Balancing Volmer Step by Superhydrophilic Dual-Active Domains for Enhanced Hydrogen Evolution

The reaction kinetics of hydrogen evolution reaction (HER) is largely determined by balancing the Volmer step in alkaline media. Bifunctionality as a proposed strategy can divide the work of water dissociation and intermediates (OH* and H*) adsorption/desorption. However, sluggish OH* desorption plagues water re-adsorption, which leads to poisoning effects of active sites. Some active sites may even directly act as spectators and do not participate in the reaction. Furthermore, the activity comparison under approximate nanostructure between bifunctional effect and single-exposed active sites is not fully understood. Here, a facile three-step strategy is adopted to successfully grow molybdenum disulfide (MoS₂) on cobalt-containing nitrogen-doped carbon nanotubes (Co-NCNTs), forming obvious dual active domains. The active sites on domains of Co-NCNTs and MoS₂ and the tuned electronic structure at the heterointerface trigger the bifunctional effect to balance the Volmer step and improve the catalytic activity. The HER driven by the bifunctional effect can significantly optimize the Gibbs free energy of water dissociation and hydrogen adsorption, resulting in fast reaction kinetics and superior catalytic performance. As a result, the Co-NCNTs/MoS₂ catalyst outperforms other HER electrocatalysts with low overpotential (58 and 84 mV at 10 mA cm⁻² in alkaline and neutral conditions, respectively), exceptional stability, and negligible degradation.