Synergistically Enhanced Oxygen Evolution Reaction Catalysis for Multielement Transition-Metal Oxides

Abstract

Transition metal oxides have been extensively investigated as novel catalysts for oxygen evolution reaction (OER). Partial elemental substitutions are effective ways to increase catalytic performance and such electronic interactions between multiple elements are known as synergistic effects. However, serious issues such as random atomic arrangement and ambiguous roles of constituent elements humper theoretical investigations for rational materials design. Herein, we describe systematic study on OER activity of AA′ 3 B 4 O 12 -type quadruple perovskite oxides, in which multiple transition metal ions are located at distinct crystallographic sites. Electrochemical measurements demonstrate that OER catalytic activities of quadruple perovskite oxide series, CaCu 3 B 4 O 12 (B = Ti, V, Cr, Mn, Fe, and Co), are all superior to those of simple perovskite counterparts CaBO 3 . The order of activity of B-site transition metal ions for CaBO 3 (Fe 4+ > Co 4+ ≫ Ti 4+ , V 4+ , Cr 4+ , Mn 4+ ) is retained in CaCu 3 B 4 O 12 , indicating that B-site ions play a primary role whereas A′-site Cu ions secondarily contribute to OER activity for CaCu 3 B 4 O 12 . Charge-transfer energies, energy differences between oxygen 2p band center and unoccupied 3d band center of B-site transition metal obtained from first-principles electronic-state calculations, illustrate that OER overpotentials of quadruple perovskite oxides are lower than simple perovskite oxides by ∼150 mV. These findings propose a simple avenue to realize enhanced OER activity for multiple transition-metal ions.

Atomic-scale perturbation of oxygen octahedra via surface ion exchange in perovskite nickelates boosts water oxidation

“…Although various factors are involved in oxygen electrocatalysis performance, the charge transfer between transition metals and oxygen appears to be one of the more critical steps. Indeed, as rate-limiting reactions with large activation barriers are usually involved in the formation of intermediate adsorbates of OH* and O* during the OER, facilitating the transfer of electrons between transition metals and adsorbates via oxygen is an important issue 18,25,54,55 . The charge transfer from transition metals to adsorbates via oxygen (e.g., Ni 3+ -O(OH*) − → Ni 4+ -OO* 2− ) would be much easier and more likely to occur if a larger number of density of O 2 p and metal 3 d bonding states were placed near the Fermi level rather than far below it.…”

Systematic Study of Descriptors for Oxygen Evolution Reaction Catalysis in Perovskite Oxides

“…OER catalytic activities were evaluated by using rotating disk electrode system in the same manner as the previous study. 20,25,26 A 5 wt% proton-type Nafion suspension (Sigma-Aldrich),…”

“…The oxygen 2p band centers and unoccupied 3d band centers of transition metal atoms were computed from the projected density of states (DOS). 20 Oxygen 2p band center (ε 2p ) 18 was obtained by eq. 1 as:…”

“…Recently, Hong et al 19 proposed that charge-transfer energy determined by X-ray spectroscopy experiments serves as an electronic descriptor to explain change in OER mechanism, followed by examination for selected perovskite oxides very recently. 12,20 Although the above descriptors are all focused on the metal-oxygen covalency to increase charge-transfer in rate-determining step of OER and applicable even for other systems, 21,22 careful verification of universality and scope of application among a wide range of compounds is desired.…”

A bifunctional perovskite oxide catalyst: The triggered oxygen reduction/evolution electrocatalysis by moderated Mn-Ni co-doping

“…For example, ORR wieldy exists in fuel cells and the discharge process of metal-air batteries [7,8], while OER is involved in electrolytic water splitting and metal-air batteries during the charge process [9,10]. However, the state-of-the-art noble metal (oxide) electrocatalysts, such as Pt-based materials for ORR and Ir-and Ru-based materials for OER, are significantly limited by the high cost, scarce resource, and low bifunctional activity [11]. Therefore, in order to address these challenges, the develop-ment and rational design of advanced bifunctional non-noble metal ORR/OER catalysts are particularly attractive [12,13].…”