ZnSe Nanorods as Visible‐Light Absorbers for Photocatalytic and Photoelectrochemical H 2 Evolution in Water

A precious‐metal‐ and Cd‐free photocatalyst system for efficient H 2 evolution from aqueous protons with a performance comparable to Cd‐based quantum dots is presented. Rod‐shaped ZnSe nanocrystals (nanorods, NRs) with a Ni(BF 4 ) 2 co‐catalyst suspended in aqueous ascorbic acid evolve H 2 with an activity up to 54±2 mmolH2 g ZnSe −1  h −1 and a quantum yield of 50±4 % ( λ =400 nm) under visible light illumination (AM 1.5G, 100 mW cm −2 , λ >400 nm). Under simulated full‐spectrum solar irradiation (AM 1.5G, 100 mW cm −2 ), up to 149±22 mmolH2 g ZnSe −1  h −1 is generated. Significant photocorrosion was not noticeable within 40 h and activity was even observed without an added co‐catalyst. The ZnSe NRs can also be used to construct an inexpensive delafossite CuCrO 2 photocathode, which does not rely on a sacrificial electron donor. Immobilized ZnSe NRs on CuCrO 2 generate photocurrents of around −10 μA cm −2 in an aqueous electrolyte solution (pH 5.5) with a photocurrent onset potential of approximately +0.75 V vs. RHE. This work establishes ZnSe as a state‐of‐the‐art light absorber for photocatalytic and photoelectrochemical H 2 generation.