Oxygen-deficient MoO x /Ni 3 S 2 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, MoO x /Ni 3 S 2 spheres comprising Ni 3 S 2 nanoparticles inside and oxygen-deficient amorphous MoO x outside in situ grow on Ni foam (NF), to assembly the heterostructure composites of MoO x /Ni 3 S 2 /NF. By adjusting volume ratio of the solvents of ethanol to water, the optimized MoO x /Ni 3 S 2 /NF-11 exhibits the best HER performance, requiring an extremely low overpotential of 76 mV to achieve the current density of 10 mA·cm −2 ( η 10 = 76 mV) and an ultra-small Tafel slope of 46 mV·dec −1 in 0.5 mol·L −1 H 2 SO 4 . More importantly, the catalyst shows prominent high catalytic stability for HER (> 100 h). The acid-resistant MoO x wraps the inside Ni 3 S 2 /NF to ensure the high stability of the catalyst under acidic conditions. Density functional theory calculations confirm that the existing oxygen vacancy and MoO x /Ni 3 S 2 heterostructure are both beneficial to the reduced Gibbs free energy of hydrogen adsorption (∣Δ G H* ∣) 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 MoO x /Ni 3 S 2 /NF is promising to serve as a highly effective and durable electrocatalyst toward HER.