Synchronously anchoring of Ni12P5–Ni2P heterojunction nanoparticles in the 3D graphene composite bonded by N–P co-doped porous carbon as an efficient bifunctional catalyst for alkaline water splitting

Designing and synthesizing cost-effective hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts is still the critical impetus for electrocatalytic alkaline water splitting for green hydrogen production. We present a novel strategy to synthesize Ni12P5–Ni2P heterojunction nanoparticles anchored in the three-dimensional (3D) graphene composite bonded by N–P co-doped porous carbon (NPC) through a single high-temperature carbonization. The as-obtained Ni12P5–Ni2P@NPC/3DG possessed an open pore structure, promoting electrolyte diffusion and enhance bubble release. The synergistic effect of the Ni12P5–Ni2P heterojunction with high intrinsic catalytic activity and the N–P co-doped carbon enabled the composite to exhibit high catalytic activity and stability for HER and OER. The optimized Ni12P5–Ni2P@NPC/3DG-0.5 exhibited overpotentials of 209.8/206.1 mV at 10 mA cm−2 and Tafel slopes of 67.9/92.3 mV dec−1 for HER/OER. Furthermore, when Ni12P5–Ni2P@NPC/3DG-0.5 was used as both the cathode and anode for overall water splitting, the cell only required a low voltage of 1.58 V to achieve a current density of 10 mA cm−2, which was comparable to the catalytic activities of commercial noble metal catalysts. Meaningfully, this synthetic method provided a new strategy to improve electrocatalytic performance of Ni-based phosphides, extensively promoting the development of highly efficient electrocatalysts for alkaline overall water splitting.