2D Heterojunction Between Double Perovskite Oxide Nanosheet and Layered Double Hydroxide to Promote Rechargeable Zinc-Air Battery Performance

The role of two-dimensional (2D) materials in electrocatalytic energy conversion reactions is unprecedented among which the earth-abundant metal oxide nanosheets (NSs) that could promote bifunctional electrocatalytic oxygen reduction and evolution reactions (ORR/OER) remain elusive. <20 nm thick double perovskite oxide, Pr0.5Ba0.5Mn1.8-xNbxCo0.2O6-delta(PBMNC-x, x=0-0.3, delta=0.38-0.59) NSs having a lateral spread of similar to 300 nm were designed with exsolved metallic Co and Co3O4 nanoparticles (NPs) anchored to the NS surface. PBMNC-0.1 NSs demonstrate the best ORR/OER bifunctional activity among all PBMNC-x samples with a bifunctionality index (BI) of 1.36 V, which is the combined OER and ORR overpotential (eta) at 10 and-3 mA/cm(2) current density, respectively. To promote the OER performance, chemically attached 2D heterojunctions of PBMNC-0.1 NS and ymol % of NiFe (3 : 1) layered double hydroxide (NiFe-LDH) were hydrothermally synthesized. Among the PBMNC/LDH-y heterojunctions, PBMNC/LDH-20 shows the lowest BI of 1.06 V because of an electronic reorganization at the heterojunction as evidenced from Mott-Schottky analysis. Proof of concept rechargeable zinc-air battery (r-ZAB) with PBMNC/LDH-20 cathode exhibits a specific capacity of 695.6 mA.h/g(Zn) and roundtrip charge-discharge stability for 100 h at 5 mA/cm(2), surpassing the performance of state-of-the-art Pt/C-RuO2 couple.