Space-confined synthesis of Co0.5Fe0.5S2 nanocubes as an efficient oxygen evolution electrocatalyst toward overall water splitting.

To accelerate the sluggish anodic oxygen evolution reaction (OER), the agglomeration restriction, the maximum utilization and enhancement of the electrical conductivity of active sites necessitate to design a highly exposed transition metal sulphides (TMSs)-based electrocatalysts with strong synergistic effect. Herein, we develop a space-confined hydrothermal synthesis method to fabricate Co0.5Fe0.5S2 nanocubes (CFS-nc) that exhibit restricted agglomeration and more exposed active sites for oxygen evolution. The electron transfer from the Fe to Co atoms through the synergistic effect in CFS-nc improves the metallic nature of the Co sites, thereby accelerating the OER activity. The cubic morphology, high surface area (37.68 m2 g-1) and porous structure (pore diameter of ∼13.97 nm) of CFS-nc expose the abundant catalytically active sites for rapid charge transfer. CFS-nc record an overpotential of 290 mV to achieve 10 mA cm-2 (η10), Tafel slope of 98 mV dec-1, low charge-transfer resistance (Rct = 1.1 Ω) and high double layer capacitance (Cdl = 6.1 mF cm-2) for the OER in alkaline media. In situ UV-vis spectroscopy analysis revealed that the OER mechanism follows the AEM pathway with rapid kinetics. Moreover, the CFS-nc∥Pt/C (+, -) electrolyzer exhibits a cell potential (η10) of 1.54 V, which is lower than that of the RuO2∥Pt/C (+, -) electrolyser (1.58 V) with excellent stability for 30 h for overall water splitting. This study introduces a promising approach to design efficient bimetallic TMS-based electrocatalysts for energy applications, particularly as anodic materials in water electrolysis.