Understanding the synergistic effect of Ce-doping and carbon-encapsulating in NiCoP for enhanced stability and activity for overall water splitting

The overall water splitting (OWS) plays a fundamental role in sustainable energy technologies. However, creating non-precious metal electrocatalysts with high activity and durability under alkaline conditions is of great significance but remains challenging. Herein, the aim of this work is to overcome this challenge by creating Ce-doped and carbon-encapsulated bifunctional NiCoP (Ce-NiCoP@C) with nanorod array morphology onto nickel foam (NF). The doping of Ce is done by a simple one-pot hydrothermal treatment of Ni, Co, and Ce sources in an aqueous solution, and the carbon layer is introduced through simple glucose impregnation followed by pyrolysis. Both the experimental results and theoretical calculations reveal that Ce doping not only induces lattice distortion of NiCoP, enhances the structural stability, but also promotes the firm bonding of the carbon layer onto the surface of NiCoP, and thus greatly inhibits the carbon layer from falling off. As a result, the Ce-NiCoP@C/NF displays remarkable long-term stability for 200 h as bifunctional electrodes in OWS. Importantly, benefiting from the unique nanorod array morphology, microenvironment optimization of Ce, and expanded active surface area originating from the carbon layer, the Ce-NiCoP@C/NF electrode exhibits excellent HER and OER activity with a corresponding overpotential of 37 mV and 255 mV at 10 mA cm−2. In addition, it achieves a low cell voltage of 1.51 V at 10 mA cm−2 in OWS, which improves by 14 % compared to that of RuO2(+)||Pt-C(−) coupled electrolyzer. This work provides a new inspiration for further design and construction of nonprecious metal-based bifunctional electrocatalysts with excellent intrinsic activity and outstanding durability.