Improving NiNX and pyridinic N active sites with space-confined pyrolysis for effective CO2 electroreduction

Even though various nickel–nitrogen–carbon (Ni-N-C) combinations are prospective low-cost catalysts for the CO2 electroreduction reaction (CO2RR), which is one avenue for attaining carbon neutrality, the detailed role of different N species has hardly been investigated. Here, we report a hollow porous N-doped carbon nanofiber with NiNX-pyridinic N active species (denoted as h-Ni-N-C) developed using a facile electrospinning and SiO2 space-confined pyrolysis strategy. The NiNX-pyridinic N species are facilely generated during the pyrolysis process, giving rise to enhanced activity and selectivity for the CO2RR. The optimized h-Ni-N-C exhibits a high CO Faradaic efficiency of 91.3% and a large current density of −15.1 ​mA ​cm−2 ​at −0.75 ​V versus reversible hydrogen electrode in an H-cell. Density functional theory (DFT) results show that NiN4-pyridinic N species demonstrate a lower free energy for the catalyst's rate-determining step than isolated NiN4 and pyridinic N species, without affecting the desorption of CO∗ intermediate.