Electro-functionalized 2D nitrogen-carbon nanosheets decorated with symbiotic cobalt single-atoms/clusters

Two-dimensional (2D) materials loaded with single atoms and clusters are being set at the forefront of catalysis due to their distinctive geometric and electronic features. However, the usually-complicated synthesis procedures impede in-depth clarification of their catalytic mechanisms. To this end, herein we developed an efficient one-step dimension-reduction carbonization strategy, with which we successfully architected a highly-efficient catalyst for oxygen reduction reaction (ORR), featured with symbiotic cobalt single atoms and clusters decorated in two-dimensional (2D) ultra-thin (3.5 nm thickness) nitrogen-carbon nanosheets. The synergistic effects of the two components afford excellent oxygen reduction activity in alkaline media (E_1/2 = 0.823 V vs. RHE) and thereof a high power density (146.61 mW cm⁻²) in an assembled Zn-air battery. As revealed by theoretical calculations, the cobalt clusters can regulate electrons surrounding those individual atoms and affect the adsorption of intermediate species. As a consequence, the derived active sites of single cobalt atoms lead to a significant improvement of the ORR performance. Thus, our work may fuel interests to delicate architecture of single atoms and clusters coexisting 2D support toward optimal electrocatalytic performance.