Nonstoichiometric Perovskite CaMnO_3−δ for Oxygen Electrocatalysis with High Activity

Abstract

Perovskite oxides offer efficient and cheap electrocatalysts for both oxygen reduction reactions and oxygen evolution reactions (ORR/OER) in diverse oxygen-based electrochemical technologies. In this study, we report a facile strategy to enhance the electrocatalytic activity of CaMnO3 by introducing oxygen defects. The nonstoichiometric CaMnO(3-δ) (0 < δ ≤ 0.5) was prepared through thermal reduction of pristine perovskite microspheres and nanoparticles, which were synthesized from thermal-decomposition of carbonate precursors and the Pechini route, respectively. The as-prepared samples were analyzed by chemical titration, structural refinement, thermogravimetric analysis, and energy spectrometry. In 0.1 M KOH aqueous solution, the nonstoichiometric CaMnO(3-δ) with δ near 0.25 and an average Mn valence close to 3.5 exhibited the highest ORR activity (36.7 A g(-1) at 0.70 V vs RHE, with onset potential of 0.96 V), which is comparable to that of benchmark Pt/C. Density functional theory (DFT) studies and electrical conductivity measurement revealed that the enhanced ORR kinetics is due to facilitated oxygen activation and improved electrical properties. Besides high activity, the nonstoichiometric perovskite oxides showed respectable catalytic stability. Furthermore, the moderate oxygen-defective CaMnO(3-δ) (δ ≈ 0.25) favored the OER because of the improved electrical conductivity. This study makes nonstoichiometric CaMnO(3-δ) a promising active, inexpensive bifunctional catalytic material for reversible ORR and OER.

Perovskite Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

“…The effect of oxygen stoichiometry on ORR activity was studied by Takeda et al [67] for SrFeO 3−δ and SrCoO 3−δ as well as by Du et al [68] for CaMnO 3−δ (Figure 2d). The data of Suntivich et al [22] (B = Mn) and Zhou & Sunarso [69] (B = Ni) was also included as a guide for LaBO 3±δ .…”

“…Due to these complications, the composition at the B-site was not included in Figure 2, but can be found in Figure A1. Trends in catalytic activity towards oxygen reduction with (a) substitution of the B-site (data extracted from references [22,56,57]), (b) composition of the A-site (data extracted from references [63][64][65]), (c) substitution of the A-site (data extracted from reference [66]), and (d) oxygen non-stoichiometry (data extracted from references [22,[67][68][69]). LaMnO3 (open symbols in panel b) was excluded from the trend as it is prone to oxygen non-stoichiometry.…”

AMnO3 (A = Sr, La, Ca, Y) Perovskite Oxides as Oxygen Reduction Electrocatalysts

“…surface segregation [22] and oxygen vacancies [23,24]. In this work, we perform a systematic study of the ORR activity of AMnO 3 particles as a function of the nature of the A-site (Ca, Sr, La and Y).…”

Calcium manganate: A promising candidate as buffer layer for hybrid halide perovskite photovoltaic-thermoelectric systems

“…20 Because of its low cost, nontoxic, chemical and thermal stability, oxidation resistance in the air, it has been comprehensively studied as thermo-electric material, rechargeable batteries materials, oxygen electrocatalysis, catalyst carriers, and so on. [21][22][23][24] In this paper, we discussed the possibility of CMO to serve as the buffer layer in hybrid halide perovskites solar cells.…”