Ultrathin NiCo2Px nanosheets strongly coupled with CNTs as efficient and robust electrocatalysts for overall water splitting

Abstract

Hydrogen is a promising energy carrier that becomes an alternative to fossil fuels due to its recyclability and pollution-free nature. Water splitting is an effective method for high purity hydrogen production; however, it requires efficient, low-cost and durable catalysts. Herein, a facile method to synthesize self-assembled 3D laminar NiCo₂P_x anchored on functionalized carbon nanotubes (NiCo₂P_x/CNTs) is developed for achieving cost-efficient, highly-active, and robust electrocatalysts towards overall water splitting in 1 M KOH. Notably, the overpotentials at a current density of 10 mA cm⁻² are as low as 47 and 284 mV for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. The water electrolyzer device using NiCo₂P_x/CNTs as both the cathode and anode only requires a cell voltage of 1.61 V to reach a current density of 10 mA cm⁻² along with outstanding durability for at least 48 h. Furthermore, the catalytic mechanism was discussed with a special emphasis on the synergetic effect of Ni and Co and real OER active species. Our work not only establishes a promising electrocatalyst, but also provides a general strategy to enhance the activity and stability of metal phosphides.