Unravelling the adsorption and electroreduction performance of CO 2 and N 2 over defective and B, P, Si-doped C 3 Ns: a DFT study.

Two-dimensional carbon-based materials have great potential for electrocatalysis. Herein, we screen 12 defective and doped C 3 N nanosheets by evaluating their CO 2 RR and NRR activity and selectivity vs. the HER based on density functional theory calculations. The calculation results suggest that all 12 C 3 Ns can enhance CO 2 adsorption and activation. And P N -V C -C 3 N is the best electrocatalyst for the CO 2 RR towards HCOOH with U L = -0.17 V, which is much more positive than most of the reported values. B N -C 3 N and P N -C 3 N are also good electrocatalysts that promote the CO 2 RR towards HCOOH ( U L = -0.38 V and -0.46 V). Moreover, we find that Si C -C 3 N can reduce CO 2 to CH 3 OH, adding an alternative option to the limited catalysts available for the CO 2 RR to CH 3 OH. Furthermore, B C -V C -C 3 N, B C -V N -C 3 N, and Si C -V N -C 3 N are promising electrocatalysts for the HER with |Δ G H* | ≤ 0.30 eV. However, only three C 3 Ns of B C -V C -C 3 N, Si C -V N -C 3 N, and Si C -V C -C 3 N can slightly improve N 2 adsorption. And none of the 12 C 3 Ns are found to be suitable for the electrocatalytic NRR because all the Δ e NNH* values are larger than the corresponding Δ G H* values. The high performance of C 3 Ns in the CO 2 RR stems from the altered structure and electronic properties, which result from the introduction of vacancies and doping elements into C 3 N. This work identifies suitable defective and doped C 3 Ns for excellent performance in the electrocatalytic CO 2 RR, which will inspire relevant experimental studies to further explore C 3 Ns for electrocatalysis.