Optimizing FeNC Materials as Electrocatalysts for the CO₂ Reduction Reaction: Heat‐Treatment Temperature, Structure and Performance Correlations

Abstract

The direct CO 2 electrochemical reduction reaction (CO2RR) into carbon-based chemicals has attracted tremendous attention as a sustainable process for CO 2 utilization. The viability of the process, however, is contingent on finding efficient catalysts based on earth abundant elements. Carbon-based solid catalyst materials doped with nitrogen and transition metals (MÀ NÀ C) have emerged as a cost-efficient alternative for the direct electrochemical reduction of CO 2 into CO. These materials contain different N functionalities and MN x moieties which could be involved in the catalytic process. With the aim of gaining insight into the role of these different active sites and how to control their concentration we have prepared 5 polyani-line derived FeNC catalysts by changing the temperature of the heat treatment (750-1050°C). We observed that it is possible to tune the ratio of the different N functionalities by changing the pyrolysis temperature. Furthermore, this had a clear impact on the catalytic performance of this family of FeNC materials. In particular, a higher temperature correlated with a larger FeN x concentration resulting in a high selectivity toward the CO2RR. These results indicate that FeN x moieties play a predominant role in the catalytic process and that the incorporation of such sites to the carbon structure is enhanced by the heat-treatment temperature.

CO2 electrochemical reduction on metal–organic framework catalysts: current status and future directions

“…This process results in inhomogeneous materials containing a variety of chemical functionalities, including metal centers coordinated to nitrogen in MN x moieties, similar to those on metal macrocycles. 25…”

Recent progress in electrochemical reduction of carbon dioxide on metal single‐atom catalysts

“…To further study the correlations between the reaction activity and material structure, González‐Cervantes et al 68 prepared Fe‐SACs on nitrogen‐doped carbon by the pyrolysis method. By monitoring the reaction performance on the catalysts treated under different pyrolysis temperature, they observed a clear impact on the catalytic performance.…”

“…These results indicated that FeN x moieties played a predominant role in the reaction. However, an overall current density decreased, which resulted from the smaller surface area and micropore area caused by the high temperature treatment 68 …”

“…(A) Selectivity after 15 min of CO 2 , and (B and C) the selectivity of CO and CH 4 as a function of potential 68 . Copyright © 2021, John Wiley and Sons…”

“…Typically, the temperature was heated up to near 1000°C; after heat treatment, acid leaching was used to remove large particles. However, high temperature treatment might result in support agglomeration and surface area decrease, which lowers the catalytic performance 68 . In addition, it is hard to control the coordination environment of metal atoms to reveal the real active sites and investigate the effect of electronic structure.…”