Tunable decoration of Ni/Ni3N nano-heterostructures on N-defective g-C3N4 via topochemical self-nitridation for efficient electrocatalytic overall water splitting

The growth of base-metal-based heterostructures on metal-free carriers is considered an effective strategy for designing low-cost high-efficiency hybrid electrocatalysts with electronic modulation for bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as further overall water splitting (OWS). Herein, Ni/Ni3N heterostructures with regulable composition are grown in-situ on N-defective graphitic carbon nitride (g-C3N4) through a novel ammonia-free topochemical self-nitridation route. Benefitting from the synergetic effect between Ni/Ni3N heterointerface and the strong support of g-C3N4 carrier, the as-fabricated Ni/Ni3N/g-C3N4 composite performs superior capacity toward both HER and OER in alkaline conditions. The optimal Ni/Ni3N/g-C3N4 sample requires low overpotentials for HER (55 mV) and OER (253 mV) to drive a current density of 10 mA cm−2, along with long-term durability. Furthermore, the constructed Ni/Ni3N/g-C3N4 (+||−) electrolytic cell for alkaline OWS can afford a current density of 10 mA cm−2 under a voltage of 1.556 V with outstanding stability.