Efficient multifunctional electrocatalyst based on 2D semiconductive bimetallic metal-organic framework toward non-Pt methanol oxidation and overall water splitting

Abstract

As the efficient approaches for obtaining clean H2 energy, methanol oxidation (MOR) and water over slitting reactions have been increasingly essential. A series of novel semiconductive CoNi bimetal–organic framework (CoxNi3-x(HAB)2 MOF) have been prepared using hexaaminobenzene (HAB) as an organic linker. The obtained series of CoxNi3-x(HAB)2 MOFs were then explored as efficient multifunctional electrocatalysts for the non-Pt MOR and overall water splitting in alkaline medium. The basic characterizations of CoxNi3-x(HAB)2 MOFs revealed that they comprised multiple metal valence states (Co0/Co2+/Co3+ and Ni2+/Ni3+) and graphene-like nanostructures embedded with abundant CoNi alloy nanoparticles. Compared with the sole-metal MOFs (Co3(HAB)2 MOF and Ni3(HAB)2 MOF), the CoxNi3-x(HAB)2 MOF with a mass ratio of Co:Ni = 1:3 (CoxNi3-x(HAB)2 MOF-2) exhibited superior electrocatalytic performance for MOR. It gave a high current density of 92.8 mA cm−2 at 1.6 V vs. reversible hydrogen electrode (RHE) for MOR, along with the low overpotentials at the current density of 10 mV cm−2 (η10) and Tafel slopes toward hydrogen evolution reaction (η10 = 119 mV, Tafel slope = 46 mV dec-1) and oxygen evolution reaction (η10 = 1.35 V, Tafel slope = 26 mV dec−1). The analysis on the catalysis mechanism of MOR and water splitting in alkaline medium was also proposed. The voltages applied to the three- and two-electrode systems based on the bifunctional CoxNi3-x(HAB)2 MOF-2 catalyst for overall water splitting are 1.52 V vs. RHE and 1.45 V vs. silver/silver chloride (Ag/AgCl), respectively. This work provides a novel strategy for investigating the applications of promising two-dimensional semiconductive MOF as multifunctional electrocatalysts with boosted electrocatalytic activities in energy fields.