Electrochemical reduction of CO₂ (CO₂RR) using renewable electricity has emerged as an attractive approach to synthesize hydrocarbons and mitigate atmospheric CO₂ concentration. Carbon-based materials have recently attracted a particular attention as electrocatalysts for CO₂RR due to their extraordinary properties such as low cost and flexibility in tuning the morphology and electronic structure. Wide range of different N-doped carbon materials have been experimentally tested and reported for CO₂RR. The performance map for CO₂RR over reported N-doped carbon-based materials presents diverse activities and in most cases the major product of the CO₂ reduction is found to be CO. Based on a simple thermochemical analysis Wu et al previously suggested pyridinic-N as the active sites.¹ Using density functional theory (DFT) calculations we study a wide range of different possible active motifs included in the defective carbon materials to rationalize the associated trends in their intrinsic activities. We study both CO₂RR and hydrogen evolution reaction (HER) using thermochemical analysis. We identify several active motifs that are expected to exhibit a comparable or even better activity to the state-of-the-art gold catalyst, and several configurations are suggested to be selective for CO₂RR over HER. This study provides insights in the nature of active and selective motifs for CO₂RR and rationalizes a number of reports in the literature.² We also show that in the presence of metal impurities further reduced products can be synthesized with significantly improved activity and selectivity.

References:

(1) Wu, J.; Yadav, R. M.; Liu, M.; Sharma, P. P.; Tiwary, C. S.; Ma, L.; Zou, X.; Zhou, X.-D.; Yakobson, B. I.; Lou, J.; Ajayan, P. M. ACS Nano 2015, 9 (5), 5364–5371.

(2) Siahrostami, S.; Jiang, K.; Karamad, M.; Chan, K.; Wang, H.; Nørskov, J. ACS Sustain. Chem. Eng. 2017, acssuschemeng.7b03031.

(3) Jiang, K.; Siahrostami, S.; Li, Y.; Lu, Z.; Gardener, J.; Lattimer, J; Stokes, C.; Hill, W.; Bell, D.; Chan, K.; Nørskov, J.K.; Yi Cui, Y.; Wang, H. Chem 2017 https://doi.org/10.1016/j.chempr.2017.09.014.