Tuning the Polarity of a Fibrous Poly(vinylidene fluoride-co-hexafluoropropylene)-Based Support for Efficient Water Electrolysis

Abstract

Water electrolysis under alkaline conditions is of interest due to the applicability of non-precious metal-based materials for electrocatalysts. However, the successful design and synthesis of earth-abundant and efficient catalysts for the oxygen evolution reaction (OER) remain a significant challenge. This work presents cost-effective and straightforward ways to improve the OER activity under alkaline conditions by activating the catalyst–support and reactant–support interaction. Micro/nano-sized fibrous poly(vinylidene fluoride- co -hexafluoropropylene) (PVdF-HFP) was synthesized via simple and scalable electrospinning and subsequently coated with Cu by electroless deposition to obtain the electrocatalyst with a large specific surface area, enhanced mass transport, and high catalyst utilization. Scanning electron microscopy, infrared spectroscopy, and X-ray diffraction confirmed the successful synthesis of the series of Cu/PVdF-HFP fibrous catalysts with varied ferroelectric polarizability of the PVdF-HFP support in the order of stretch-anneal > anneal > stretch > without pre-treatment of the catalyst. The best OER activity was confirmed for the Cu/PVdF-HFP catalyst with stretch and annealed treatment among the catalysts tested, suggesting that both the reaction kinetics and energetics of stretch-annealed Cu/PVdF-HFP catalysts were optimal for the OER. The electron delocalization between Cu and PVdF-HFP substrates (electron transfer from Cu to the negatively charged (δ – eff ) PVdF-HFP region at the Cu|PVdF-HFP interface) and the enhanced transport of reactive hydroxide species and/or the increase in the local pH by positively charged (δ + eff ) PVdF-HFP region concertedly accelerate the OER activity. The overall activity for the prototype water electrolyzer increased 10-fold with stretch-anneal treatment compared to the one without pre-treatment, highlighting the effect of tuning the catalyst–support and reactant–support interaction on improving the efficiency of the water electrolysis.

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“…55 He analyzed electrochemical reaction processes at the electrode interface, which resulted in the development of highly active electrocatalysts. [56][57][58][59] Another awardee, Kimura is currently an assistant professor of Tohoku University. He received his PhD of environmental science from Tohoku University in 2015.…”

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