Lamellar-assembled PdNi super-nanosheets as effective oxygen redox dual-electrocatalysts for rechargeable Zn-air batteries

Exploration of bifunctional electrocatalysts toward effective oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)is pivotal for developing high-efficiency and rechargeable metal-air batteries but remains great challenging.Here we elaborately synthesize lamellar-assembled PdNi super-nanosheets(SNSs)with an optimized Pd/Ni molar ratio to serve as attractive ORR and OER bifunctional electrocatalysts for rechargeable high-powered Zn-air batteries(ZABs).The products are layer-by-layer stackings of ultrathin PdNi nanosheet motifs.On the drastically extended two-dimensional(2D)surface,the inserted Ni atoms can substantially lower down the d-band center of surface Pd toward improved ORR kinetics and concurrently create oxytropic NiOx sites to adsorb–OH groups for promoting the reverse OER electrocatalysis.Specifically,the ORR mass activity and specific activity of the primary Pd_(92)Ni_(8)SNSs attain 2.5 A·mg^(−1)and 3.15 mA·cm^(−2),which are respectively 14 and 9 times those of commercial Pt/C.Meanwhile,the OER activity and stability of Pd_(92)Ni_(8)SNSs/C distinctly outperform those of the RuO_(2)benchmark,suggesting excellent reversible oxygen electrocatalysis.The power density of the ZAB with Pd_(92)Ni_(8)SNSs/C as the air cathode is 2.7 times higher than that by Pt/C benchmark.Significantly,it can last for over 150 h without significant performance degradation during the charge–discharge cycle test.This work showcases a feasible strategy for developing self-assembled multimetallic 2D nanomaterials with excellent bifunctional catalytic performances toward energy conversion applications.

IrWOx上吸附的OH^*物种对碱性氢电催化的不同促进作用

碱性氢电极反应过程包括氢氧化反应(HOR)和氢析出反应(HER),改善这两个反应复杂的动力学过程对于实现碱性交换膜燃料电池(AEMFCs)和电解水(AEMWEs)的商业化是非常重要的.但是,它们的反应机理仍旧存在很大的争议性.据此,本文设计合成了一种由无定形的氧化钨团簇修饰的铱钨纳米晶(Ir WOx)材料,在电化学催化碱性HOR和HER的过程中, Ir WOx表现出明显高于商业铂碳催化剂(Pt/C)三倍的性能,具有超高的交换电流密度和质量活性.密度泛函理论(DFT)计算表明,铱钨纳米晶附近的氧化钨团簇对于促进碱性条件下的可逆氢电极反应起着关键性作用,且表现出不同的反应机理,包括HOR的氢结合能(HBE)机理和HER的双功能机理.这项研究工作有望促进研究者们加深对碱性HOR和HER催化机理的认识,为合理设计高效催化碱性HOR和HER的电催化剂提供了新途径.