Interface Engineering via Ti₃C₂T_x MXene Enabled Highly Efficient Bifunctional NiCoP Array Catalysts for Alkaline Water Splitting

Developing a non-noble metal-based bifunctional electrocatalyst with high efficiency and stability for overall water splitting is desirable for renewable energy systems. We developed a novel method to fabricate a heterostructured electrocatalyst, comprising a NiCoP nanoneedle array grown on Ti₃C₂T_x MXene-coated Ni foam (NCP-MX/NF) using a dip-coating hydrothermal method, followed by phosphorization. Due to the abundance of active sites, enhanced electronic kinetics, and sufficient electrolyte accessibility resulting from the synergistic effects of NCP and MXene, NCP-MX/NF bifunctional alkaline catalysts afford superb electrocatalytic performance, with a low overpotential (72 mV at 10 mA cm^-2 for HER and 303 mV at 50 mA cm^-2 for OER), a low Tafel slope (49.2 mV dec^-1 for HER and 69.5 mV dec^-1 for OER), and long-term stability. Moreover, the overall water splitting performance of NCP-MX/NF, which requires potentials as low as 1.54 and 1.76 V at a current density of 10 and 50 mA cm^-2, respectively, exceeded the performance of the Pt/C∥IrO₂ couple in terms of overall water splitting. Density functional theory (DFT) calculations for the NCP/Ti₃C₂O₂ interface model predicted the catalytic contribution to interfacial formation by analyzing the electronic redistribution at the interface. This contribution was also evaluated by calculating the adsorption energetics of the descriptor molecules (H₂O and the H and OER intermediates).