Electrochemically Controlled Synthesis of Ultrathin Nickel Hydroxide Nanosheets for Electrocatalytic Oxygen Evolution

Abstract

The development of oxygen evolution reaction (OER) catalysts with high activity and high stability through convenient and economical methods is greatly important for the promotion of hydrogen energy based on electrolysis technology. Herein, by using an unconventional high electrodeposition potential, novel petal-like clusters constructed by cross-linking ultrathin nickel hydroxide nanosheets were controllably synthesized on nickel foam (or copper foam or carbon cloth) and the effect of electrodeposition conditions on their OER performance was carefully explored. Due to the abundant catalytically active sites, promoting electron conduction/mass transmission from the specific micro–nano structure, as well as the ultrasmall thickness of ∼3.0 nm, the optimized α-Ni­(OH)2/NF self-supporting electrode exhibits excellent electrocatalytic performance for OER, merely requiring low overpotentials of 192 and 240 mV to yield current densities of 10 and 100 mA cm–2 in 1.0 M KOH, respectively, which surpassed those of all of the reported nickel hydroxide/oxides and the benchmark RuO2. Moreover, α-Ni­(OH)2/NF can drive the high-current density (500–1000 mA cm–2) OER at low overpotentials, meeting the requirements of potential industrial applications.

Boosting Activity and Durability of an Electrodeposited Ni(OH)2 Catalyst Using Carbon Nanotube-Grafted Substrates for the Alkaline Oxygen Evolution Reaction

“…Hydrogen production from water splitting using renewable energies can be one of the efficient storage options. , Electrolytic water splitting includes the oxygen evolution reaction (OER) in the anode and the hydrogen evolution reaction (HER) in the cathode, , where the OER is kinetically unfavorable due to four electrons being needed to form oxygen–oxygen bonding. The role of the OER catalyst is thus essential to lessen the overpotential and fasten the water splitting. − IrO 2 and RuO 2 have shown the highest OER activity in both acidic and alkaline electrolyte solutions, but the noble metal catalysts limit the commercialization due to the scarcity and high cost. − Much research has thus focused on nonprecious metals, including Ni, Fe, Co, and Mo, as the alternatives. − Among them, Ni hydroxides have shown active performance under alkaline OER conditions. − …”

Advances and Challenges in Industrial-Scale Water Oxidation on Layered Double Hydroxides

“…169,181 Fluoride-free approaches include cathodic deposition of nanostructured Ni deposit from the electrolyte containing Ni 2+ salts followed by anodic oxidation. 182 Recently, Wan et al 168 reported anodic oxidation of Ni foam in 1−10 M KOH at 1−3 A cm −2 for 3 h, where metal oxidation and oxygen evolution occur simultaneously to give a nanostructured electrode. Besides, oxidation of Ni mesh support was also observed during the long-term stability test.…”

“…It was recently shown that electrodeposition parameters directly regulate the loading mass of Ni(OH) 2 , which directly influences the catalyst morphology. 182 In this way, the higher catalyst loading can in some cases repress the activity as the electrochemical active surface area decreases due to the thickening of the Ni(OH) 2 sheets. Thick deposits can also force the formation of NiO that passivates the Ni mesh anode.…”

“…Commonly, fluoride is added to the electrolyte solutions to etch the oxide that is formed during anodization at constant potential or during cyclic voltammetry . Controlling the reaction rate between oxidation and dissolution is needed to nanostructure the metal foams. , Fluoride-free approaches include cathodic deposition of nanostructured Ni deposit from the electrolyte containing Ni 2+ salts followed by anodic oxidation . Recently, Wan et al .…”

“…This indicates that Ni mesh support can serve as a pool for in situ formation of NiOOH during OER, virtually prolonging anode lifetime until support fully corrodes. It was recently shown that electrodeposition parameters directly regulate the loading mass of Ni­(OH) 2 , which directly influences the catalyst morphology . In this way, the higher catalyst loading can in some cases repress the activity as the electrochemical active surface area decreases due to the thickening of the Ni­(OH) 2 sheets.…”