CoO-Mo2N hollow heterostructure for high-efficiency electrocatalytic hydrogen evolution reaction

Driving the electrocatalytic hydrogen evolution reaction (HER) with solar-energy cells is considered a green and sustainable way to produce H-2. Herein, CoO-Mo2N hollow heterojunctions were designed for effective HER based on the combined virtues of the hollow structure and heterojunctions. The hollow CoMoO4-Co(OH)(2) precursor was first synthesized via the reaction of Co2+ from ZIF-67 with MoO42- and OH- in a Na2MoO4 solution. A series of experiments indicate the formation of the hollow Co-Mo-O precursor followed a mechanism analogous to the nanoscale Kirkendall Effect. After heating in NH3, the CoO-Mo2N hollow heterostructure was obtained. The Mo species in the precursor played an important role in maintaining the morphology under nitridation treatment. The hollow structure is favorable for contact and diffusion of electrolyte with (in) catalysts, while the CoO in CoO-Mo2N is favorable for the dissociation of water. Both promote the HER. Under optimized conditions, the hollow catalyst exhibited good HER performance with an overpotential of 65 mV at 10 mA cm(-2) in 1 M KOH. The performance is better than that of many nonprecious metal-based catalysts. An electrolyzer composed of CoO-Mo2N heterojunctions as the cathode and NiFe-LDH as the anode can be driven by a solar cell to achieve effective overall water splitting. The adjudication of MOFs makes the route promising for the design of robust catalysts for advanced application.