Phase Engineering of Molybdenum Dichalcogenide to Anion-Tunable Polyphasic Quaternary Chalcogenide (2H/1T/1T′) MoS_xSe_yTe_z (x + y + z = 2) Amplifies the Growth of H₂ Electrolytically

Herein, we report first anion-tunable quaternary molybdenum chalcogenides (QMC, MoSxSeyTez, x + y + z = 2) with multiple phases [2H (29.7%), 1T (33.54%), 1T′ (36.76%)] for comparative hydrogen evolution reaction (HER) studies with molybdenum dichalcogenides (MDC) and ternary molybdenum chalcogenides (TMC). The multiple-phase inclusion with the help of incorporation of different chalcogen atoms in single catalysts is a significant aspect for producing green H2 efficiently. QMC presents a superior response than MDC and TMC in acidic and PBS media due to binary to ternary phase transition. The optimal MoS0.5Se1Te0.5 delivers admirable electrocatalytic activity (overpotential of 111 mV at 2 mA cm–2, Tafel slope of 62 mV dec–1, 96% Faradaic efficiency, 45 μmol h–1) in 0.5 M H2SO4 with superb stability. Employing density functional theory over MoS0.5Se1Te0.5, the computed overpotential matches nicely with the experimental data, showing the ΔG value of ∼0.098 eV. The polytypic (2H/1T/1T′) phase consolidation modifies the electronic structure of Mo’s d band and directly affects the growth of HER.