Element strategy of oxygen evolution electrocatalysis based on in situ spectroelectrochemistry

Abstract

Oxygen evolution electrocatalysis has received extensive attention due to its significance in biology, chemistry, and technology. However, it is still unclear how the abundant 3d-elements can be used to drive the four-electron oxidation of water as efficiently as in Nature. In this Feature Article, we will propose a design strategy concerning the optimization of the charge accumulation process based on our ongoing spectroelectrochemical study on Mn, Fe, and Ir oxygen evolution catalysts. Spectroscopic identification of the reaction intermediates showed that the activity of MnO and FeO was dictated by the generation of Mn and Fe, whereas in the case of IrO, the activity did not correlate with the valence change of Ir. The efficiency of charge accumulation through valence change is closely linked with the spin configuration of the metal center, because charge disproportionation, which was found to inhibit charge accumulation in the high-spin 3d metals, requires an electron in the e orbital. In addition to directly increasing the overpotential through the generation of an unstable intermediate, charge disproportionation inhibits charge accumulation by dissipating the total oxidative energy of the system. A favorable charge accumulation process may also be beneficial for electrode kinetics due to the enhanced coupling between reaction rates and electrochemical driving force. The model proposed in this study may help explain why low-spin 4d/5d rare metals are often more active than the abundant high-spin 3d materials for multi-electron transfer reactions in general, and provides new insight into how active 3d-metal catalysts can be synthesized by optimizing the energetics of both bond formation and charge accumulation.

A review of anion-regulated multi-anion transition metal compounds for oxygen evolution electrocatalysis

“…compounds and carbon nanomaterials have been widely investigated as alternatives to precious metal catalysts. 9,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] The OER activity of an electrocatalyst depends on the mass transport from the electrolyte to the catalyst surface, the electrical conductivity of the catalytic material, and the intrinsic activity of the active sites. 29,30 Meanwhile, the intrinsic activity is affected by the interactions between the active sites and the adsorbed oxygencontaining species.…”

Facile Formation of Nanostructured Manganese Oxide Films as High‐Performance Catalysts for the Oxygen Evolution Reaction

“…Notably, this is in agreement with the model established by Nakamura et al. in which Mn 3+ assists in the enhancement of the OER in alkaline media . In addition, the results are also in accord with recent time‐resolved in situ experiments reported by Zaharieva et al.…”

“…derived a new model based on the pH‐dependent activity of MnO 2 OER catalysts . They proposed that in neutral media, Mn 3+ is unstable against charge disproportionation and separates into Mn 2+ and Mn 4+ , and therefore, stabilization of surface‐associated intermediate Mn 3+ species is essential to decrease the overpotential, whereas alkaline media promote the formation of Mn 3+ and facilitate a decrease in the OER overpotentials . Furthermore, numerous Mn‐based materials have been synthesized that suggest the influence of Mn 3+ directly on the OER catalytic activity .…”

Design Strategy of Multi‐electron Transfer Catalysts Based on a Bioinformatic Analysis of Oxygen Evolution and Reduction Enzymes

“…There is currently an intensive interest in energy conversion systems such as fuel cells or solar‐driven water electrolysis cells . Multi‐electron transfer reactions such as the oxygen evolution reaction (OER), or the oxygen reduction reaction (ORR), are indispensable components of these systems, and the development of efficient catalysts has been a central topic in the field of electrocatalysis. So far, in‐silico methods such as the d‐band theory have played a vital role in developing new catalysts ,.…”

“…Extensive databases which contain the genetic sequence of enzymes are readily available online. Furthermore, in contrast to experimentally‐determined activity which deviates depending on the evaluation method (current vs overpotential, or pH conditions),, the unambiguity of the gene sequence allows for a more robust statistical analysis. Despite the enormous potential as a data resource however, no study has previously attempted to utilize genetic sequence information for further catalyst development.…”