Plasma-engineered oxygen vacancies on NiFe sulfide for highly efficient and durable oxygen evolution reaction

The oxygen evolution reaction (OER) in water splitting is a critical bottleneck due to its sluggish kinetics. To address this issue and accelerate the OER process, low-cost NiFe-based sulfides exhibit great potential for large-scale applications. However, they suffer from insufficient active sites and poor stability under high current densities, which limits their practical utility. Herein, an O₂-plasma modification strategy was proposed to precisely regulate the surface oxygen vacancy (O_V) concentration of Fe-doped Ni₃S₂ nanoblocks, thus fabricating the p-Fe-Ni₃S₂/NF catalyst. Notably, the surface O_V concentration can be finely tailored by simply adjusting the plasma exposure duration, enabling controllable modulation of the catalytic performance. In 1.0 M KOH, this catalyst required only 297 mV overpotential to reach the current density of 200 mA cm^-2, accompanied by a low Tafel slope of 54.87 mV dec^-1. Furthermore, it showed negligible activity decay after a 100 h chronopotentiometric test at 200 mA cm^-2, exhibiting superior cycling stability. The enhanced performance originated from more exposed active sites, an expanded electrochemically active surface area and accelerated electron transfer kinetics induced by plasma modification. This work provides a new avenue for the rational design of high-performance OER electrocatalysts and advanced energy conversion materials.