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

Abstract

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 mmol H 2 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 mmol H 2 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.