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[Display omitted] • Self-supported Al-CoSe 2 nanowire arrays were obtained. • The obtained electrocatalysts exhibit excellent catalytic activities and stability. • Possible enhanced mechanism has been convinced. The development of highly efficient, long-lasting, and earth-rich electrocatalysts for hydrogen evolution processes (HER) is crucial to the advancement of hydrogen energy. Due to its improved catalytic activity, extraordinary chemical stability, and low cost, pyrite cobalt selenide (CoSe2) has become an incredibly potential replacement for Pt-based HER electrocatalysts. However, because of limited hydrogen adsorption and accompanying restrictions in its electronic structure, its practical application has run into difficulties. Herein, we have introduced aluminum (Al) into CoSe2/CC nanowire arrays on carbon cloth using a simple hydrothermal and selenization method. The synthesized materials serve as highly effective catalysts for HER, with the optimized Al-CoSe2/CC demonstrating a significantly overpotential reduced by nearly 90 mV compared to pure CoSe2/CC (from 243 mV to 153 mV) at a current density at 10 mA cm−2 and a small Tafel slope of 88 mV dec−1. Moreover, these catalysts exhibit exceptional durability, sustaining their performance for 24 h. Based on the experimental results and subsequent density functional theory (DFT) calculations, it has been demonstrated that Al doping can significantly enhance the electronic conductivity, maximize the hydrogen evolution adsorption energy, and improve the charge transfer ability. This work offers a profound insight into the correlation between cation substitution in non-precious metal-based catalysts and the enhancement of intrinsic HER catalytic performance. [ABSTRACT FROM AUTHOR]

Exploring efficient non-precious metal sulfides as electrocatalysts for the hydrogen evolution reaction (HER) is crucial. Cobalt disulfide (CoS 2) has gained attention for its favorable intrinsic activity, impressive metal conductivity, and cost-effectiveness. However, the weak adsorption of H* at the sulfur (S) sites on the surface of CoS 2 leaves room for enhancing its HER intrinsic activity. Vacancy engineering emerges as a valuable strategy to modulate the local charge density, optimizing hydrogen adsorption free energy and catalytic performance in HER. Taking advantage of plasma technology, known for its rapid and efficient defect creation, we synthesized porous CoS 2 nanowire arrays enriched with S vacancies (V s -CoS 2 /CC) through Ar plasma treatment. Notably, at a current density of 10 mA cm−2, V s -CoS 2 /CC exhibits a lower overpotential (170 mV) compared to pure CoS 2 /CC (236 mV). Furthermore, V s -CoS 2 /CC demonstrates exceptional electrochemical stability. Experimental data and density functional theory calculations jointly reveal that introducing S vacancies reduces local charge density around S atoms, activating inert sulfur sites and enhancing the intrinsic activity of CoS 2 for HER. This study introduces a novel concept of defect-engineered activation in metal compound catalysts, employing a plasma approach to advance HER performance. [Display omitted] • By introducing V s through plasma treatment, V s -CoS 2 /CC is obtained. • V s -CoS 2 /CC exhibits excellent HER catalytic performance. • The introduction of V s activates the inert S sites in CoS 2. [ABSTRACT FROM AUTHOR]