Electrocatalytic Performance of MoS₂ Quantum Dots toward the Hydrogen Evolution Reaction

Photocatalytic and photoelectrochemical water splitting have emerged as promising strategies for sustainable hydrogen production by converting solar energy into chemical energy. Among the various catalyst materials, transition metal dichalcogenides (TMDs), particularly molybdenum disulfide (MoS₂), have attracted considerable interest as cost-effective alternatives to noble metals because of their excellent catalytic activity, tunable electronic structure, and abundant active sites. In this work, hybrid-phase 1T/2H MoS₂ quantum dots (QDs) were successfully synthesized by a facile pulsed electrodeposition method and directly deposited onto indium tin oxide (ITO) substrates to fabricate efficient photocathodes for photoelectrochemical hydrogen evolution. Structural characterizations confirmed the coexistence of metallic 1T and semiconducting 2H phases, providing enhanced electrical conductivity, improved charge separation, and accelerated interfacial charge transfer. Under simulated AM 1.5G solar illumination, the optimized photocathode exhibited a photocurrent density of −30 mA cm⁻² at −0.5 V versus the reversible hydrogen electrode (RHE), a low onset potential of 42 mV, and a Tafel slope of 90 mV dec⁻¹, demonstrating efficient photoelectrochemical hydrogen evolution kinetics. Furthermore, the photocathode showed excellent operational stability during prolonged testing and achieved an areal hydrogen evolution rate of 202.4 μmol cm⁻² h⁻¹, outperforming many previously reported MoS₂-based photoelectrodes. The superior performance is attributed to the synergistic coupling between the highly conductive 1T phase and the stable semiconducting 2H phase, which maximizes active catalytic sites while facilitating charge transport. These findings demonstrate that hybrid 1T/2H MoS₂ quantum dots are promising photoelectrode materials for efficient and sustainable solar-driven hydrogen production.