Nickel-Doped Cobalt Oxyhydroxide Nanowires Coupled Polyaniline Functionalizedcarbon Cloths As Multifunctional Electrocatalysts for Hydrogen/Oxygen Evolutionreactions at All pH Levels

Abstract

Hydrogen represents a carbon-free and sustainable energy carrier. Electrochemical water splitting via hydrogenevolution reaction (HER) and oxygen evolution reaction (OER) is a green approach for the hydrogen production.Nevertheless, unfavorable thermodynamics and sluggish kinetics limit the water splitting efficiency. While thebenchmark catalysts such as Pt@C and RuO2/C catalysts display remarkable catalytic activity, the inferiordurability remains a major concern. Further, scarcity and high demand result in sharp rise in cost, hindering theirlarge-scale commercialization. Herein we rationally design the synthesis of nickel-doped cobalt oxyhydroxidenanowires grown on PANi functionalized CF (Ni@CoOOH@PANi-CF) as multi-functional electrocatalyst for HERand OER. In this design, the interfacial PANi layers substantially improve the surface functionality of the CFsubstrate and thereby facilitates strong coupling interaction with the Ni@CoOOH catalyst, which influences thecharge transport kinetics across the catalyst/substrate interface and also maintains the structural integrity of theoverall catalyst throughout the cyclic and long-term durability tests. Furthermore, the Ni@CoOOH provideabundant active sites for the dissociation of water, while the PANi-CF facilitates the adsorption of H+ ions fromthe intermediates and promotes its convention to hydrogen molecules, which accelerates the HER effectively.Due to these intriguing features, the Ni@CoOOH@PANi-CF manifested remarkable HER efficiency with lowoverpotential (35, 30, and 100 mV mV at 10 mA cm-2) in acidic, alkaline, and neutral electrolytes. Besides, theNi@CoOOH@PANi-CF demonstrated batter durability even in acidic electrolyte. As a key functionality, PANilayers protected the carbon surface from corrosive reactions and suppressed the active catalyst dissolution,resulting in high tolerance for both HER and OER at all pH conditions.