Abstract
A unique three-dimensional (3D) structure consisting of a hierarchical nickel–cobalt dichalcogenide spinel nanostructure is investigated for its electrocatalytic properties at benign neutral and alkaline pH and applied as an air cathode for practical zinc–air batteries. The results show a high oxygen evolution reaction catalytic activity of nickel–cobalt sulfide nanosheet arrays grown on carbon cloth (NiCo2S4 NS/CC) over the commercial benchmarking catalyst under both pH conditions. In particular, the NiCo2S4 NS/CC air cathode shows high discharge capacity, a narrow potential gap between discharge and charge, and superior cycle durability with reversibility, which exceeds that of commercial precious metal-based electrodes. The excellent performance of NiCo2S4 NS/CC in water electrolyzers and zinc–air batteries is mainly due to highly exposed electroactive sites with a rough surface, morphology-based advantages of nanosheet arrays, good adhesion between NiCo2S4 and the conducting carbon cloth, and the active layer formed of nickel–cobalt (oxy)hydroxides during water splitting. These results suggest that NiCo2S4 NS/CC could be a promising candidate as an efficient electrode for high-performance water electrolyzers and rechargeable zinc–air batteries.
Highlights
Splitting water into pure hydrogen and oxygen to generate sustainable green hydrogen energy has been intensively studied in recent years, which can replace fossil fuel use.[1,2] the efficiency of water splitting has so far been limited by the lack of sustainable catalysts toward the oxygen evolution reaction (OER) that can accelerate the kinetics.[3−5] So far, IrOx and RuO2 are the best-known OER catalysts, their high cost and scarcity limit their widespread use.[4]
On the basis of our knowledge, we describe the physical and electrochemical properties of NiCo2S4 NS/carbon cloth (CC) as a highly active OER catalyst in both neutral and alkaline media, which have not been thoroughly investigated so far
The anion exchange reaction from Co32−/OH− anions to S2− anions occurred at 160 °C for 6 h, thereby leading the complete phase transformation from cobalt−nickel carbonate hydroxide hydrate to nickel−cobalt sulfide on the CC
Summary
Splitting water into pure hydrogen and oxygen to generate sustainable green hydrogen energy has been intensively studied in recent years, which can replace fossil fuel use.[1,2] the efficiency of water splitting has so far been limited by the lack of sustainable catalysts toward the oxygen evolution reaction (OER) that can accelerate the kinetics.[3−5] So far, IrOx and RuO2 are the best-known OER catalysts, their high cost and scarcity limit their widespread use.[4]. It is highly required to develop efficient OER electrocatalysts that can operate in both alkaline and neutral media for overall water splitting even though it is relatively tough searching for those catalysts
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