posted on 2024-01-19, 20:11authored byXin Wang, Harish Singh, Manashi Nath, Kurt Lagemann, Katharine Page
Hastening the progress
of rechargeable metal–air batteries
and hydrogen fuel cells necessitates the advancement of economically
feasible, earth-abundant, inexpensive, and efficient electrocatalysts
facilitating both the oxygen evolution reaction (OER) and oxygen reduction
reaction (ORR). Herein, a recently reported family of nano (5A1/5)Co2O4 (A = combinations of transition
metals, Mg, Mn, Fe, Ni, Cu, and Zn) compositionally complex oxides
(CCOs) [Wang et al., Chemistry of Materials, 2023,35 (17), 7283–7291.] are studied
as bifunctional OER and ORR electrocatalysts. Among the different
low-temperature soft-templating samples, those subjected to 600 °C
postannealing heat treatment exhibit superior performance in alkaline
media. One specific composition (Mn0.2Fe0.2Ni0.2Cu0.2Zn0.2)Co2O4 exhibited an exceptional overpotential (260 mV at 10 mA cm–2) for the OER, a favorable Tafel slope of 68 mV dec–1, excellent onset potential (0.9 V) for the ORR, and lower than 6%
H2O2 yields over a potential range of 0.2 to
0.8 V vs the reversible hydrogen electrode. Furthermore, this catalyst
displayed stability over a 22 h chronoamperometry measurement, as
confirmed by X-ray photoelectron spectroscopy analysis. Considering
the outstanding performance, the low cost and scalability of the synthesis
method, and the demonstrated tunability through chemical substitutions
and processing variables, CCO ACo2O4 spinel
oxides are highly promising candidates for future sustainable electrocatalytic
applications.