Recent Developments of Microenvironment Engineering of Single‐Atom Catalysts for Oxygen Reduction toward Desired Activity and Selectivity

Abstract

Oxygen reduction reaction (ORR) is an essential process for sustainable energy supply and sufficient chemical production in modern society. Singleatom catalysts (SACs) exhibit great potential on maximum atomic efficiency, high ORR activity, and stability, making them attractive candidates for pursuing next-generation catalysts. Despite substantial efforts being made on building diversiform single-atom active sites (SAASs), the performance of the obtained catalysts is still unsatisfactory. Fortunately, microenvironment regulation of SACs provides opportunities to improve activity and selectivity for ORR. In this review, first, ORR mechanism pathways on N-coordinated SAAS, electrochemical evaluation, and characterization of SAAS are displayed. In addition, recent developments in tuning microenvironment of SACs are systematically summarized, especially, strategies for microenvironment modulation are introduced in detail for boosting the intrinsic 4e − /2e − ORR activity and selectivity. Theoretical calculations and cutting-edge characterization techniques are united and discussed for fundamental understanding of the synthesis-construction-performance correlations. Furthermore, the techniques for building SAAS and tuning their microenvironment are comprehensively overviewed to acquire outstanding SACs. Lastly, by proposing perspectives for the remaining challenges of SACs and infant microenvironment engineering, the future directions of ORR SACs and other analogous procedures are pointed out.

Deciphering the Precursor–Performance Relationship of Single‐Atom Iron Oxygen Electroreduction Catalysts via Isomer Engineering

“…[11][12][13][14] Atomically dispersed (or single atom) metal-nitrogen-carbon (M-N-C) electrocatalysts exhibit high atom utilization, high reaction activity and high selectivity due to their unique atomic scale effect. [15][16][17][18] Therefore, M-N-C has become the research frontier of various catalytic reactions including selective oxidation, CO 2 reduction and ORR. [19][20][21][22] Generally, compared with other metal-derived M-N-C electrocatalysts, Fe-N-C materials show higher activity for ORR, and hold most potential to be a substitute for Pt-based catalyst.…”

Simultaneously Integrate Iron Single Atom and Nanocluster Triggered Tandem Effect for Boosting Oxygen Electroreduction

“…[11][12][13] Among various NPMCs, atomically nitrogencoordinated iron atoms on carbon matrix (FeNC) materials are considered to be one of the best substitutions for PMCs, which display attractive ORR activity. [14,15] With the development of advanced characterization techniques, it is increasingly recognized that atomically dispersed iron coordinated with four nitrogen atoms (FeN 4 ) in FeNC catalysts dominates the ORR activity. [16,17] According to Sabatier principle, an ideal active center for ORR needs a moderate Atomically nitrogen-coordinated iron atoms on carbon (FeNC) catalysts are emerging as attractive materials to substitute precious-metal-based catalysts for the oxygen reduction reaction (ORR).…”

Altering Local Chemistry of Single‐Atom Coordination Boosts Bidirectional Polysulfide Conversion of Li–S Batteries

“…Modulating local compositions (e.g., substituting N with P, O, and/or S atom) of metal coordinations within MNC architecture can tailor the electron distribution and thereby tune the electrochemical properties of active metal centers. [27][28][29][30] It would be meaningful to witness how altered coordination structure exerts impact on the sulfur redox kinetics. Equally importantly, developing SACs with the functions to boost bidirectional LiPS conversion is imperative yet remains elusive by far.…”