Strongly Coupled 3D N-Doped MoO₂/Ni₃S₂ Hybrid for High Current Density Hydrogen Evolution Electrocatalysis and...

Developing noble metal-free electrocatalysts toward hydrogen evolution reaction (HER) that can work well at ultrahigh current density are crucial components in renewable energy technologies. Herein, we have reported a strongly coupled 3D hybrid electrocatalyst, which consists of N-doped MoO₂ with Ni₃S₂ grown on Ni foam (N-MoO₂/Ni₃S₂ NF) through an annealing treatment, followed by a thermal ammonia reaction. This N-MoO₂/Ni₃S₂ with a particle size of ∼50 nm was evenly grown on the Ni substrate in this 3D hybrid system. Benefiting from the strong coupling effect, the N-MoO₂/Ni₃S₂ NF exhibited a high HER performance in basic media, with a small value of the Tafel slope (76 mV dec^-1) and a low potential of 517 mV at 1000 mA cm^-2, which was superior to that of Pt/C (631 mV at 1000 mA cm^-2). Experimental results revealed that constructing a coupling interface between N-MoO₂ and Ni₃S₂ facilitated the absorption and dissociation of water molecules, consequently boosting the HER activity. Additionally, the 3D N-MoO₂/Ni₃S₂ NF hybrid could act as a bifunctional electrode for both anode (biomass upgrading) and cathode (HER), which only required a lower potential of 2.08 V at 100 mA cm^-2 as compared to the overall water splitting (2.25 V) and achieved a high biomass conversion ratio of over 90%. Moreover, substituting oxygen evolution reaction by urea oxidation reaction also can assist energy-saving hydrogen evolution for 3D N-MoO₂/Ni₃S₂ NF.