A facile approach to high-performance trifunctional electrocatalysts by substrate-enhanced electroless deposition of Pt/NiO/Ni on carbon nanotubes

Abstract

Trifunctional electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are crucial for many electrochemical devices. Herein, novel trifunctional electrocatalysts of a hierarchically-structured Pt/NiO/Ni/CNT with ultrasmall Pt nanoparticles (∼2 nm) were synthesized via substrate-enhanced electroless deposition. The resulting catalysts exhibited a higher ORR activity (half-wave potential at 0.942 V) than that of the benchmark commercial Pt/C (20 wt%) and a similar OER activity (overpotential of 350 mV at 10 mA cm⁻²) to that of RuO₂ in alkaline media. Moreover, the newly-developed Pt/NiO/Ni/CNT catalysts also showed a high mass activity superior to Pt/C towards the HER in both acid and alkaline electrolytes. The Pt/NiO/Ni/CNT catalysts, when used for overall water splitting, self-powered by two Zn–air batteries with the Pt/NiO/Ni/CNT air electrodes connected into series, displayed superb performance with 1.61 V at 10 mA cm⁻². This work represents a breakthrough in the development of facile approaches to trifunctional catalysts from low-cost Earth-abundant materials for efficient energy conversion and storage.