Enhanced electrochemical activity of Co₃O₄/Co₉S₈ heterostructure catalyst for water splitting

The dearth of efficient, robust, and economical electrocatalysts for water oxidation is dubiously the key obstacle for renewable energy devices, so synthesis of efficient, and cost-effective metal-based water oxidation catalysts is vital. Herein, Co₃O₄, Co₉S₈ catalysts and their heterostructure Co₃O₄/Co₉S₈ were synthesized and evaluated as water oxidation electrocatalysts. The characterization of Co₃O₄, Co₉S₈, and Co₃O₄/Co₉S₈ electrocatalysts was performed using Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction techniques. The heterostructure Co₃O₄/Co₉S₈ (1.46 V) exhibited water oxidation electrocatalysis at extremely low onset potential compared to Co₃O₄ (1.58 V), and Co₉S₈ (1.48 V) catalysts. A 281 mV overpotential required to attain a current density of 50 mA cm⁻² in alkaline solution (1 M KOH), outperforming most of Co-based benchmark electrocatalysts. Further, the Co₃O₄/Co₉S₈ heterojunction demonstrated catalytic activity with small Tafel slope of 37 mV dec⁻¹. The finding of electrochemical studies involving controlled potential electrolysis and long-term stability are projected to steer the future advancement in constructing efficient, economical, stable, and earth-abundant metal-based water oxidation catalysts.