Unravelling the adsorption and electroreduction performance of CO2 and N2 over defective and B, P, Si-doped C3Ns: a DFT study

Abstract

Two-dimensional carbon-based materials have great potential for electrocatalysis. Herein, we screen 12 defective and doped C₃N nanosheets by evaluating their CO₂RR and NRR activity and selectivity vs. the HER based on density functional theory calculations. The calculation results suggest that all 12 C₃Ns can enhance CO₂ adsorption and activation. And P_N–V_C–C₃N is the best electrocatalyst for the CO₂RR towards HCOOH with U_L = −0.17 V, which is much more positive than most of the reported values. B_N–C₃N and P_N–C₃N are also good electrocatalysts that promote the CO₂RR towards HCOOH (U_L = −0.38 V and −0.46 V). Moreover, we find that Si_C–C₃N can reduce CO₂ to CH₃OH, adding an alternative option to the limited catalysts available for the CO₂RR to CH₃OH. Furthermore, B_C–V_C–C₃N, B_C–V_N–C₃N, and Si_C–V_N–C₃N are promising electrocatalysts for the HER with |ΔG_H*| ≤ 0.30 eV. However, only three C₃Ns of B_C–V_C–C₃N, Si_C–V_N–C₃N, and Si_C–V_C–C₃N can slightly improve N₂ adsorption. And none of the 12 C₃Ns are found to be suitable for the electrocatalytic NRR because all the Δe_NNH* values are larger than the corresponding ΔG_H* values. The high performance of C₃Ns in the CO₂RR stems from the altered structure and electronic properties, which result from the introduction of vacancies and doping elements into C₃N. This work identifies suitable defective and doped C₃Ns for excellent performance in the electrocatalytic CO₂RR, which will inspire relevant experimental studies to further explore C₃Ns for electrocatalysis.