Metal-free boron and sulphur co-doped carbon nanofibers with optimized p-band centers for highly efficient nitrogen electroreduction to ammonia

Abstract Herein, we proposed a conceptual and experimental breakthrough in overcoming the high energy barriers for N2 absorption and activation by tuning the center positions of pz orbital of boron in S and B co-doped carbon nanofibers (S-B/CNFs). We theoretically and experimentally investigated the influences of nonmetallic elements of B as electron acceptor, and S and P as electron donor on tuning NRR activity. We revealed that the heteroatom-doping of S atoms induced changing of center position of the pz orbital of B facilitates the adsorption of N2 on S-C-B sites and reduces the energy barriers for rate-determining steps. The S6.23-B8.09/CNFs exhibits the highest NRR activity with high Faradaic efficiency of 22.4 % and NH3 yield of 0.223 μmol h-1 cm-2 at −0.7 V versus reversible hydrogen electrode. The combined computational and experimental works uncover the relationship between the p-band center of heteroatom doped carbon catalysts and NRR activity.