ZnSe Nanorods as Visible‐Light Absorbers for Photocatalytic and Photoelectrochemical H2 Evolution in Water

A precious‐metal‐ and Cd‐free photocatalyst system for efficient H2 evolution from aqueous protons with a performance comparable to Cd‐based quantum dots is presented. Rod‐shaped ZnSe nanocrystals (nanorods, NRs) with a Ni(BF4)2 co‐catalyst suspended in aqueous ascorbic acid evolve H2 with an activity up to 54±2 mmolH2 gZnSe−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 gZnSe−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 CuCrO2 photocathode, which does not rely on a sacrificial electron donor. Immobilized ZnSe NRs on CuCrO2 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 H2 generation. Cd‐free photocatalysis: Efficient visible‐light‐driven H2 generation was achieved using aqueous ZnSe nanorods as stable, Cd‐free light absorbers with benchmark activity of up to 150 mmol g−1 h−1 and 50 % quantum yield in suspension. A CuCrO2|ZnSe photocathode was constructed, enabling low‐cost, co‐catalyst‐free photoelectrochemical H2 production.