Post-Addition of Metal Species over CdIn2S4 Micro-Pyramids/Nanosheets for Photocatalytic Hydrogen Production and Benzylamine Valorization

Abstract

Photocatalysis is a sustainable technology that can be used to produce fuels and chemicals. Cadmium indium sulfide (CdIn₂S₄) is a promising photocatalyst due to its high efficiency and ability to absorb sunlight. CdIn₂S₄ is one of the few semiconductors that can absorb up to 620 nm which represents 21% of the photons in solar illumination. Metal species can enhance the photocatalytic performance of CdIn₂S₄ through increasing charge separation and acting as catalytic sites for redox reactions. Herein, CdIn₂S₄ micropyramids/nanosheets were synthesized via a solvothermal synthesis and plasma-treated. Different metal species (atomic/small nanoclusters) were post-added to them via the deposition–precipitation route. The plasma-treated CdIn₂S₄ achieved an enhanced H₂ production rate of 985 μmol  g⁻¹ h⁻¹ in the presence of benzylamine under visible light irradiation (λ > 400 nm) compared to untreated CdIn₂S₄ (667 μmol  g⁻¹ h⁻¹). The introduction of Au and Ru species further enhanced the H₂ production rate to ~8.1 times (7968 μmol  g⁻¹ h⁻¹) and 6.7 times (6632 μmol  g⁻¹ h⁻¹), respectively, compared to the plasma-treated CdIn₂S₄. The plasma-treated Au-CdIn₂S₄ displayed photocatalytic oxidative coupling of benzylamine into N-benzylidenebenzylamine (a value-added product) with high selectivity >92% at a rate of 1102 μmol  g⁻¹ h⁻¹ under visible light irradiation (λ > 400 nm).