Optimizing the Electrocatalytic Selectivity of Carbon Dioxide Reduction Reaction by Regulating the Electronic Structure of Single‐Atom M‐N‐C Materials

Abstract

Electrochemical carbon dioxide reduction reaction (CO2RR) is an efficient strategy to relieve global environmental and energy issues by converting excess CO2 from the atmosphere to value‐added products. Atomically dispersed metal‐nitrogen‐doped carbon (M‐N‐C) materials are superior catalysts for electrocatalytic CO2RR because of the 100% atomic utilization, unsaturated coordination configuration, relatively uniform active sites, and well‐defined and adjustable structure of active centers. However, the electrochemical CO2RR is a great challenge due to the process involving proton‐coupled multi‐electron transfer with a high energy barrier, which leads to unsatisfactory selectivity to the targeted product, especially for C2 products (e.g., C2H4 and C2H5OH). Here, the authors systematically summarize effective means, including reasonable selection of isolated metal sites, regulation of the coordination environment of isolated metal atoms, and fabrication of dimetallic single‐atom sites for attaining optimal geometric and electronic structures of M‐N‐C materials and further correlate these structures with catalytic selectivity to various C1 (e.g., CO and CH4) and C2 products in the CO2RR. Moreover, constructive strategies to further optimize M‐N‐C materials for electrocatalytic CO2RR are provided. Finally, the challenges and future research directions of the application of M‐N‐C materials for electrocatalytic CO2RR are proposed.

Tailoring of Active Sites from Single to Dual Atom Sites for Highly Efficient Electrocatalysis

“…Nevertheless, a high catalyst loading is necessary to realize a high overall electrocatalytic performance, which can potentially lead to a mass-transport issue. Although there are recent reports about the increased metal loading above 5 wt % in SACs by adopting sophisticated methods in lab scale, − the low metal loading and unsatisfactory metal site density are still the main challenges, and this is a long way from industrial applications, especially for traditional approaches such as wet chemistry based, simple high temperature pyrolysis, and atomic layer deposition. ,− On the other hand, a strong bond between isolated single atoms and supports can also contribute to the stability of SACs, but this strong interaction may also affect the electronic states of single atoms. Such an interaction can induce an electron-donation from metal atoms to supports, which yields more oxidic single atoms and manifestly alters the intrinsic activity.…”

Self-Supporting Metal-Organic Framework-Based Nanoarrays for Electrocatalysis

“…To meet the rapidly growing global energy demand and ease the heavy reliance on nonrenewable fossil fuels, enormous efforts have been made to develop and improve clean renewable energy storage and conversion technologies. , Specifically, electrochemical energy conversion between electricity and chemicals by electrocatalysis is a promising key technology, which can realize the efficient utilization of intermittent renewable energy and provide basic raw materials and fuels for the chemical industry. , However, electrocatalysis still has many bottlenecks that seriously hinder its practical applications. For example, oxygen evolution reaction (OER) involving multiple electron-proton transfers has slower reaction kinetics, which limits the overall efficiency of electrolytic water. , Hydrogen evolution reaction (HER) requires overcoming extra energetic barriers to generate reaction intermediates in alkaline media, and its reaction kinetics is about 3 orders of magnitude lower than those in acidic media. , Oxygen reduction reaction (ORR) is an important cathodic reaction in fuel cells, but its slow kinetic process significantly limits the large-scale application. , Besides, electrochemical carbon dioxide reduction reaction (CO 2 RR) shows low Faraday efficiency (FE) and poor product selectivity due to competitive HER and complex proton-coupled multistep reaction process. , The slow kinetics of methanol oxidation reaction (MOR) also limits the commercialization of direct methanol fuel cells. , Therefore, rational exploration and design of electrocatalysts with excellent activity, selectivity, and long-term durability are the keys to the development of electrocatalytic energy conversion technology.…”

High-Throughput Computational Screening of Metal–Organic Frameworks as High-Performance Electrocatalysts for CO2RR

“…In the context of peak carbon dioxide emissions and carbon neutrality, highly efficient CO 2 capture and conversion technologies have become increasingly important. − However, due to the high bond energy of the C–O bond, CO 2 molecules are chemically inert and difficult to be activated. , One of the main challenges of the carbon dioxide reduction reaction (CO 2 RR) is to develop catalysts that can break C–O bonds and selectively generate specific products. − Among many CO 2 conversion strategies, electrocatalysis has been widely studied because of its ability to convert CO 2 into high-value-added chemicals and fuels. − …”