Chalcogen-dependent catalytic properties of RuX₂ (X = S/Se/Te) nanoparticles decorated carbon nanofibers for hydrogen evolution in acidic and alkaline media

Transition metal dichalcogenides (TMDs), with the general formula MX₂ (M = Mo/W/Fe/Co/Ni, etc.; X = S/Se/Te), have attracted extensive research interests for hydrogen evolution reaction (HER). Compared with numerous studies on noble-metal-free TMDs, the chalcogen-dependent HER catalytic properties of noble-metal-based TMDs are lack of sufficient research attention. Herein, a facile electrospinning-assisted synthetic strategy is proposed to synthesize ruthenium dichalcogenides (RuX₂, X = S/Se/Te) nanoparticles decorated carbon nanofibers (CNFs). Benefiting from the identical nanofibrous morphology and exposed crystal planes of RuX₂ (111), the catalytic activities of RuX₂@CNFs samples were investigated and compared in a fair and direct manner. Detailed electrochemical measurements coupled with density functional theory calculations were carried out to probe their intrinsic HER catalytic activities, resulting in the catalytic activity order of RuS₂@CNFs > RuSe₂@CNFs > RuTe₂@CNFs in acidic media and that of RuS₂@CNFs > RuTe₂@CNFs > RuSe₂@CNFs in alkaline media. The superior catalytic performance of RuS₂@CNFs mainly stems from the relative lower HER energy barriers and thereby the higher intrinsic catalytic activity of RuS₂ (111), leading to ultralow overpotentials of 44 and 9 mV at 10 mA·cm⁻² in acidic and alkaline media, respectively. RuSe₂ (111) is endowed with the more optimized Gibbs free energy of hydrogen adsorption (ΔG_H*) than RuTe₂ (111), but RuTe₂ (111) shows enhanced catalytic property for H₂O dissociation and OH⁻ desorption than RuSe₂ (111), therefore, resulting in the altered catalytic activity sequences for RuSe₂ and RuTe₂ in acidic and alkaline media.