Developing nonprecious electrocatalysts operating in acidic and alkaline media for an oxygen reduction reaction (ORR) is essential for sustainable energy technologies. Increasing the metal active site density is an effective strategy to enhance the activity, but it remains challenging because of metal sintering during pyrolysis. Here, we report a novel strategy of enriching atomically dispersed cobalt species in nitrogen-doped carbon for improving the electrocatalytic performance. A hollow carbon nanosphere with reduced shell thickness was obtained by taking advantage of the carbothermic reaction between carbon and ZnO template, and the resulting cobalt enrichment in the ultrathin carbon shell leads to an increase of the density of Co atoms. Together with advantageous microstructure features such as high surface area and multiscale porosity, the corresponding catalyst demonstrated promising oxygen reduction reaction performance in strong acidic and alkaline electrolytes and has two times higher kinetic current density than the nonenriched one. The present work provides an attractive and facile route to engineer active site in electrocatalysts.

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Oxides supported precious metals have wide applications in (electro‐)catalysis. Although single atom dispersion is known as the most efficient metal utilization strategy, the dependence of the catalytic activity on different sites consisted of various anchoring sites for single atoms is largely unknown. Here, the electrocatalytic activities of crystalline α‐MnO2 with atomistic Pd locating at different sites including substitutional, tunnel, and surface‐bound sites are first predicted, and then experimentally validated by applying different synthetic methods including hydrothermal reaction and impregnation‐calcination. The quantum chemistry calculations together with experimental characterization suggest that substitutional Pd/MnO2 possesses higher activity than the other samples due to the favorable geometric and electronic structures. Substitutional Pd can work synergistically with vicinal Mn sites toward cleavage of OO bonds. This work provides a comprehensive understanding on the impact of atomistic anchoring site and advances the reliable control over the electrocatalytic performance of oxide‐supported single atoms.

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Fig. 1. Case I: (1) Select a product within the red circle among all 361°sneakers in the Product Overview. (2) Browse the product description of the selected product at the buttom of the scatter chart. (3) View the annual data of the selected product in the Promotion Overview. (4) Adjust the time period selector in the Sales Prediction View. (5) Look through the dotted lines and find non-overlapping zones. (6) Change the promotion strategy in the Strategy View -exchange the value discount that exists with the same discount rate and percentage discount for the time period. (7) Discover that sales have decreased. (8) Conclude that the value discounts may be appropriate for the selected product. (9) Compare similar products in the glyphs, word clouds and box plots in the Competitive Analysis View, and select another XTEP product. (10) Adjust the time selector to fix a time period for the newly selected product. (11) Replace the existing percentage discount in the Strategy View with the same discount rate and value discount for the time period. (12) Find that sales have decreased. ( 13) Conclude that the percentage discount may be appropriate for the selected product.