Ligand-induced electronic structure and morphology regulation in Ni3S2 heterostructures for efficient bifunctional electrocatalysis

Abstract

Developing highly efficient and robust transition metal-based electrocatalysts for urea and sulfion electrolysis is crucial to the development of sustainable and clean hydrogen energy, however, is still a significant challenge. Herein, we reported a one-step synthetic protocol to fabricate terephthalic acid (TPA) anchored Ni3S2 (TPA-Ni3S2) brush-shaped nanoarrays on nickel foam (NF) skeleton. The introduction of TPA ligands simultaneously regulates the charge transfer and morphology of Ni3S2, thus optimizing the adsorption strength and increasing the number of active sites, thereby improving the catalytic performance. The optimized TPA@Ni3S2/NF exhibits superior electrocatalytic performance toward urea oxidation reaction (UOR) with a low overpotential of 1.0 V at 100 mA cm−2 and excellent operation stability, outperforming the benchmarks and many other previous reported Ni-based catalysts. More excitingly, as for sulfion oxidation reaction (SOR), the TPA@Ni3S2/NF also shows excellent activity, which merely requires 0.48 V to achieve current densities of 100 mA cm−2. Researches of the mechanism by XPS and in-situ Raman spectroscopy revealed abundant active NiOOH derivatives originated from the surface reconstruction of TPA@Ni3S2/NF, which promoted the excellent electrocatalytic performance towards UOR. In-situ DEMS isotope tracing experiments revealed the generation of N2 was derived from urea intermolecular N–N coupling. Ex-UV–vis and in-situ UV–vis spectra further disclosed the reaction mechanism that S2− was oxidized to short-chain polysulfides that were further combined to generate S8. This work provides a feasible strategy and deep understanding to design cost-efficient electrocatalysts for energy-saving hydrogen production and simultaneously eliminating wastewater pollutants.