Enhanced electrocatalytic hydrogen evolution over a two-dimensional Ti₃C₂ MXene/FDU-12 templated-nanoporous NiO-decorated carbon paste electrode

Noble metal-free electrocatalysts have become a crucial component for efficient hyrogen production through the electrochemical hydrogen evolution reaction (HER). Notably, MXene, a unique two-dimensional (2D) transition metal carbide/nitride material, has shown several advantageous properties such as, excellent conductivity, stability, and high surface area, which are promising as electrocatalyst for HER, especially in the alkaline electrolytes. Herein, we design an Ti₃C₂ MXene electrocatalyst decorated by the nanoporous nickel(II) oxide (NiO) on the carbon-paste electrode (CPE), coded as CPE-MXene/n-NiO. The electrochemical HER evaluation demonstrates that CPE-MXene/n-NiO has the best performance with an overpotential of 233 mV at a current density of 10 mA cm⁻². Other electrodes, bare CPE, CPE-MXene, and CPE-n-NiO shows lower overpotentials of 630 mV, 415 mV, and 396 mV, respectively, at the same current density. Moreover, CPE-MXene/n-NiO also displays the lowest Tafel slope (24 mV dec⁻¹) with a stable performance after 1000 cycles. The unique combination of MXene's layered structures with nanoporosity of n-NiO provides seamless difussion, whereas the highly electroconductive properties of MXene are beneficial for fast charge transfer. In addition, the density functional theory (DFT)-based calculations indicate that the balance between H* adsorption and desorption is most optimized at the interface of MXene and NiO, which substantially enhances the hydrogen evolution reaction.