Oxygen‐Coordinated Cr Single‐Atom Catalyst for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

Carbon‐supported metal single‐atom catalysts (M‐SACs) are promising oxygen reduction reaction (ORR) catalysts. Their ORR activity and selectivity are significantly affected by the heteroatoms that coordinate the central metal atoms. Previous reports found that oxygen‐coordinated M‐SACs promoted a 2e‐ ORR rather than the 4e‐ ORR that is more desirable for fuel cells. Herein, we report for the first time that oxygen‐coordinated M‐SACs are capable of promoting the 4e‐ ORR in acid media. We prepared a Cr(acac)‐NC catalyst with the central Cr atom coordinated by two O atoms. The Cr(acac)‐NC catalyst not only exhibits excellent ORR activity and stability in acid media, but also delivers high proton exchange membrane fuel cell (PEMFC) performance comparable to N‐coordinated M‐SACs. Density functional theory (DFT) calculations reveal that Cr‐O2 moieties located on the zigzag edge of the carbon support are the ORR‐active sites.