Nitrogen fixation on metal-free SiC(111) polar surfaces
Boron atom as an electron “acceptation-donation” center induced nitrogen fixation has recently been reported in both molecular (Science 2018, 359, 896) and heterogeneous catalysis (JACS 2018, 140, 14161 & JACS 2019, 141, 2884). In this work, we reported an alternatively economic metal-free SiC as an excellent nitrogen fixation catalyst. The surface Si or C on SiC(111) behaves similarly to the boron atom with the strong bonding and activation of N2, and the effectively reduced N2 to NH3 on Si-terminated surface has a low limiting potential (-0.54 V). More important, the adsorbed N2 can be efficiently reduced to NH3 on C-terminated SiC(111) with a rather low limiting potential (-0.22 V) via an enzymatic pathway and the hydrogen evolution reaction can be significantly inhibited, indicating its excellency in the selectivity and efficiency. Overall, our study provides insights into the nitrogen fixation on SiC and more importantly extends a series of catalysts beyond boron for converting nitrogen into more valuable NH3 on abundant metal-free catalysts.