Cu(In,Ga)S2 nanowire arrays: Self-templated synthesis and application for photoelectrochemical water splitting

Highlights: • CIGS NWAs was synthesized for the first time via a solvothermal method using Cu₂S templates. • A novel cation-exchange growth mechanism was proposed. • The enhanced PEC performance and light absorption property of CIGS NWAs were investigated. Polycrystalline Cu(In,Ga)S₂ (CIGS) nanowire arrays (NWAs) are synthesized for the first time via a solvothermal method using Cu₂S NWAs as self-sacrificial templates. The average diameter and length of the as-synthesized CIGS nanowires are 350 nm and 5 μm, respectively. Based on the experimental results, a novel cation-exchange growth mechanism is proposed. The In³⁺ and Ga³⁺ ions diffuse inward while the Cu⁺ ions outward during the solvothermal reaction, resulting in the formation of CIGS with keeping the original nanowire morphology. We have also investigated the photoelectrochemical performance of CIGS NWAs compared with the pristine Cu₂S templates. The photocurrent density and optimal incident photon to current efficiency of CIGS NWAs are 0.39 mA cm⁻² and 6% at 450 nm, respectively, which are much higher than those of the Cu₂S templates. The reported method will lay a foundation for the synthesis of other multi-compound (ternary and above) metal chalcogenides for PEC applications.