Spatial Sites Separation Strategy to Fabricate Atomically Isolated Nickel Catalysts for Efficient CO2 Electroreduction

Fabrication of highly active carbon-supported atomically isolated metal catalysts with maximized atomic efficiency is significant but remains a big challenge because the adjacent metal species are easy to be aggregated during pyrolysis. Herein, a spatial sites separation strategy is developed to fabricate fully atomically isolated nickel catalysts for highly efficient CO 2 electroreduction reaction (CO 2 RR). The porous porphyrinic triazine frameworks (designated as PTF-Zn, PTF-ZnNi x, and PTF-Ni 100, x = 5, 20, refers to molar percentage of Ni-TPPCN monomer) were first obtained by the polymerization of the monomers 5,10,15,20-tetrakis(4-cyanophenyl)porphyrin (TPPCN) or [5,10,15,20-tetrakis(4-cyanophenyl)porphyrinato]-Ni (Ni-TPPCN) with different molar ratios in the presence of ZnCl 2 . The distances between the Ni-N 4 units that spatially separated by in situ formed Zn-N 4 units in these PTF frameworks can be controlled by tuning the ratio of the monomers of Ni-TPPCN and TPPCN. Thus, because of the successful implementation of spatial sites separation strategy, pyrolysis of PTF-ZnNi 5 that the Ni-N 4 units were separated by Zn-N 4 moieties afforded Ni 5 -PFT-1000 with fully atomically isolated Ni active sites. In contrast, pyrolysis of PTF-ZnNi 20 or PTF-Ni 100 led to porous carbon catalysts containing nickel nanoparticles (Ni NPs) because of the very limited spatial separation of Ni-N 4 units with or without Zn-N 4, allowing Ni migration and aggregation to occur. Consequently, porous Ni 5 -PTF-1000 was highly active for CO 2 RR toward CO with a high Faradaic efficiency (FE) of 94% at −0.9 V, larger CO partial current density of 18.4 mA cm –2, high turnover frequency value (TOF) of 20180 h –1 at −1.0 V. In contrast, Ni 20 -PFT-1000 and Ni 100 -PFT-1000 containing Ni NPs had lower FE of 79.7% and 6.8%, respectively, for the conversion of CO 2 -to-CO at the same potential. This work presents a facile way to achieve highly active catalyst with fully atomically dispersed sites for CO 2 RR catalysis.