Porous aza-doped graphene-analogous 2D material a unique catalyst for CO2 conversion to formic-acid by hydrogenation and electroreduction approaches

Abstract

In this work, we report novel single-layered porous aza-fused π-conjugated graphene-analogous 2D materials (PAG) with well-organized nanopores and consistently allocated nitrogen atoms as supporting specie to coordinate cobalt (Co) atom through nitrogen inside (Co-PAG), for CO2 conversion to formic-acid by hydrogenation and electrochemical approaches. Because of the synergetic effect of structural characteristics and Co-coordination, the band gap of Co-PAG is reduced to 0.7 eV, while that of PAG is 1.79 eV. The molecular dynamic (MD) simulations uncover the stability of PAG/Co-PAG. From reaction pathway analysis, it is concluded that Co-PAG can effectively hydrogenate CO2 to formic acid. The highest barrier is 0.78 eV, which is feasible for experiments to carry out this reaction at elevated temperatures. Furthermore, the overpotential requirement for PAG material in CO2 electroreduction (CO2RR) to formic-acid is 0.46 V which is significantly larger than that for Co-PAG (0.18 V). Both PAG and Co-PAG surfaces retain higher selectivity for formic acid than that of carbon mono oxides and hydrogen evolution reaction (HER), and cobalt coordination in PAG support makes the formic-acid reaction path significantly energy favorable. These results confirm that PAG can be possible catalyst support and that Co-coordination in PAG material makes the formic-acid reaction path significantly more energy favorable.