Porous Mn₂O₃: A Low‐Cost Electrocatalyst for Oxygen Reduction Reaction in Alkaline Media with Comparable Activity to Pt/C

Abstract

Preparing nonprecious metal catalysts with high activity in the oxygen reduction reaction (ORR) can promote the development of energy conversion devices. Support-free porous Mn2 O3 was synthesized by a facile aerosol-spray-assisted approach (ASAA) and subsequent thermal treatment, and exhibited ORR activity that is comparable to commercial Pt/C The catalyst also exhibits notably higher activity than other Mn-based oxides, such as Mn3 O4 and MnO2 . The rotating ring disk electrode (RRDE) study indicates a typical 4-electron ORR pathway on Mn2 O3 . Furthermore, the porous Mn2 O3 demonstrates considerable stability and a good methanol tolerance in alkaline media. In light of the low cost and high earth abundance of Mn, the highly active Mn2 O3 is a promising candidate to be used as a cathode material in metal-air batteries and alkaline fuel cells.

Atomic Layers of MoO2 with Exposed High‐Energy (010) Facets for Efficient Oxygen Reduction

“…Remarkably, the electron transfer number of MoO 2 ‐G‐20 h is as high as 3.94 (Figure d), same to the Pt/C catalyst, suggesting that oxygen is reduced predominantly through a direct four‐electron pathway. Moreover, in the case of MoO 2 ‐G‐20 h, a high kinetic current density of 8.47 mA cm −2 is achieved, which is much higher than those of other MoO 2 ‐G samples (3.94–7.93 mA cm −2 ), even higher than the most reported transition metal oxide (cobalt oxide, manganese oxide)/carbon composites (3.0–8.0 mA cm −2 ) for ORR (Figure d and Figure S20, Supporting Information) . Close inspection reveals that the electrocatalytic activity of MoO 2 ‐G is strongly dependent on the amounts of exposed (010) facets of MoO 2 nanocrystals as shown in Figure S21 (Supporting Information).…”

Mass‐Production of Mesoporous MnCo2O4 Spinels with Manganese(IV)‐ and Cobalt(II)‐Rich Surfaces for Superior Bifunctional Oxygen Electrocatalysis

“…The main reason is that the average Mn valence of these MnCo 2 O 4 catalysts is between Mn II and Mn III , preventing ORR being improved. We are fortunate to have developed a facile spray‐pyrolysis approach for the fabrication of mesoporous Mn 2 O 3 with Pt/C comparable ORR activity via modulating Mn chemical state . Therefore, it is also expectable to achieve the bifunctional performance of MnCo 2 O 4 through surface chemical state engineering.…”

Recent Progress on Transition Metal Oxides as Bifunctional Catalysts for Lithium‐Air and Zinc‐Air Batteries

“…Other Mn oxides also showed excellent catalytic activity. For instance, Mn 2 O 3 expresses a bifunctional activity even better than that observed for MnO 2 and Mn 3 O 4 ,. However, this catalyst exhibits very low stability because it can be easily oxidized .…”