The effects of ball milling on microstructures of graphene/Ni composites and their catalytic activity for hydrogen evolution reaction

The effects of the ball milling on microstructures of the graphene/Ni composites and subsequent hydrogen evolution reaction in acidic solution were investigated. Ni nanoparticles with average grain size of 4 nm were uniformly dispersed on the graphene surface after short time ball milling. While amorphous characteristic was observed due to long time ball milling. The graphene/Ni composites with amorphous structure exhibited higher electrocatalytic performance than the graphene/Ni composites with nanocrystalline structure. The Volmer-Heyrovsky mechanism was found for the graphene/Ni composites with nanocrystalline structure, while the graphene/Ni composites with amorphous structure showed evident Heyrovsky mechanism. The excellent hydrogen evolution reaction and stability of the graphene/Ni composites could be attributed to superior interfacial contact, amorphous Ni, and synergistic effect between amorphous Ni and high conductive graphene.