Recent advances in regulating the performance of acid oxygen reduction reaction on carbon-supported non-precious metal single atom catalysts

Developing high performance and low-cost catalysts for oxygen reduction reaction (ORR) in challenging acid condition is vital for proton-exchange-membrane fuel cells (PEMFCs). Carbon-supported non-precious metal single atom catalysts (SACs) have been identified as potential catalysts in the field. Great advance has been obtained in constructing diverse active sites of SACs for improving the performance and understanding the fundamental principles of regulating acid ORR performance. However, the ORR performance of SACs is still unsatisfactory. Importantly, microenvironment adjustment of SACs offers chance to promote the performance of acid ORR. In this review, acid ORR mechanism, attenuation mechanism and performance improvement strategies of SACs are presented. The strategies for promoting ORR activity of SACs include the adjustment of center metal and its microenvironment. The relationship of ORR performance and structure is discussed with the help of advanced experimental investigations and theoretical calculations, which will offer helpful direction for designing advanced SACs for ORR.