Ni-Doped Co-Based Metal–Organic Framework with Its Derived Material as an Efficient Electrocatalyst for Overall Water Splitting

Composite catalysts combining a metal–organic framework (MOF) with its derivatives have attracted significant attention in electrocatalysis due to their unique properties. In this study, we report the synthesis of a Ni-doped Co-1,4-benzenedicarboxylate (defined as Co3Ni1BDC) metal–organic framework via a straightforward solvothermal method, aiming to enhance oxygen evolution reaction (OER) activity. The introduction of Ni modulated the electronic structure, yielding high catalytic activity with an overpotential (η100) of 300 mV and excellent stability for the OER. The Co3Ni1BDC material was further encapsulated with Co2P nanoparticles via a controlled phosphating annealing process, forming a hybrid electrocatalyst (Co3Ni1BDC@Co2P) to boost hydrogen evolution reaction (HER) performance. The Co3Ni1BDC@ Co2P catalysts exhibited superior HER performance with low overpotentials of η10 = 20 mV and η100 = 127 mV, outperforming the Co3Ni1BDC precursor. An alkaline electrolyzer assembled with Co3Ni1BDC//Co3Ni1BDC@Co2P achieved a cell voltage of 1.70 V at a current density of 20 mA cm−2. This work provides a valuable idea for designing efficient electrocatalysts for overall water splitting.