Cation Deficiency Tuning of LaCoO₃ Perovskite as Bifunctional Oxygen Electrocatalyst

Abstract

Oxygen electrocatalysis, including both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), dominates the performance of various electrochemical energy conversion and storage systems. However, the practical applications of these devices are limited as a result of the sluggish kinetics of OER and ORR as well as the high cost and instability of the state-of-the-art noble metal catalyst used in these systems. In this study, cation deficiency is introduced to the A-site of perovskite LaCoO 3 synthesized via polymer-assisted approach to enhance the electrocatalytic activity of both OER and ORR, leading to the boosted bifunctionality of the resultant electrocatalysts, which might be attributed to oxygen vacancy introduction in perovskites. The bifunctionality of the A-site deficiency perovskite (ΔE = 0.948 V) is comparable or even better than the pristine LaCoO 3 (ΔE = 1.063 V) as well as the reported state-of-the-art electrocatalysts, including both perovskites and noble metal electrocatalysts. The stability test also indicates their good stability under alkaline solutions, suggesting that the as-prepared materials can be good candidates as bifunctional electrocatalysts in oxygen-based electrochemical devices, such as fuel cells and metal-air batteries. This work introduces the A-site cation deficiency strategy to improve the bifunctional electrocatalytic performance of perovskites, and highlights the facile polymer-assisted approach for perovskites synthesis.[a] Dr.

Designing High‐Valence Metal Sites for Electrochemical Water Splitting

“…Transition metals, especially earth‐abundant 3d transition metals such as Fe, Co, and Ni, have been extensively exploited as single‐ and multi‐metal electrocatalysts. [ 9e,21b,34 ] First, high‐valence metal sites are constrained in the targeted system of study. For example, there are two types of Co valence states belonging to the two types of geometrical Co ions in spinel cobalt oxide Co 3 O 4 , where two Co 3+ ions reside at the octahedral sites and one Co 2+ ion is at the tetrahedral site.…”

“…First‐principle calculations and experimental studies reveal that non‐3d transition metals, such as Mo, W, Nb, and Sn, usually exist at high‐valence states (Mo 6+ , W 6+ Nb 5+ , and Sn 4+ ). [ 34c,66 ] Therefore, non‐3d transition metals have garnered much attention due to their structurally versatile coordination at their highest oxidation states. Xu et al.…”

“…[ 94 ] In another experimental study, Ni(OH) 2 /NiOOH nanosheets modified by Mo and Fe exhibit an overpotential of ≈280 mV at 10 mA cm −2 and much improved stability at a high current density, confirming the positive doping effect on NiOOH. [ 34c ]…”

“…[ 75a ] Thus, non‐3d transition metals with the highest oxidation state are suitable dopants for 3d transition‐metal‐based perovskite oxides to induce a B‐site ordered structure. [ 34c,66 ] The half‐metallic B‐site ordered double perovskite Sr 2 FeMoO 6 has long been utilized as a conducting ferrimagnet, but its OER performance is poor. [ 212 ] Starting from Sr 2 FeMoO 6 as the host material to provide a short diffusion distance for the different intermediates, a new ordered double perovskite Sr 2 Fe 0.8 Co 0.2 Mo 0.65 Ni 0.35 O 6− δ (SFCMN) has been designed.…”

Infiltrated Ba0.5Sr0.5Co0.8Fe0.2O3-δ-Based Electrodes as Anodes in Solid Oxide Electrolysis Cells

“…Among the most commonly used materials for the electrolyte, fluorite-structured reference electrode (RE)-doped ceria is considered the best candidate to operate SOC at the targeted operative temperatures [14][15][16]. Various oxides with perovskite [17][18][19][20], double perovskite [21][22][23] and Ruddlesden-Popper (RP) [24][25][26] structures showing suitable mixed ionic-electronic conductivity and/or electrocatalytic activity have been proposed for SOFC and SOEC electrode layers.…”