Efficient CO₂ Electroreduction by Highly Dense and Active Pyridinic Nitrogen on Holey Carbon Layers with Fluorine Engineering

Abstract

Electrocatalytic CO2 reduction by metal-free nitrogen-doped carbon (N-C) catalysts provides a solution for CO2 reuse; however, it suffers a large overpotential and poor selectivity due to the low intrinsic reactivity of N dopants. Herein, we report the promotion of CO2 reduction on N-C through the integration of increasing the numbers and inherent catalytic reactivity and selectivity of pyridinic N dopants. A novel sacrificial soft-templating approach was developed to construct a two-dimensional holey carbon nanostructure to preferentially host dense edge-located pyridinic N, and electron-rich fluorine (F) was simultaneously incorporated to activate pyridinic N sites by engineering their electronic properties. Consequently, the resultant N,F-codoped holey carbon layers achieve a CO Faradaic efficiency of 90% at a low overpotential of 490 mV for 40 h without decay, significantly surpassing the F-free N-C counterpart. Density functional theory (DFT) calculations reveal that the electron donation from a nearby F atom increases the charge density and delocalizes electronic density of states of pyridinic N. These electronic benefits thus greatly promote the CO2 activation on the highly dense and active pyridinic N sites by facilitating the electron transfer and strengthening the binding interaction with *COOH intermediate. The discovery of dopant-induced synergistic interaction may create a path for manipulating catalytic CO2 reduction properties.

Optimization Strategies for Selective CO2 Electroreduction to Fuels

“…The *HCOO pathway has a lower energy barrier than CO 2 δ− , contributing to the improvement in CO 2 hydrogenation performance. Deng et al [84] found that the *OH coverage on hydroxyl functionalized Sn branches (Sn-OH) is influential to CO 2 RR catalytic properties because excess *OH will occupy active sites and cause the reduction of Sn-OH to Sn. With careful manipulation, the best performed Sn-OH with optimal *OH concentration shows the highest FE HCOOH up to 82.5% at − 1.8 V versus Ag/AgCl.…”

Electrochemical Reduction of CO2 to CO by N,S Dual‐Doped Carbon Nanoweb Catalysts

“…Previous theoretical calculations revealed that a lower Gibbs free‐energy barrier for *COOH formation occurs in a pyridinic N adjacent to the thiophene‐like S, whereas a higher Gibbs free energy on pyridinic N species requires extra energy to overcome the barrier of *COOH formation . In addition, the incorporation of F atoms with an electron‐donating nature into N‐doped carbons could alter the electronic properties of pyridinic N, which helps to boost the CO 2 activation for CO production . Furthermore, recent work has demonstrated that the inductive effect caused by electron‐donating and electron‐withdrawing groups of pyridine‐based molecules could play an important role in CO 2 reduction to CH 3 OH .…”

“…[23] In addition, the incorporation of F atomsw ith an electron-donating nature into N-doped carbons could alter the electronic properties of pyridinic N, which helps to boost the CO 2 activation for CO production. [22] Furthermore, recent work has demonstrated that the inductivee ffect caused by electron-donatinga nd electron-withdrawing groups of pyridine-based molecules could play an important role in CO 2 reductiont oC H 3 OH. [47] On the basis of the aforementioned results and previouss tudies,w ed educed that the high catalytic activity and selectivity for CO 2 reduction to CO on NSCNW-3 were probably owing to the structural advantages and appropriate Sm odification.…”

“…For example, Pan et al. reported a significant enhancement in CO 2 RR activity for CO production by incorporating fluorine (F) atoms into N‐doped carbons, suggesting that the electron donation from F could improve the intrinsic catalytic activity and selectivity of pyridinic N for CO production . It has also been reported that additional S doping in N‐doped carbons could further reduce the Gibbs free energy of formation of *COOH as the rate‐determining step for the CO 2 ‐to‐CO conversion .…”

Plasma-regulated N-doped carbon nanotube arrays for efficient electrosynthesis of syngas with a wide CO/H2 ratio

“…Though the intrinsic activity of carbon materials is poor, the introduction of heteroatoms (N, S, B, etc.) can effectively promote their electrochemical activity and selectivity [19][20][21][22][23]. Taking N-doped carbon materials as the examples, the doping N atoms exist in the forms of pyridinic N, pyrrolic N, graphitic N, and oxidized N in the carbon materials.…”