Entwined Co(OH)<sub>2</sub> <i>In Situ</i> Anchoring on 3D Nickel Foam with Phenomenal Bifunctional Activity in Overall Water Splitting
Sundarraj Sriram, Selvam Mathi, Bakthavachalam Vishnu, Jayaraman Jayabharathi
Abstract
We report a promising synthetic method for the binder-free synthesis of a low-cost and efficient solar-driven electrolyzer [Co(OH)2/NF] consisting of earth abundant cobalt metal which can be employed for hydrogen (and oxygen) generation in 1 M KOH. The direct growth of Co(OH)2 on nickel foam (NF) [Co(OH)2/NF)] makes this an effective bifunctional catalyst-electrode pair for water splitting with high activity and excellent stability. The Co(OH)2/NF electrode exhibits an overpotential of 182 mV (112 mV dec–1) for hydrogen evolution reaction (HER) and 281 mV (88 mV dec–1) for oxygen evolution reaction (OER) to achieve a current density of 10 mA cm–2 (without iR correction). Co(OH)2/NF displays long-term durability (150 h) with a low potential loss of 3.1 and 3.4% for HER and OER, respectively. The active bifunctional Co(OH)2/NF-electrode pair assists in constructing a water electrolyzer that affords 10 mA cm–[email protected] V. Co(OH)2/NF//Co(OH)2/NF exhibits high stability (over 150 h) with 4.1% potential loss. The earth abundant nonprecious-metal-based electrode [Co(OH)2/NF] and the solar cell structure afforded continuous evolution of hydrogen and oxygen (@1.65 V), which can be projected to allow for low-cost, large-scale hydrogen generation.