Hole‐Storage Enhanced a‐Si Photocathodes for Efficient Hydrogen Production

Abstract Ferrihydrite (Fh) has been demonstrated as an effective interfacial layer for photoanodes to achieve outstanding photoelectrochemical (PEC) performance for water oxidation reaction owing to its unique hole‐storage function. However, it is unknown whether such a hole‐storage layer can be used to construct highly efficient photocathodes for hydrogen evolution reaction (HER). In this work, we report Fh interfacial engineering of amorphous silicon photocathode (with nickel as HER cocatalyst) achieving a photocurrent density of 15.6 mA cm −2 at 0 V vs. the reversible hydrogen electrode and a half‐cell energy conversion efficiency of 4.08 % in alkaline solution, outperforming most of reported a‐Si based photocathodes including multi‐junction configurations integrated with noble metal cocatalysts in acid solution. Besides, the photocurrent density is maintained above 14 mA cm −2 for 175 min with 100 % Faradaic efficiency for HER in alkaline solution. Our results demonstrate a feasible approach to construct efficient photocathodes via the application of a hole‐storage layer.