Hydrogen evolution from water using AgxCu1−xGaSe2 photocathodes under visible light

Abstract

Photoelectrochemical (PEC) water splitting using CuGaSe₂ (CGSe) thin film photocathodes modified by partial substitution of Cu with Ag was investigated. The Ag_xCu_1−xGaSe₂ (ACGSe) thin films were deposited onto Mo-coated soda-lime glass substrates by means of co-evaporation using a molecular beam epitaxy (MBE) system. The valence band maximum (VBM) potential of ACGSe is deeper than that of CGSe, and its grain size is greatly increased compared to that of CGSe. A Pt and CdS modified ACGSe electrode (Pt/CdS/ACGSe) with a Ag/(Cu + Ag) ratio of about 5% showed a cathodic photocurrent of 8.1 mA cm⁻² at 0 V_RHE and an onset potential of 0.70 V_RHE (defined as a cathodic photocurrent of 0.05 mA cm⁻²) under simulated sunlight in a 0.1 M Na₂SO₄ solution (pH 9.5). Moreover, Pt/CdS/ACGSe exhibited a stable cathodic photocurrent for over 55 h, with no clear decrease.