Entwined Co(OH)₂ In Situ Anchoring on 3D Nickel Foam with Phenomenal Bifunctional Activity in Overall Water Splitting

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–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.

Green synthesis of fusiform-shaped Fe-PANI as a phenomenal dual electrocatalyst for overall water splitting and assessment of its sustainability standards

“…Measurements in 1.0 M KOH were conducted to analyze the electrocatalytic activity of Fe-PANI/NF and Pt/C/NF for the HER. 43,60 The Fe-PANI/NF polarization curve showed the lowest overpotential of 155 mV in comparison to that of NF (320 mV) and was near to that of the Pt/C/NF electrocatalyst (5% Pt on carbon) (36 mV) at 10 mA cm À2 (Fig. 15).…”

Ultrafine Core‐Shell Nanostructured Iron Cobalt Ferrocyanide with Excellent Electrocatalytic Activity toward Overall Water Splitting

“…As a result, the core‐shell nanosphere electrocatalyst might be a promising option for electrochemical energy conversion [35,36] . The HER operation, which utilizes the Tafel‐Volmer‐Heyrosky mechanism, generates H 2 from transition metal chalcogenides [80,81] . The increased HER activity of Fe 2 Co 8 HCF might be explained by Volmer‐Heyrovsky step, which facilitates H 2 evolution at lower overpotential in 1 M KOH.…”

“…[35,36] The HER operation, which utilizes the Tafel-Volmer-Heyrosky mechanism, generates H 2 from transition metal chalcogenides. [80,81] The increased HER activity of Fe 2 Co 8 HCF might be explained by Volmer-Heyrovsky step, which facilitates H 2 evolution at lower overpotential in 1 M KOH. 2M cat H chem ⇋H 2 " + M cat (Tafel);…”

Regulated Bimetal-Doped Polyaniline: Amorphous-Crumple-Structured Viable Electrocatalyst for an Efficient Oxygen Evolution Reaction

“…Cobalt has excellent electrical conductivity and more active sites, which increased the electrocatalytic activity. 35 Nickel-contained electrocatalysts display excellent corrosion resistance in aqueous alkaline media. 34 The scanning electron microscopy (SEM) image displays the particle distribution of different sizes and shapes of the Co 4 Ni 1 @PANI electrocatalyst, implying the rugged morphology.…”

“…Cobalt–nickel-doped polyaniline (CoNi@PANI) was solvothermally synthesized using glucose as a green reducing agent at 130 °C for 12 h. − Formulated amorphous CoNi@PANI exhibits an excessive electrocatalytic active surface area with high activity and conductivity and prolonged stability. Cobalt has excellent electrical conductivity and more active sites, which increased the electrocatalytic activity . Nickel-contained electrocatalysts display excellent corrosion resistance in aqueous alkaline media .…”