Multiscale modulation of ultra-small ruthenium anchored on bimetallic sulfides for seawater electrolysis at ampere-level current density

Developing efficient and stable electrocatalysts is the critical challenge for hydrogen evolution reaction (HER) from seawater electrolysis. The design of catalysts for seawater HER needs to consider not only high intrinsic activity determined by the electronic structure, but also favorable mass transfer at the catalyst's surface. Herein, a unique nanoarray hybrid heterojunction consisting of ultra-small Ru nanoparticle (NPs) decorated on the surface of NiMo bimetallic sulfides (NiMoSx) is proposed. This Ru/NiMoSx heterostructure delivers an ampere-level current density of 1.0 A cm-2 at an overpotential of only 208 mV in alkaline seawater, which is far superior to the performance of commercial Pt/C. In situ spectroscopy and electronic structural analysis demonstrate that the atom-level synergy between Ru NPs and NiMoSx heterostructure makes the electron transfer from Ru to Ni/Mo, weakening the interaction of Ru and H atom, eventually facilitating the H desorption. Also, the results of contact angle tests and simulation calculations reveal that the micro-level modulation of nanoarray structure favors the diffusion of electrolyte and bubble, ensuring rapid mass transfer and exposing multiple active sites. With the multiscale modulation including optimized electronic structure and fast mass transfer, both H2 generation and transportation for Ru/NiMoSx are all prompted, thus leading to outstanding seawater HER performance.