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

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 heteroatomdoping of S atoms induced changing of center position of the pz orbital of B facilitates the adsorption of N2 on S-CB 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 mu mol 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.

Automated summary

In this study, a breakthrough was proposed in overcoming high energy barriers for N2 absorption and activation by tuning the center positions of boron in carbon nanofibers. The heteroatom doping of sulfur atoms was found to play a key role in facilitating N2 adsorption and reducing energy barriers for rate-determining steps. The novel S6.23-B8.09/CNFs showed the highest NRR activity with a Faradaic efficiency of 22.4% and NH3yield of 0.223 mu mol h-1 cm-2 at -0.7 V versus reversible hydrogen electrode, highlighting the importance of center positions in heteroatom-doped carbon catalysts for NRR activity.