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.

Cobalt anchored polyaniline electrocatalysts (Co@PANI) have been synthesized (Co@PANI‐200, Co@PANI‐400, Co@PANI‐600, Co@PANI‐800) and characterised. The electrical conductivity and stability of Co@PANI increased due to the synergistic effect of PANI and cobalt content. PANI prevents aggregation and show strong binding with cobalt ions. The Co@PANI‐600/GC shows low overpotential of 341 mV @ 10 mA cm−2 current density and the Tafel slope of Co@PANI‐600 (39 mV dec−1) was smaller than IrO2 (98 mV dec−1) for OER. The calculated turnover frequency (TOF) of Co@PANI‐600/GC (0.01609 s−1) was ≈8 times higher than IrO2 (0.0014 s−1) at 1.60 V. Furthermore, the Co@PANI‐600/NF electrocatalyst shows an incredibly low overpotential of 251 mV @10 mA cm−2. This new born Co@PANI‐600/NF exhibits durability over 250 h with only 5.1 % potential loss in alkaline medium. Co@PANI‐600 catalyst exhibits excellent OER performances as well as having enough kinetics to solve the sluggish rate of water oxidation. At 1.54 V, the solar driven water electrolysis demonstration supports the efficiency of new born electrocatalyst in solar to hydrogen conversion. These research findings confirm that Co@PANI‐600 can be used for large‐scale hydrogen generation at the lowest possible cost.

Development of eco-friendly efficient dual electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) gaining increased attention for renewable energy production. Here, the greenly synthesized rCoFe-PBA was established as durable and effective bifunctional electrocatalyst for HER and OER process. The rCoFe-PBA coated Nickel foam electrode exhibit overpotential of 311 mV (OER) and 100 mV (HER) @ 10 mA cm À 2 significantly lower than commercial IrO 2 (381 mV) and near to Pt/C (36 mV). The rCoFe-PBA show smaller Tafel slope (OER: 57 mV dec À 1 ) than IrO 2 (78 mV dec À 1 ) and exhibit Tafel slope of 131 mV dec À 1 (HER) which is near to Pt (90 mV dec À 1 ). Turnover frequency (TOF) was estimated as 0.22 s À 1 (OER) and 0.26 s À 1 (HER) was found to be 5 and 10 times higher than IrO 2 catalyst (0.040 s À 1 ) and Pt/C catalyst (0.025 s À 1 ), respectively. For solar water electrolysis, rCoFe-PBA/NF shows overpotential of 411 mV and durability over 180 h in 1.0 m KOH (4.1 % potential loss). The combination of non-precious electrolyzer, rCoFe-PBA with commercial solar cell produced H 2 gas in alkaline water under sunlight. This methodology proves that the greenly synthesized rCoFe-PBA electrolyzer can outperform the precious electrocatalysts, implying that the cost-effective large scale H 2 production without artificial current is possible with commercial solar cells.

Developing highly active, cost‐effective, and robust electrocatalysts for the oxygen evolution reaction (OER) still remains a crucial challenge for enhancing the conversion of sustainable energy resources. The performances of existing electrocatalysts is restricted by low electronic conductivity and the limited amount of active sites. Herein, newly synthesized FeIIIOH nanoparticles (NPs) are shown to be efficient and durable electrocatalysts for the OER reaction. FeIIIOH NP‐coated nickel foam (FeIIIOH NPs/NF) operates at an overpotential of 300 mV (@10 mA cm−2) with excellent stability even after 30 h and shows higher stability relative to a cell voltage of 1.55 V in alkaline media, which is substantially lower than the commercial electrocatalyst IrO2 (1.61 V). The FeIIIOH NPs/NF overpotential of 300 mV at 10 mA cm−2 is 89 and 127 mV lower than IrO2/NF (389 mV) and NF (427 mV), respectively. The Tafel slope of FeIIIOH NPs/NF (104 mV dec−1) is lower than IrO2/NF (164 mV dec−1) and NF (199 mV dec−1). The calculated turnover frequency (TOF) of FeIIIOH NPs (0.0128 s−1) is approximately five times higher than that of the IrO2 catalyst (0.0089 s−1) at 1.60 V. This reflects that the FeIIIOH NP catalyst is intrinsically active, giving outstanding OER performances and showing satisfactory kinetics to overcome the sluggish water oxidation rate. Solar water electrolysis shows continuous evolution of oxygen and hydrogen gas at the anode and cathode, respectively, at 1.55 V. The amount of hydrogen generated during solar water electrolysis was calculated as 3.22 mmol h−1 cm−2, which is close to the coulombic efficiency at 1.55 V. This demonstration develops the hope for superior exploration of FeIIIOH NPs/NF toward the expansion of real and large‐scale hydrogen production with the lowest price.

The development and production of non-noble metal electrocatalysts with exceptional activity and stability for water electrolysis was essential for energy conversion and storage. An optimized working electrode of core-shell nanosphere Fe 2 Co 8 HCF on nickel foam exhibits a small overpotential of 241 mV (63 mV/dec) for OER and 158 mV (92 mV/dec) for HER at 10 mA/cm 2 (without iR correction) in 1.0 M KOH. Fe 2 Co 8 HCF shows ultra-stability (150 h) with loss of 2.9 % and 3.1 % for OER and HER, respectively. The interaction between Fe, Co and HCF that resulted in the formation of core-shell nanostructure was highly beneficial for reaction kinetics. The active bifunctional Fe 2 Co 8 HCF/NF electrode pair aids in the development of a water electrolyzer that provides 10 mA/cm 2 at 1.63 V. The Fe 2 Co 8 HCF/NF//Fe 2 Co 8 HCF/NF displays great durability (over 150 h) with loss of 4.2 %. The solar-driven water electrolysis at 1.63 V demonstrates the enhanced efficiency of an optimized electrocatalyst. These results imply that Fe 2 Co 8 HCF/NF// Fe 2 Co 8 HCF/NF can be utilized to generate a huge amount of hydrogen at low cost.

The oxygen (OER) evolution reaction plays a crucial role for storage of renewable energy sources but, active sites of the active electrocatalysis remain in challengeable. In this work, we have developed sulfonated polyaniline (SPANI) coordinated with Co sites to investigate the OER process. To improve the electrical conductivity and electrocatalytic efficiency towards OER herein, we report Co@SPANI synthesized by solvothermal method. The different physical characterization (SEM, TEM, XRD, IR, XPS and UV‐DRS) and electrochemical methods (voltammetry, chronopotentiometry and EIS) have been used to characterize Co@SPANI materials and examined the correlation of materials with activity. The cobalt doped SPANI (Co@SPANI‐800) exhibits higher electrocatalytic activity, showing smaller Tafel slope of 167 mV dec−1 with lower overpotential of 312 mV at 10 mA cm−2 in 1 M KOH, which reveal that abundant Co‐metal sites remarkably supporting the OER activity. Co@SPANI‐800 exhibits exceptional OER performances and durability over 200 h with loss of <3.5 % in alkaline medium. At 1.54 V, solar powered water electrolysis confirmed the effectiveness of newborn electrocatalyst in solar energy to hydrogen energy conversion. Therefore, this work offered new path for designing materials as self‐supporting electrode for water splitting and for other potential applications.