In situ construction of S-doped NiFe-layered double hydroxide nanoarrays on porous reduced graphene oxide as efficient oxygen evolution electrocatalysts for electrolytic cells

The application of NiFe-layered double hydroxide (NiFe-LDH) as electrocatalysts for oxygen evolution reaction (OER) is seriously limited owing to low conductivity, insufficient active sites and self-aggregation. The construction of anion-doped NiFe-LDH nanoarray structures with ideal electrochemical activity is an effective strategy. Herein, we report a facile solvothermal approach for the synthesis of S-doped NiFe-LDH nanosheets loaded in situ on porous reduced graphene oxide (rGO) to form a composite with nanosheet array structure (S-NiFe-LDH/rGO) for OER. The S-NiFe-LDH/rGO nanosheet array ensures a large specific surface area, abundant accessible active sites and high stability. The moderate S doping in NiFe-LDH can tune the local electronic structures of Ni and Fe to optimize the binding of metal sites with reaction intermediates, thus enhancing the OER activity. The S-NiFe-LDH/rGO electrocatalyst shows the small OER overpotential of 264 mV at 10 mA cm⁻² and the low Tafel slope of 55 mV dec⁻¹. Moreover, S-NiFe-LDH/rGO displays good durability and structural stability due to the strong anchoring effect. The assembled two-electrode S-NiFe-LDH/rGO||Pt electrolytic cell exhibits a low cell voltage of 1.53 V at 10 mA cm⁻², which is superior to the RuO₂||Pt benchmark cell (1.60 V), indicating the practical feasibility for water electrolysis. This design strategy provides a promising insight into the fabrication of advanced OER non-noble metal electrocatalysts.