Highly Efficient Perovskite‐Based Electrocatalysts for Water Oxidation in Acidic Environments: A Mini Review

Abstract

has received considerable attention as a promising energy storage media owing to its high gravimetric energy density (142 MJ kg −1 ) and near-zero carbon emission power generation. [7][8][9][10][11][12] Currently, both alkaline and protonconducting polymer electrolyte membrane water electrolysis (PEMWE), also known as proton exchange membrane water electrolysis, are well established as commercial or near-commercial electrochemical water-splitting technologies. [13,14] Compared to alkaline water electrolysis, PEMWE has the advantages of faster dynamics owing to high ionic conductivity, operation at higher current density (maximum 2-3 A cm −2 ), and high-purity H 2 production. [15,16] However, PEMWE necessitates the use of noble-metal-based electrocatalysts on both cathode and anode. Various kinds of electrocatalysts have been developed to replace platinum/ carbon (Pt/C) for the hydrogen evolution reaction (HER) at the cathode. [17][18][19][20][21] However, currently available electrocatalysts for the oxygen evolution reaction (OER) at the anode still depend on iridium (Ir), ruthenium (Ru), or their oxide forms. The high cost and scarcity of Ir and Ru limit the large-scale application of PEMWE. [22,23] Although some noblemetal-free materials show OER activity in strongly acidic solutions, many of them are still unstable in acidic solutions and exhibit inferior electrocatalytic OER activity than noble-metalbased materials. [24,25] Furthermore, especially in acidic media, oxygen evolution is even more limited in the water-splitting process owing to the slow kinetics of water oxidation originating from the complex four-proton-coupled electron transfer reactions as well as additional water dissociation processes. [26][27][28] As such, it is mandatory to develop noble-metal-reduced OER electrocatalysts with a high electrocatalytic activity that are well tolerated in acidic solutions. Some OER electrocatalysts which could be tolerated in acidic solutions were reported before 2010. However, since 2015, intensive research has been carried out to address the other aforementioned issues by developing alternative electrocatalytic materials for the OER in acidic solutions.Recently, Ir-or Ru-based perovskite oxides have emerged as promising novel OER electrocatalysts in acidic solutions, owing to their multimetal-oxide nature that can reduce the usage of noble metal. Perovskite oxides have various structures, i.e., single perovskite structure with the general formula ABO 3 , double perovskite structure with the formula A 2 BB′O 6 (double Proton-conducting polymer electrolyte membrane water electrolysis (PEMWE) is a promising technology for generating clean and sustainable hydrogen fuels from water. However, PEMWE requires the use of expensive electrocatalysts; the currently available electrocatalysts for the oxygen evolution reaction (OER) depend on noble metals (Ir, Ru). Since noble metals are expensive, commercialization of PEMWE remains elusive. In addition, PEMWE suffers from the very slow kinetics of the OER in acidic medi...

Novel engineering of ruthenium‐based electrocatalysts for acidic water oxidation: A mini review

“…The structure of perovskite oxides could be generally divided as follows (Figure 6(A)): single perovskite structure (ABO 3 ), double perovskite structure (A 2 BB'O 6 ) and layered perovskite structure (A n+1 B n O 3n+1 , n stands for the number of octahedral layers in perovskite‐like stack) 18 . The A‐site is occupied by an alkaline/a rare‐earth metal or a combination of the two (Sr, Ba, La, Pr, etc.)…”

“…Recently, perovskite oxides with B‐sites substituted by Ir 105–108 or Ru have been considered as one type of promising electrocatalysts for OER in acidic electrolyte. Compared with Ir‐based perovskite oxides, 18 B sites substituted with Ru in perovskite oxides have been rarely studied and reviewed as electrocatalysts for acidic water oxidation. Thus, in this study the recent advances of Ru‐based perovskite oxides are discussed.…”

“…(A) The typical crystal structure of single (ABO 3 ), B‐double (A 2 BB'O 6 ), and layered (A n +1 B n O 3 n +1 ) perovskite oxides. (A) Reproduced from Reference 18 with permission from Wiley‐VCH. (B) The plot of negative theoretical overpotential for perovskite oxides against free energy difference of the ΔG 0 O* − G 0 HO* step.…”

“…The cost of Ru is at least six times cheaper than that of Ir, indicating Ru and RuO 2 may deserve a more promising candidate for PEMWEs 17 . Further, Ru‐based perovskite/pyrochlore oxides also have attracted much interest for their OER performance 18 …”

Nano-Sized Double Perovskite Oxide as Bifunctional Oxygen Electrocatalysts

“…Among them, perovskite oxide, especially double perovskite oxide, has been extensively studied due to their earth-abundant nature and intrinsically high catalytic activity [9][10][11]. The flexible compositional structure of perovskite oxide makes its wide potential to be tuned as superior catalysts [12][13][14][15].…”