Plasmonic-induced overgrowth of amorphous molybdenum sulfide on nanoporous gold: An ambient synthesis method of hybrid nanoparticles with enhanced electrocatalytic activity

Hybrid materials of earth abundant transition metal dichalcogenides and noble metal nanoparticles, such as molybdenum sulfide (MoS_x) and gold nanoparticles, exhibit synergistic effects that can enhance electrocatalytic reactions. However, most current hybrid MoS_x-gold synthesis requires an energy intensive heat source of >500 °C or chemical plating to achieve deposition of MoS_x on the gold surface. Herein, we demonstrate the direct overgrowth of MoS_x over colloidal nanoporous gold (NPG), conducted feasibly under ambient conditions, to form hybrid particles with enhanced electrocatalytic performance toward hydrogen evolution reaction. Our strategy exploits the localized surface plasmon resonance-mediated photothermal heating of NPG to achieve >230 °C surface temperature, which induces the decomposition of the (NH₄)₂MoS₄ precursor and direct overgrowth of MoS_x over NPG. By tuning the concentration ratio between the precursor and NPG, the amount of MoS_x particles deposited can be systematically controlled from 0.5% to 2% of the Mo/(Au + Mo) ratio. Importantly, we find that the hybrid particles exhibit higher bridging and an apical S to terminal S atomic ratio than pure molybdenum sulfide, which gives rise to their enhanced electrocatalytic performance for hydrogen evolution reaction. We demonstrate that hybrid MoS_x-NPG exhibits >30 mV lower onset potential and a 1.7-fold lower Tafel slope as compared to pure MoS_x. Our methodology provides an energy- and cost-efficient synthesis pathway, which can be extended to the synthesis of various functional hybrid structures with unique properties for catalysis and sensing applications.