Ni-MoO2 nanoparticles heterojunction loaded on stereotaxically-constructed graphene for high-efficiency overall water splitting

Abstract

The development of heterostructures is an effective way to improve the efficiency of water decomposition. More heterojunction with smaller size is an important strategy to improve the utilization efficiency of non-noble metal active substances and further improve catalytic activity. Herein, the stereotaxically-constructed graphene (SCG) was synthesized by cationic exchange resin and was used as the substrate to prepared Ni-MoO2@SCG nanoparticles heterojunction (Ni is surrounded by MoO2) for the first time by hydrothermal process and annealing method. In urea solution, porous SCG restricted the transition of nanoparticles to microspheres, inhibited the aggregation of active substances, and provided a large number of anchoring sites for nanoparticles. In the process of high-temperature hydrogen reduction, Ni atoms precipitate to form nano-particles and form unique heterojunction particles of about 20 nm with MoO2. The synergistic effect at the interface between Ni and MoO2 significantly enhances the catalytic activity of MoO2. The as-prepared Ni-MoO2@SCG sample exhibits overpotentials of 79.97 mV and 278 mV to reach a current density of 10 mA cm−2 for HER and OER in 1.0 M KOH, respectively. More importantly, it performs stable overall water splitting with a cell voltage of 1.548 V at a current density of 10 mA cm−2 as both cathode and anode. Anchoring nano heterojunction particles on the surface of porous Stereotaxically-constructed graphene provides a new direction for improving the catalytic performance of powder's electrocatalysis.