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

Abstract

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 mmol <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow></mml:mrow> <mml:mrow><mml:mi>H</mml:mi> <mml:msub><mml:mrow></mml:mrow> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> </mml:math> 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow></mml:mrow> <mml:mrow><mml:mi>H</mml:mi> <mml:msub><mml:mrow></mml:mrow> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> </mml:math> 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 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.