Synergistic Effect of N‐NiMoO4/Ni Heterogeneous Interface with Oxygen Vacancies in N‐NiMoO4/Ni/CNTs for Superior Overall Water Splitting

Abstract The exploring of economical, high‐efficiency, and stable bifunctional catalysts for hydrogen evolution and oxygen evolution reactions (HER/OER) is highly imperative for the development of electrolytic water. Herein, a 3D cross‐linked carbon nanotube supported oxygen vacancy (V o )‐rich N‐NiMoO 4 /Ni heterostructure bifunctional water splitting catalyst (N‐NiMoO 4 /Ni/CNTs) is synthesized by hydrothermal‐H 2 calcination method. Physical characterization confirms that V o ‐rich N‐NiMoO 4 /Ni nanoparticles with an average size of ≈19 nm are secondary aggregated on CNTs that form a hierarchical porous structure. The formation of Ni and NiMoO 4 heterojunctions modify the electronic structure of N‐NiMoO 4 /Ni/CNTs. Benefiting from these properties, N‐NiMoO 4 /Ni/CNTs drives an impressive HER overpotential of only 46 mV and OER overpotential of 330 mV at 10 mA cm −2 , which also shows exceptional cycling stability, respectively. Furthermore, the as‐assembled N‐NiMoO 4 /Ni/CNTs||N‐NiMoO 4 /Ni/CNTs electrolyzer reaches a cell voltage of 1.64 V at 10 mA cm −2 in alkaline solution. Operando Raman analysis reveals that surface reconstruction is essential for the improved catalytic activity. Density functional theory (DFT) calculations further demonstrate that the enhanced HER/OER performance should be attributed to the synergistic effect of V o and heteostructure that improve the conductivity of N‐NiMoO 4 /Ni/CNTs and facilitatethe desorption of reaction intermediates.