A novel noble-metal-free binary and ternary In2S3 photocatalyst with WC and "W-Mo auxiliary pairs" for highly-efficient visible-light hydrogen evolution

Highlights: • A novel noble-metal-free ternary In₂S₃ photocatalyst with W-Mo auxiliary pairs was synthesized by a solvothermal method. • WC and MoS₂ can form W-Mo auxiliary pairs that will be utilized to synergistically maximize the photocatalytic activity. • The photocatalytic activity of optimal In₂S₃-WC and In₂S₃-WC-MoS₂ is much higher than pure In₂S₃ and In₂S₃-1% Pt. • The very possible photocatalytic hydrogen production mechanism of superior photocatalyst was discussed. -- Abstract: Herein, noble-metal-free In₂S₃-WC and In₂S₃-based photocatalysts with dual cocatalysts of flower-like MoS₂ and bulk WC were synthesized through a facile solvothermal reaction. Electrochemical results indicated WC increased the interface conductance of photocatalyst and boosted the transference of photogenerated carriers. The optimal In₂S₃-WC show a hydrogen production rate of 128.11 μmol·h⁻¹·g⁻¹, which is around 6 times higher than In₂S₃-1%Pt (20.73 μmol·h⁻¹·g⁻¹). The above results demonstrate commercial WC has a crucial impact of replacing precious metal and separating carriers. Morphology characterization exhibited hydrangea In₂S₃ and flower-like MoS₂ were attached to bulk WC. Gratifyingly, photocurrent, impedance and photoluminescence results demonstrated MoS₂ further effectively separated the photogenerated carriers. Remarkably, the higher hydrogen generation rate of 390.52 μmol·h⁻¹·g⁻¹ obtained by the optimal ternary In₂S₃-WC-MoS₂ composite was around 3 and 18 times higher than the optimal In₂S₃-WC and In₂S₃-1% Pt. The photocatalytic results demonstrated that ^W-Mo auxiliary pairs was a great efficient synergistic cocatalyst for In₂S₃ to increase active sites and improve e^--h⁺ pairs separation for H₂ generation. Furthermore, a probable reaction mechanism of the enhanced photocatalytic H₂ generation was also proposed. This presented research provides an effective concept to design novel and efficient noble-metal-free photocatalyst with ^W-Mo auxiliary pairs for prominent H₂ generation activity.