Band gap-tunable (CuIn)xZn2(1−x)S2 solid solutions: preparation and efficient photocatalytic hydrogen production from water under visible light without noble metals

Abstract

A series of (CuIn)_xZn_2(1−x)S₂ solid solutions has been successfully synthesized by a solvothermal approach, and the obtained solid solutions, with a size of about 10 nm, exhibit significant absorption in the visible light region and their band gap can be correspondingly tuned from 2.59 eV to 1.64 eV with an increase of the x value from 0.05 to 0.5, implying that they can be used as visible-light driven photocatalysts. Furthermore, the obtained (CuIn)_xZn_2(1−x)S₂ solid solutions display highly efficient photocatalytic activities for H₂ evolution from aqueous solutions containing sacrificial reagents (SO₃²⁻ and S²⁻) under visible light (λ > 420 nm) even without noble metal co-catalysts, e.g. (CuIn)_0.2Zn_1.6S₂, with a band gap of 2.10 eV, exhibits the highest photocatalytic activity of 0.984 mmol g⁻¹ h⁻¹ even without a Pt co-catalyst. Further studies reveal that the photocatalytic H₂ evolution of solid solutions depends on their composition as well as the photophysical properties, such as the ability to absorb visible light and the generation and separation of photo-induced electrons and holes.