B-site cation exsolution in perovskite oxide (ABO3) catalyst to surface decorated bimetallic nanoparticles facilitates the usually arduous trifunctional electrocatalytic activity towards oxygen reduction and water oxidation cum reduction reactions.

Perovskite oxides have emerged as promising oxygen electrocatalysts for fuel cells and batteries, yet their catalytic activity and long-term stability are under debate because of local surface alterations and instabilities under sustained oxidative potential. Interconnected particles (40 nm) of Ba 0.6 Sr 0.4 Co 0.79 Fe 0.21 O 2.67 (BSCF) are decorated by 10−50 wt % Ni 0.6 Fe 0.4 (OH) x [NiFe] layered double hydroxide (LDH) sheets via polyethylenimine linkage. This composite renders modulation of surface charges through Coulombic interaction and provides a leeway for electron mobility between the two components, which bestows relief to the BSCF surface from oxidative degradation. NiFe-LDH (25 wt %) bound to BSCF (BSCF/NiFe-25) is found to be the optimized bifunctional composite after considering the total overpotential of oxygen evolution and reduction reactions. With BSCF/NiFe-25 at the air electrode of a prototyperechargeable Zn−air battery, a low discharge−charge voltage gap (1.16 V at 10 mA cm −2 ), unaltered cyclic stability over 100 h, and an energy density of 776.3 mW•h•g Zn −1 are achieved. BSCF/NiFe-25 outperforms BSCF and is comparable to 20% Pt/C− RuO 2 cathodes in all the standard figures of merit. Our work presents a general strategy to circumvent the reconstructions of perovskite oxide surface under oxidative potentials, by creating highly active, stable, and inexpensive bifunctional composite electrocatalysts for future electrochemical energy storage and conversion devices.

The catalyst surface undergoes reversible structural changes while influencing the rate of redox reaction, the atomistic structural details of which are often overlooked when the key focus is to enhance...

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‐δ(PBMNC‐x, x=0–0.3, δ=0.38–0.59) NSs having a lateral spread of ∼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 (η) at 10 and−3 mA/cm2 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/gZn and roundtrip charge‐discharge stability for 100 h at 5 mA/cm2, surpassing the performance of state‐of‐the‐art Pt/C‐RuO2 couple.

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