Binary Ni-Cu nanocomposite-modified MXene-adorned 3D-nickel foam for effective overall water splitting and supercapacitor applications

Herein, a multifunctional binary nickel-copper-modified MXene on nickel foam was synthesized and employed as an electrode material for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), overall water splitting and supercapacitors. This work focused on the synthesis of a binder-free electrode, where 2-dimensional MXene was electrodeposited onto nickel foam, followed by the electrodeposition of nickel-copper (NixCuyMX-NF) bimetallic heterostructures using the co-electrodeposition or sequential electrodeposition technique. Compared to the bare nickel foam and electrodeposited MXene-based nickel foam, the co-deposition of Ni-Cu resulted in agglomerated structures and good electrocatalytic activity towards HER, OER and supercapacitor application. Alternatively, it is interesting to note that owing to the uniform coverage of copper particles on the surface of nickel on the electrodeposited MXene/nickel foam (MX-NF), the electrode (NiCuMX-NF) with copper particles as the top layer generated by sequential electrodeposition was superior to the other electrocatalysts. The combined effects of MXene and binary nickel-copper on the nickel foam support enhanced the catalytic activity of the composite in energy conversion for electrochemical water splitting, exhibiting a current density of 10 mA cm-2 with a Tafel slope of 104 mV dec-1 at an overpotential (eta) of 111.14 mV for hydrogen evolution reaction (HER) and Tafel slope of 146.1 mV dec-1 at an overpotential (eta) of 185.2 mV for oxygen evolution reaction (OER) in alkaline medium. Furthermore, the potential of NiCuMX-NF for energy storage as an electrode material was investigated together with other synthesised electrocatalysts, which was shown to be a good specific capacitance supercapacitor with the cyclic retention of 70.4% after 5000 cycles. Thus, the results of this study highlight that the prepared electrocatalyst can be applied as a multifunctional electrode for energy conversion and storage devices. Herein, a multifunctional binary nickel-copper-modified MXene on nickel foam was synthesized and employed as an electrode material for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), overall water splitting and supercapacitors.