Benchmarking the Oxygen Reduction Electroactivity of First‐Row Transition‐Metal Oxide Clusters on Carbon Nanotubes

Abstract

Transition-metal oxide/nanocarbon hybrids are known to deliver a cooperative oxygen reduction reaction (ORR) with a synergistic effect of the hybrid interface. This work assesses a series of first-row transition-metal oxides in the form of surfaceconfined clusters on carbon nanotubes, as a mimic of fully exposed hybrid interfaces, providing an activity benchmark for hybrid catalysts. Among the selected metal oxides, MnO x and CoO x are found to be the most active first-row transition-metal oxide clusters for the ORR, given their excellent peroxidereducing capability at low overpotential. FeO x and CuO x are also active for the same role, except their peroxide-reducing activity is only activated with substantial overpotential. Other metal oxides (NiO x and ZnO x ) do not appear to show any activity toward the ORR, even with an integrated interface as a source for the possible synergistic effect.

Oxygen Electrocatalysis at MnIII–Ox–C Hybrid Heterojunction: An Electronic Synergy or Cooperative Catalysis?

“…The bottom-up fabrication started from a facile surface reaction on the OCNT in solution via specific metal−oxygen binding (as illustrated in Figure 1b). 18 The supporting OCNT was only mildly oxidized for enriching the surface oxygen content (16.0 atom %) (Figure S3a, Supporting Information), while preserving the electrical conductivity. 19 During the binding process, the surface oxygen groups, especially the epoxyl and hydroxyl groups (Figure S3b), acted as anchors to Mn 2+ ions in a pH 5.0−6.0 solution (growth and precipitation is prohibited at this pH).…”

Advanced Characterization Techniques for Identifying the Key Active Sites of Gas‐Involved Electrocatalysts

“…[ 41 ] It has been widely acknowledged that Mn 4 C 4 is considered as the OER activity moieties, [ 30b ] while MnO x and CoO x are the most active first‐row TM oxides clusters for catalyzing ORR. [ 42 ] Further clarification of these “structure units” may open a new avenue for the convenient and precise synthesis of highly efficient catalysts. Therefore, trying to analyze the active structure of the catalysts combined with those advanced characterization techniques and theoretical calculation is interesting and necessary to guide future direction of this area.…”

Highly electroactive N–Fe hydrothermal carbons and carbon nanotubes for the oxygen reduction reaction

“…The oxygen reduction reaction (ORR) takes place in several electrochemical systems such as fuel cells and metal-air batteries [1][2][3][4][5][6][7] . The main problem of this reaction is its slow kinetics, that hinders the overall performance of these electrochemical devices [2-5 , 7-10] .…”