Synergism and anion-cation dual chemical substitution in heterostructure sprouted on MXene enable high-efficiency and stable overall water splitting

Abstract

The exploration of novel, super-potent and low-cost electrocatalysts for water splitting has always been the kernel in the field of renewable sources. Herein, exfoliated Ti3C2Tx MXenes work as a substrate to vertically grow polypore N,Ni-Co2P nanoarrays (N,Ni-Co2P@TC) through an in situ interface-growth strategy and subsequent phosphorization and nitridation. The well-defined heterointerfaces with positive and negative ions co-modulation as coupled hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts for efficient overall water splitting are investigated, which possesses excellent durability even at a large current density (±500 mA cm-2). For HER, suitable H2O* and H* absorption energies and accelerated electronic transmission make N,Ni-Co2P@TC display a low overpotential of 27 mV at -10 mA cm-2 and Tafel slope of 38 mV dec‑1 in 1 mol/L KOH. For OER, the synergy of N,Ni-Co2P@TC with self-reconfiguration can give enhanced activity with a low overpotential of 232 mV at 10 mA cm-2 and a Tafel slope of 57 mV dec‑1. Additionally, the excellent bifunctional activity allows easily combining for efficient overall water splitting with a low driving voltage (1.51 V) at 10 mA cm-2, and the electrolyzer can be driven by a 1.5 V AAA battery.