Oxygen reduction reaction (ORR) presents multi-products characteristic due to the different reaction paths, such as O2 could be reduced to H2O via 4e- pathway, or to H2O2 via 2e- pathway. Easily overlooked, hydroxyl radicals could be produced by (2+1) e- pathway in ORR. Hydroxyl radicals, as the strong oxidant, play an important role in chemical synthesis, medical treatment and environmental remediation, but the selective production of hydroxyl radical is difficult to regulate. In this study, a dual-active-site strategy was reported to selectively electrochemically reduce O2 to hydroxyl radicals. Combining the concepts of single-atom catalysis and dual-active-site, we designed a Co/Fe bimetallic atomically dispersed catalyst on N doped carbon (CoFe DAC), in which O2 tends to be selectively reduced to H2O2 at Co sites and H2O2 intermediate is subsequently reduced to hydroxyl radicals at Fe sites. DFT calculation revealed that the synergistic effect between isolated Co and Fe sites in CoFe DAC could regulate the binding energy of *OOH and *H2O2 intermediates in O&lt;span style="font-size:10.8333px"&gt;RR &lt;/span&gt;process, thereby promoting the production of hydroxyl radicals. The production rate of hydroxyl radicals of CoFe-NOC catalyst reached 2.42 mmol L-1min-1gcatalyst-1, which was the best level among the reported eletrocatalysts. This work presents a great possibility for rational design of single-atom catalysts for multi-intermediate electrochemical reactions.

Selective electrocatalytic reduction of oxygen to hydroxyl radicals boosted by synergistic effect between atomically dispersed Fe and Co sites

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ACS Fall 2022

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