Synergistic Co-doping and Te-defects engineering in NiTe2 single-crystals for enhanced hydrogen evolution in acidic and alkaline environments

Abstract

Transition metal dichalcogenides (TMDs) are promising hydrogen evolution reaction (HER) catalysts due to their layered structures and tunable electronic properties. However, NiTe₂ suffers from suboptimal hydrogen adsorption energy (ΔG_H*) and low active site density. Here, we propose a synergistic strategy involving Co doping and Te vacancy engineering to optimize HER performance in both acidic and alkaline electrolytes of Ni_1−xCo_xTe₂ single crystals. Co²⁺ doping induces linear contraction of the a-axis lattice parameter, reducing charge transfer resistance by 80%. The synchronously formed Te vacancies significantly increase active site density, as evidenced by a 31% enhancement in double-layer capacitance. Optimized Ni_0.6Co_0.4Te₂ achieves near-ideal ΔG_H* (−0.0345 eV), delivering ultralow overpotentials of 419 mV (acidic) and 362 mV (alkaline) at 10 mA cm⁻²—17% and 26% lower than pristine NiTe₂ respectively—with >80 h stability. This work establishes a scalable strategy for designing bifunctional electrocatalysts operable in acidic and alkaline media.