Interfacial and Ligand Dual Engineering Toward Energy-Saving Hydrogen Production Coupled with Sulfion Degradation

Abstract

Electrolytic hydrogen production assisted by the sulfion oxidation reaction (SOR) offers a low-cost, energy-efficient alternative to conventional methods by replacing the anodic oxygen evolution reaction (OER), which reduces the required anode potential. However, scaling this technology requires bifunctional electrocatalysts that efficiently drive SOR and sustain the hydrogen evolution reaction (HER) at high current density in concentrated sulfion electrolytes. Herein, using a coordinated regulation strategy of interface and ligand, we constructed a nickel cobalt sulfide/ligand-functionalized nickel cobalt hydroxide composite catalyst (NiCo-S/NiCo-OH-CL) with rich sulfide/hydroxide heterointerfaces via a hydrothermal ion exchange method, using a metal–organic framework as the precursor. Benefiting from the porous network, sulfur-repellent hydrophilic surface, and dual electronic structure regulation from heterointerfaces and ligands, it demonstrates excellent SOR and HER activity. The constructed coupled electrocatalytic system requires an ultra-low cell voltage of only 0.62 V at a current density of 100 mA cm⁻², achieving a cathodic hydrogen Faraday efficiency of ≥95% and operational stability for over 3200 h or 133 days. The sulfur and hydrogen yields reach 0.36 kg h⁻¹ m⁻² and 0.036 kg h⁻¹ m⁻², respectively. This work advances a synergistic interface-ligand modulation strategy for bifunctional catalysts and demonstrates a pathway for energy-efficient hydrogen production and sulfur recovery.