An electrochemically reversible lattice with redox active A-sites of double perovskite oxide nanosheets to reinforce oxygen electrocatalysis

Abstract

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...

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

“…PBMNC NS samples were synthesized following the ubiquitous glycine‐nitrate sol‐gel synthesis method (Scheme 1 and experimental section, supporting information) [13] . In this two‐step protocol, single perovskite oxide is obtained by calcination of a gelled residue at 950 °C for 5 h in air followed by an optimized 30 h reduction under controlled H 2 atmosphere to obtain the double perovskite oxide (PBMNC‐ x ) phase.…”

“…Elemental compositions of the final products were ascertained by energy‐dispersive X‐ray spectroscopic (EDS) analysis. Rietveld refined powder X‐ray diffraction (PXRD) patterns help in elucidating the crystal structures and unit cell parameters whereby a mixed cubic ( Pm3̅m ) and hexagonal ( P6 3 /mmc ) phase of the single perovskite is found to transform into the tetragonal ( P4/mmm ) phase of PBMNC‐ x after thermal reduction (Figure 1a, Figure S1, Figure S2 and Table S1) [13] . The PXRD patterns of PBMNC‐ x NSs with tetragonal crystal structure have three additional reflections.…”

“…The PXRD patterns of PBMNC‐ x NSs with tetragonal crystal structure have three additional reflections. The reflections at 2θ ∼24° and 44° correspond to BaCO 3 and metallic Co impurity phases, respectively (Figure 1a), [13,32] and the peak at 2θ ∼31.5° is due to another tetragonal ( P4/mmm ) phase of the electrochemically inactive Ba 3 Nb 5 O 12 (Table S1) [33] . Although these impurities are the result of Nb‐doping and high temperature reduction, this averse effect is overhauled by the added benefits of a favourable electronic environment at the Nb‐doped B‐site and the resultant 2D architecture [13,32] …”

“…This is in accordance with the slight increase in unit cell volume consistently from PBMNC‐0.1 to PBMNC‐0.3 (Table S1), although there is an initial decrease in unit cell volume from PBMNC‐0.0 to PBMNC‐0.1 due to a smaller radius of Nb 5+ (78 pm) substituting the slightly larger Mn 3+ cation of radius 78.5 pm. Perovskite oxide electrocatalysts require a perfect balance of cations and anions in the lattice since O 2 binding always depends on an optimized oxygen non‐stoichiometry [13] …”

“…The family of (ABO 3‐δ ) n (A=rare or alkaline earth metal ion, B=transition metal ion, δ=oxygen non‐stoichiometry) type double perovskite oxides ( n =2) asserts many advantages over other counterparts [12] . Our group recently explored double perovskite oxide NSs having an electrochemically reversible lattice to boost the bifunctional activity [13] . However the oxygen‐deficient double perovskite oxide having semi‐metallic characteristics impedes charge percolation and therefore conductive scaffolds of sp 2 hybridized carbon nanomaterials are used to circumvent this impediment [14–16] .…”