Surface Interrogation of Electrodeposited MnO_x and CaMnO₃ Perovskites by Scanning Electrochemical Microscopy: Probing Active Sites and Kinetics for the Oxygen Evolution Reaction

Abstract

Surface interrogation scanning electrochemical microscopy (SI‐SECM) of two electrodeposited manganese‐based electrocatalysts, amorphous MnOx and perovskite CaMnO3, was used to investigate the manganese oxidation state relating to the oxygen evolution reaction (OER) under neutral conditions. The results indicate the amounts of MnIII and MnIV species in MnOx and CaMnO3 depend on potential. A MnV species was identified in both structures during the OER. Time‐delay titration of MnV further revealed that MnOx produced two types of active sites with different OER reaction rates: k′fast(MnOx)=1.21 s−1 and k’slow(MnOx)=0.24 s−1. In contrast, CaMnO3 perovskites in which the MnV species formed at a less positive potential than that in MnOx, displayed only one kinetic behavior with a faster reaction rate of 1.72 s−1.

An Intermetallic CaFe6Ge6 Approach to Unprecedented Ca−Fe−O Electrocatalyst for Efficient Alkaline Oxygen Evolution Reaction

“…Intriguingly, several works on Ca-containing TM-oxido compounds have emphasized the significant role of Ca in promoting photochemical water oxidation, particularly its binding and activation effect towards H 2 O molecules. [12][13][14] Nonetheless, to the best of our knowledge, such compounds have been hardly explored for electrocatalytic OER in an alkaline environment. Aiming at this condition, only a very limited amount of Cacontaining Mn-based oxides and some perovskite-type TM oxides [15][16][17][18] have been studied, which show low catalytic efficiency.…”

“…Nevertheless, the role of redox‐inactive alkaline earth metals for electrocatalytic water oxidation has long been underestimated. Intriguingly, several works on Ca‐containing TM‐oxido compounds have emphasized the significant role of Ca in promoting photochemical water oxidation, particularly its binding and activation effect towards H 2 O molecules [12–14] . Nonetheless, to the best of our knowledge, such compounds have been hardly explored for electrocatalytic OER in an alkaline environment.…”

Interconnecting 3D Conductive Networks with Nanostructured Iron/Iron Oxide Enables a High-Performance Flexible Battery

“…Great efforts have been devoted so far to improve the electrochemical properties of Fe 2 O 3 through electronic structure regulation and introduction of conductive additives. Many strategies, including doping, defect, surface, and size engineering, are available that can effectively optimize the intrinsic and apparent carrier density of transition-metal oxides to improve the electrochemical behavior, particularly the redox properties. ,− Additionally, another effective method to increase the conductivity of Fe 2 O 3 is to disperse it with carbon. − Yet, optimizing the available strategies to design a highly efficient Fe-based anode for the Ni/Fe battery remains elusive. Particularly, few previous studies have provided a fundamental insight into the intrinsic behavior that alters the charge storage ability.…”

Multidimensional Dual-Carbon Skeleton Network Confined MnOx Anode Boosting High-Performance Lithium-Ion Hybrid Capacitors

“…24 Another direction is adjusting the phase composition of manganese oxide to enhance intrinsic conductivity and increase electrochemically active sites in the process of fabricating MnO x . 25,26 Yan et al used a freeze-drying easy-going annealing process to prepare a pure phase MnO and carbon composite, which has good lithium storage capacity. 27 Regrettably, in the existing research, most of these strategies are not suitable to solve the problem simply and effectively.…”

“…Moreover, the introduction of heteroatoms provides abundant active sites for porous carbon, enhancing the electronic conductivity and wettability of the material surface. − In addition, the combination of the noncarbon structure of MnO x nanoparticles and carbon materials produces a synergistic effect to improve the lithium storage performance . Another direction is adjusting the phase composition of manganese oxide to enhance intrinsic conductivity and increase electrochemically active sites in the process of fabricating MnO x . , Yan et al used a freeze-drying easy-going annealing process to prepare a pure phase MnO and carbon composite, which has good lithium storage capacity . Regrettably, in the existing research, most of these strategies are not suitable to solve the problem simply and effectively.…”