Facile room-temperature synthesis of hydroxysulfides for efficient oxygen evolution reaction

Abstract

Transition metal layered double hydroxides (LDHs) are among the most promising oxygen evolution reaction (OER) catalysts due to their abundant active sites and tunable metal composition. However, modulating metal species alone often fails to achieve optimal electronic structure. To address this, anionic regulation, such as sulfur incorporation, has been proposed as an effective strategy to further optimize the local electronic environment and enhance the OER performance. Despite this, conventional sulfurization approaches typically require harsh conditions, leading to phase transformation, lattice damage, and uneven sulfur distribution, thereby reducing structural integrity and catalytic activity. Herein, we develop a room-temperature sulfur doping strategy to introduce S²⁻ into nickel–iron-based LDH grown on nickel foam (NiFe-LDH/NF), yielding a hydroxysulfide catalyst (S-NiFe-LDH/NF) while retaining the original structure of LDH. This mild, energy-saving method enables uniform sulfur incorporation and effectively modulates the electronic states of metal sites. Importantly, the introduced sulfur ions induce enhanced surface reconstruction of the NiFe-LDH nanosheets under operating conditions, exposing more active sites and improving OER kinetics. The resulting S-NiFe-LDH/NF catalyst exhibits outstanding OER electrocatalytic performance, delivering a low overpotential of 235 mV at 200 mA cm⁻² and a small Tafel slope of 45.3 mV dec⁻¹ in 1.0 M KOH, significantly outperforming the pristine NiFe-LDH/NF and commercial RuO₂. Moreover, it demonstrates excellent long-term durability, maintaining over 90% of its initial current after 100 hours of continuous operation. This work presents a scalable structure-preserving strategy for sulfur doping in LDH-based electrocatalysts, offering a promising approach to design high-performance OER catalysts for sustainable hydrogen production via water electrolysis.