Strategies to Break the Scaling Relation toward Enhanced Oxygen Electrocatalysis

Abstract

The vision of a hydrogen economy relies on efficient utilization and production of hydrogen in a hydrogen fuel cell and a water electrolyzer. In both technologies, the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) account for the most efficiency loss because the reactions on catalytic sites are constrained by adsorption-energy scaling relations involving intermediates of *OOH, *O, and *OH (where * denotes the active site). Therefore, a novel paradigm for catalyst design is required by overcoming or circumventing the adsorption-energy scaling relations. In this Review, the fundamentals of oxygen electrocatalysis, including reaction of the mechanism and origin of the adsorption-energy scaling relationship, are first introduced. Crucial strategies to overcome the scaling relations are then summarized. Finally, future research directions in this area are proposed. This work provides guidelines for the rational design of efficient catalysts for oxygen electrocatalysis beyond the limitation posed by scaling relations.

Understanding and Optimizing Ultra‐Thin Coordination Polymer Derivatives with High Oxygen Evolution Performance

“…For the XPS spectrum of O 2s in NiFe‐LDH (Figure 3e), three main peaks located at 529.68, 531,39, and 532.98 eV, respectively, are assigned to metal‐oxygen bonds, surface hydroxyl groups, and adsorbed water. [ 53–58 ] However, the binding energies in the O2s XPS spectrum of R‐NiFe‐CPs are shifted slightly to higher values and a new peak located at 531.57 eV appears, which can be assigned to oxygen deficiencies. [ 33a,b,56–60 ] The negative shift for Ni and Fe 2p and the positive shift for O 2s are due to strong electronic interactions with electron transfer from anions to cations.…”

“…[ 53–58 ] However, the binding energies in the O2s XPS spectrum of R‐NiFe‐CPs are shifted slightly to higher values and a new peak located at 531.57 eV appears, which can be assigned to oxygen deficiencies. [ 33a,b,56–60 ] The negative shift for Ni and Fe 2p and the positive shift for O 2s are due to strong electronic interactions with electron transfer from anions to cations. [ 29a,b,32,61 ] Overall, the charge regulation by structural deficiencies and distortions in R‐NiFe‐CPs caused electron redistributions, which enhance the electron transfer properties and further improve the OER performance, as will be discussed in the following sections.…”

“…This is mainly due to a strong relationship between ΔG M* and structural deficiencies (Figure 5d), where the energy barriers of different OER intermediates can be modulated by the structural deficiencies. [ 47,58,83 ] Optimal catalysts should have neither too high nor too low adsorption or deprotonation energies, along the lines of Sabatier's principle. [ 53,84–86 ]…”

Universality in Oxygen Evolution Electrocatalysis: High‐Throughput Screening and a Priori Determination of the Rate‐Determining Reaction Step

“…[1,2] While Koper [3] was the first to realize that the scaling relations [4,5] inherently limit the performance of catalysts in the oxygen evolution and reduction reactions, Rossmeisl and co-workers illustrated this finding on the oxygen evolution reaction (OER) over oxide surfaces, a milestone in the theoretical description of OER materials. [6] As a consequence, the thermodynamic framework of scaling relations to construct Volcano relations has been frequently used to screen electrode materials for electrocatalytic key processes, including the OER, [7][8][9] which corresponds to the anodic process in electrolyzers. [10] Despite of the success of this simple notion, critical voices are heard, as the Volcano relation is not capable to reproduce activity trends always correctly.…”

Recent Progress in the Development of Screening Methods to Identify Electrode Materials for the Oxygen Evolution Reaction

“…[30] Hence, the breaking of the linear free-energy relationship between the OH and OOH adsorbates is pursued as a promising strategy to develop catalytic materials beyond the thermodynamic limit. [31][32][33] However, different opinions on this approach can be found in the literature, including the view that breaking the scaling relations does not guarantee enhanced catalytic turnover for electrode materials in the OER. [34] Therefore, it might be useful to expand screening concepts also in other directions.…”