PNNL

Abstract

Changes in the local atomic arrangement in crystal caused by the lattice-mismatch-induced strain can efficiently regulate the performance of zinc-air batteries (ZABs) electrocatalysts in many manners, mainly due to modulated electronic structure configurations that affect the adsorption energies for oxygen-intermediates formed during oxygen reduction and evolution reactions (ORR and OER). However, the application of strain engineering in electrocatalysis has been frustrated by strain relaxation caused by structural instability such as dissolution and destruction, leading to insufficient durability towards ORR/OER. Herein, we propose a doping strategy to modulate the phase transition and formation of self-supported cobalt fluoride-sulfide (CoFS) nanoporous films using a low amount of copper (Cu) as a dopant. Such a well-defined Cu-CoFS heterostructure overcomes the obstacle of structural instability. Our study of the proposed Cu-CoFS also helps establish the structure-property relationship of strained electrocatalysts by unraveling the role of local strain in regulating the catalyst electronic structure. As a proof-of-concept, the Cu-CoFS electrocatalyst with doping-modulated strain exhibited superior onset potentials of 0.91 V and 1.49 V for ORR and OER, respectively, surpassing commercial Pt/C@RuO2 and benchmarking non-platinum group metals (non-PGMs) catalysts. The ZABs with Cu-CoFS catalyst delivered an excellent charge/discharge cycling performance with extremly low voltage gap of 0.5 V at the current density of 10 mA cm-2 and successively 0.93 V under high current density 100 mA cm-2 around 500 h and afforded an outstanding peak power density of 255 mW cm-2.