Constructing suitable heterostructured electrocatalysts and understanding their interfacial effects have been considered as an effective strategy to improve the intrinsic activity of electrocatalytic hydrogen evolution reaction (HER). In this work, ultra-small Co₃S₄-MoS₂ heterostructure was synthesized using a precursor solubility controlling method. It is found that the electrocatalytic HER performance of the heterostructured catalysts exhibited a low overpotential of 260 mV at 100 mA cm⁻² in 1.0 M KOH and possessed remarkable stability over 100 h continuous electrolysis at high current density (100 mA cm⁻²). Besides, Co₃S₄-MoS₂ electrocatalyst is applied as the cathode material for a homemade membrane electrode device for water electrolysis to produce hydrogen. It shows that the electrocatalyst has a comparable catalytic activity to that of 20% Pt/C catalyst at 70 °C. The outstanding performance of the ultra-small Co₃S₄-MoS₂ heterostructure is attributed to the efficient mass transport benefitting from its unique ultra-small hollow structure and the rapid electron transfer at the interface between Co₃S₄ and MoS₂. XPS characterizations and DFT calculations confirm that the interfacial polarization and the corresponding electron transfer from Co₃S₄ to MoS₂ at the interface optimizes the charge state of the catalyst and tunes the binding strength to the intermediates during each elementary step of the HER process. To be exact, the electron transfer promotes the adsorption of OH* on the charge-depleted Co₃S₄ sites and the adsorption of H* on the charge-enriched MoS₂ sites, respectively, thereby reducing the free energy barrier of the water dissociation step (rate-limiting step) and improving the reaction kinetics. The solubility controlling strategy may provide a novel idea for rational design and synthesis of superior stability transition metal sulfides HER electrocatalysts.

构建合适的异质结构电催化剂并了解它们的界面效应已被认为是提高电催化析氢反应 (HER) 内在活性的有效策略。在这项工作中，使用前体溶解度控制方法合成了超小 Co ₃ S ₄ -MoS ₂异质结构。发现异质结构催化剂的电催化HER性能在1.0 M KOH中100 mA cm ^-2下表现出260 mV的低过电位，并且在高电流密度（100 mA cm ^-2）下连续电解100小时后具有显着的稳定性。此外，Co ₃ S ₄ -MoS ₂电催化剂用作自制膜电极装置的阴极材料，用于水电解制氢。这表明电催化剂具有一个在 70°C 下，其催化活性与 20% Pt/C 催化剂相当。超小Co ₃ S ₄ -MoS ₂异质结构的优异性能归功于其独特的超小空心结构和Co ₃ S ₄和MoS ₂之间界面处的快速电子转移所带来的高效传质。XPS 表征和 DFT 计算证实了界面极化和相应的从 Co ₃ S ₄到 MoS _{2 的}电子转移在界面处优化催化剂的电荷状态，并在 HER 过程的每个基本步骤中调整与中间体的结合强度。确切地说，电子转移分别促进了 OH* 在电荷耗尽的 Co ₃ S ₄位点上的吸附和 H* 在电荷富集的 MoS ₂位点上的吸附，从而降低了水解离的自由能垒步骤（限速步骤）并改善反应动力学。溶解度控制策略可以为合理设计和合成具有优异稳定性的过渡金属硫化物HER电催化剂提供新的思路。