Strain induced rich planar defects in heterogeneous WS2/WO2 enable efficient nitrogen fixation at low overpotential

Abstract

Suppression of the competitive hydrogen evolution reaction (HER) and creation of new active sites have been considered to be the most effective methodology to design efficient electrocatalysts for the nitrogen reduction reaction (NRR). Here, we report a heterogeneous WS₂/WO₂ electrocatalyst with abundant planar defects at the heterointerface ascribed to the strain effect induced by the mismatched lattice spacing between WS₂ and WO₂, which enables efficient electrocatalysis toward the NRR with a faradaic efficiency of 13.5% and an NH₃ yield rate of 8.53 μg_NH3 h⁻¹ mg_cat.⁻¹ at −0.1 V vs. RHE in acidic medium compared to bare WS₂ with a faradaic efficiency of 7.87% and an NH₃ yield rate of 6.99 μg_NH3 h⁻¹ mg_cat.⁻¹. The superior NRR electrocatalytic activity of heterostructured WS₂/WO₂ is attributed to the introduction of WO₂ effectively impeding the HER catalysis because of the blocking of edge defects in WS₂ and simultaneously creating planar defects at the WS₂/WO₂ heterointerface as active sites for stable NRR catalysis. The extraordinary NRR electrocatalytic activity of WS₂/WO₂ is further confirmed by NMR measurements and density functional theory (DFT) calculations demanding comparably lower uphill free energy for the rate-determining step of NRR catalysis, i.e. formation of NNH species. This work offers useful information for constructing efficient NRR electrocatalysts.