alternative co-catalyst for hydrogen evolution.