Systematic theoretical research on the catalytic behaviors of p-block metal (PM)-based PM–N4 moieties is desirable to guide the design and synthesis of PM–N–C single-atom catalysts (SACs) for the oxygen reduction reaction (ORR). Herein, using first-principles calculations, the suitability of PM–N4 moieties as active sites for the ORR are systematically investigated. The results show that Sn–N4 and Pb–N4 have promising ORR activity with low overpotentials of 0.45 V and 0.55 V, respectively. For the six PM–N4 sites with strong OH* adsorption, the self-modifying effect of the intermediate OH* is further studied. In–N4–OH* upon OH* self-modification shows considerably improved ORR activity with a much lower overpotential (0.67 V) compared with that of pristine In–N4 (1.24 V). The linear OH* self-regulating mechanism is revealed for the first time, from a unique energy perspective and further verified by typical PM–N3C sites. In–N3C–OH* and Ge–N3C–OH* are located near the top of the volcano plot, with overpotentials of 0.35 V and 0.46 V, respectively. Microkinetic simulation is further used to explicitly demonstrate their ORR activities. Our work sheds light on the rational design of highly efficient main-group metal-based PM–N–C SACs for the ORR.
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