Heterostructure of Si and CoSe 2 : 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 CoSe 2 can function as co‐catalyst in phototoelectrochemical hydrogen production. We designed a heterostructure of p‐Si and marcasite‐type CoSe 2 for solar‐driven hydrogen production. CoSe 2 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 CoSe 2 interfaces and that between the CoSe 2 and electrolyte interfaces. Our results suggest that this CoSe 2 is a promising alternative co‐catalyst for hydrogen evolution.