Engineering Ru catalysts on sulfur-vacancy-rich MoS2 via Co doping and CO dual-functional regulation for enhanced alkaline HER

The alkaline hydrogen evolution reaction (HER) suffers from sluggish kinetics, mainly due to the high energy barrier for water dissociation and mismatched adsorption-desorption balance of key intermediates (H* and OH*). To address this challenge, this study employs a dual-functional strategy combining Co doping and in-situ CO regulation to construct a Co-MoS 2 support with abundant sulfur vacancies (Sᵥ). These Sᵥ can efficiently anchor Ru species as highly dispersed, electron-deficient Ru 4+ state, which leads to excellent alkaline HER performance of Ru 8% @Co-MoS 2 -CO by displaying a low overpotential of 46 mV at 10 mA cm −2 and a Tafel slope of 62 mV dec −1 . Combined experimental characterization and DFT (density functional theory) calculations reveals that Co-Sᵥ synergy not only optimizes Ru’s electronic structure with downshift d band center but also finely modulates the electronic properties of adjacent S site, which thereby enables precise tuning of the adsorption/desorption (ADT) behavior of OH* and H*. Meanwhile, the significantly increased electronic density around the Fermi energy (E F ) leads to enhanced efficiently electronic conductivity of Ru 8% @Co-MoS 2 -CO, as also verified by the SECM measurement, which constitutes another key factor leading to its excellent alkaline HER activity. In addition to that, it is also interestingly found that there probably also exists another route for H evolution, wherein the H* can migrate from the S site to the Ru site by crossing a low energy barrier of 0.83 eV and be evolved into H 2 by following Tafel route, jointly boosting reaction efficiency. Generally, present work provides atomic-scale insights and references for designing high-performance electrocatalysts via defect engineering-regulated metal-support interactions, which would favor other highly-efficient alkaline HER catalyst designs.