Incomplete amorphous phosphorization on the surface of crystalline cobalt molybdate to accelerate hydrogen evolution

The development of non-noble metal-based electrocatalysts is of great significance to the wide application of electrocatalytic hydrogen production. However, construction of a highly active surface layer with synergistic sites toward alkaline hydrogen evolution still remains challenging. Herein, a strategy of incomplete amorphous phosphorization at the surface of crystalline cobalt molybdate is proposed to realize the interface engineering of crystalline cobalt molybdate surrounded by the amorphous cobalt phosphide (CoMoO4@a-CoPx). The synergy of a-CoPx and crystalline CoMoO4 nanoparticles in the shell of the nanocomposite leads to a low overpotential of 74.7 mV at 10 mA cm(-2) and small Tafel slope of 64 mV dec(-1) toward alkaline hydrogen evolution, superior to single-phase CoMoO4 and CoPx electrocatalysts. The amorphous CoPx in the shell provides highly catalytically active sites, while the presence of crystalline CoMoO4 effectively regulates electron transfer into the active sites. The unique structure brings about more suitable water dissociation energy and hydrogen desorption energy, and prevents the deactivation of active sites, thereby promoting the catalytic activity. This work could offer alternative options for the development of efficient hydrogen evolution catalysts in an alkaline solution.