Transient potential oscillation-driven vertically-aligned cobalt hydroxide nanosheet as non-noble bifunctional electrocatalyst for water splitting

Highly efficient, low cost, durable electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are essential for the sustainable production of hydrogen and oxygen gases through complete water splitting. Owing to their high surface area, electrochemical activity, and stability, layered metal hydroxides have been identified as an efficient catalyst for various electrochemical reactions. This study demonstrates the HER and OER from the vertically aligned cobalt hydroxide nanosheets. The catalyst was coated on glassy carbon substrate by galvanostatic electrodeposition in the presence of 1,4-Butynediol additive. The transient potential oscillations during the deposition results in vertically aligned network of β-Co(OH)₂ nanosheets. The duration of deposition was optimized based on the OER and HER activity. This electrode (CH-500) shows overpotentials of 370 mV and 300 mV to attain 10 mA cm⁻² and a Tafel slope of 52 mV dec⁻¹ and 68 mV for OER and HER, respectively, in alkaline medium. The open-pore structure of the electrode, with 60% higher electrochemically active surface area compared to bulk, facilitates efficient oxyhydroxide formation. Moreover, this binder-free electrodeposited electrode has 80% lower charge transfer resistance than its bulk counterpart. Therefore, the developed vertically aligned β-Co(OH)₂ nanosheet could be a cost-effective efficient catalyst for water splitting.