Oxygen-deficient MoOx/Ni3S2 heterostructure grown on nickel foam as efficient and durable self-supported electrocatalysts for hydrogen evolution reaction

High-performance and ultra-durable electrocatalysts are vital for hydrogen evolution reaction (HER) during water splitting. Herein, by one-pot solvothermal method, MoOx/Ni3S2 spheres comprising Ni3S2 nanoparticles inside and oxygen-deficient amorphous MoOx outside in situ grow on Ni foam (NF), to assembly the heterostructure composites of MoOx/Ni3S2/NF. By adjusting volume ratio of the solvents of ethanol to water, the optimized MoOx/Ni3S2/NF-11 exhibits the best HER performance, requiring an extremely low overpotential of 76 mV to achieve the current density of 10 mA & BULL;cm(-2) (eta(10) = 76 mV) and an ultra-small Tafel slope of 46 mV & BULL;dec(-1) in 0.5 mol & BULL;L-1 H2SO4. More importantly, the catalyst shows prominent high catalytic stability for HER (> 100 h). The acid-resistant MoOx wraps the inside Ni3S2/NF to ensure the high stability of the catalyst under acidic conditions. Density functional theory calculations confirm that the existing oxygen vacancy and MoOx/Ni3S2 heterostructure are both beneficial to the reduced Gibbs free energy of hydrogen adsorption ( divide & UDelta;G(H*) divide ) over Mo sites, which act as main active sites. The heterostructure effectively decreases the formation energy of O vacancy, leading to surface reconstruction of the catalyst, further improving HER performance. The MoOx/Ni3S2/NF is promising to serve as a highly effective and durable electrocatalyst toward HER.

Automated summary

A high-performance and ultra-durable electrocatalyst MoOx/Ni3S2/NF with MoOx/Ni3S2 heterostructure is synthesized by solvothermal method. The optimized catalyst MoOx/Ni3S2/NF-11 exhibits excellent hydrogen evolution reaction (HER) performance with low overpotential and small Tafel slope. It also shows high catalytic stability for more than 100 hours. The heterostructure and oxygen vacancy contribute to the improved HER performance by reducing Gibbs free energy and facilitating surface reconstruction.