Vertically-interlaced NiFeP/MXene electrocatalyst with tunable electronic structure for high-efficiency oxygen evolution reaction

Abstract

Layered double hydroxides (LDHs) with decent oxygen evolution reaction (OER) activity have been extensively studied in the fields of energy storage and conversion. However, their poor conductivity, ease of agglomeration, and low intrinsic activity limit their practical application. To date, improvement of the intrinsic activity and stability of NiFe-LDHs through the introduction of heteroatoms or its combination with other conductive substrates to enhance their water-splitting performance has drawn increasing attention. In this study, vertically interlaced ternary phosphatised nickel/iron hybrids grown on the surface of titanium carbide flakes (NiFeP/MXene) were successfully synthesised through a hydrothermal reaction and phosphating calcination process. The optimised NiFeP/MXene exhibited a low overpotential of 286 mV at 10 mA cm-2 and a Tafel slope of 35 mV dec-1 for the OER, which exceeded the performance of several existing NiFe-based catalysts. NiFeP/MXene was further used as a water-splitting anode in an alkaline electrolyte, exhibiting a cell voltage of only 1.61 V to achieve a current density of 10 mA cm-2. Density functional theory (DFT) calculations revealed that the combination of MXene acting as a conductive substrate and the phosphating process can effectively tune the electronic structure and density of the electrocatalyst surface to promote the energy level of the d-band centre, resulting in an enhanced OER performance. This study provides a valuable guideline for designing high-performance MXene-supported NiFe-based OER catalysts.