Atomically dispersed Fe-N-P-C complex electrocatalysts for superior oxygen reduction

The P-O-Fe bond and the redox cycle between N-P-O-Fe-O and N-P-O-Fe-O2 on atomically dispersed Fe-N-P-C complex catalyst prepared directly form woody biomass efficiently reduced adsorption strength of OH*, which leads to outstanding ORR activity. [Display omitted] •Atomically dispersed Fe-N-P-C catalysts produced from woody biomass.•Outstanding ORR performance achieved.•Fe charge in the active site identified as descriptor.•P-O-Fe bond and the redox cycle of active sites resulted in the high activity. Development of cost-effective electrocatalysts as an alternative to platinum for oxygen reduction reaction (ORR) is of great significance for boosting the applications of green energy devices such as fuel cells and metal-air batteries. Here we report a nitrogen and phosphorus tri-doped hierarchically porous carbon supported highly cost-effective, efficient and durable Fe single-site electrocatalyst derived from biomass. Combined aberration-corrected HAADF-STEM, XPS and XAFS measurements and theoretical calculations reveal the atomically dispersed Fe-N-P-C-O complex as the dominant active sites for ORR. This work also shows the design principle for enhancing the ORR activity of single Fe site catalysts with higher Fe charge, which can be manipulated by the coordinated structure in the active centre. Theoretical calculations reveal that the main effective sites are singleN-P-O-Fe-O centers, where the associated P-O-Fe bond can significantly lower the stability of strongly adsorbed O* and OH* on the catalytically active sites and thus give rise to enhanced ORR performance. The insights reported here open a new avenue for constructing highly efficient molecule-like heterogeneous catalysts in electrochemical energy technologies.