The development of earth-friendly efficient electrocatalysts for the oxygen evolution reaction (OER) becomes crucial for renewable energy production. In this work, green synthesized reduced cobalt ferrocyanide at different time intervals (RCFC-t) was demonstrated as an effective and long-lasting electrocatalyst for the OER process. The RCFC-10 loaded glassy carbon electrode runs at an overpotential of 321 mV (1.55 V) at 10 mA cm–2, and a lower overpotential of 291 mV exhibited by the optimal RCFC-10/nickel foam was almost comparable to the benchmark catalyst, such as IrO2. This newborn RCFC-10 shows excellent OER performance and durability over 250 h with 4.1% potential loss in alkaline medium. At 1.58 V, the solar-driven water electrolysis demonstration supports the efficiency of a newborn electrocatalyst in solar-to-hydrogen conversion. These research findings confirm that low-cost greener synthesized RCFC-10/NF can be used for large-scale hydrogen generation.

The development of high-performance catalysts for oxygen-evolution reaction (OER) is paramount for cost-effective conversion of renewable electricity to fuels and chemicals.

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–2@1.66 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.