Active Nickel Derived from Coordination Complex with Weak Inter/Intra-molecular Interactions for Efficient Hydrogen Evolution via a Tandem Mechanism

Abstract Pyrolysis of coordination compounds to synthesize efficient non-noble metal based electrocatalysts has been regarded as a useful tactic, but few efforts have been made in correlating the inter/intra-molecular interactions of the precursor complexes to the electrocatalytic properties of the final pyrolytic products. Herein, three coordination complexes with varied inter/intra-molecular interactions, including Ni(DMG), Ni(BDC), and Ni(BDC-NH2) are employed as the precursors to fabricate metallic nickel particles for catalyzing HER in alkaline conditions. It is found the complex with a weaker inter/intra-molecular interaction requires a lower hydrogen-assisted decomposition temperature, which in turn produces less-ripened nickel particles but exhibiting higher electrochemical activity, evidenced by the V-shaped temperature dependence of HER kinetics. The best catalyst of Ni(DMG)250 presents an overpotential of only 85 mV to reach 10 mA cm-2, close to that of commercial Pt/C, and is ascribed to a tandem reaction scheme on the Ni/Ni(OH)2 heterojunctions formed on the highly active nickel surface.