Opportunity of Atomically Thin Two-Dimensional Catalysts for Promoting CO₂ Electroreduction

ConspectusExcessive use of fossil fuels has not only led to energy shortage but also caused serious environmental pollution problems due to the massive emissions of industrial waste gas. As the main component of industrial waste gas, CO2 molecules can also be utilized as an important raw material for renewable fuels. Thus, the effective capture and conversion of CO2 has been considered one of the best potential strategies to mitigate the energy crisis and lower the greenhouse effect simultaneously.In this case, CO2 electroreduction to high-value-added chemicals provides an available approach to accomplish this important goal. Nonetheless, the CO2 molecule is extremely stable with a high dissociation energy. With regard to the traditional electrocatalytic systems, there are three main factors that hinder their practical applications: (i) sluggish carrier transport dynamics; (ii) high energy barrier for CO2 activation; (iii) poor product selectivity. Therefore, solving these three crucial problems is the key to the development of efficient electrocatalytic CO2 reduction systems.Considering that the CO2 molecule is a typical Lewis acid with a high first ionization energy and electronic affinity, electron-rich catalysts could help to activate the CO2 molecule and improve the conversion efficiency. In view of this, atomically thin two-dimensional electrocatalysts, benefiting from their significantly increased density of states near the Fermi level, have great potential to effectively accelerate the dynamics of electron transport. Moreover, their high fraction of surface active sites and enhanced local charge density could remarkably reduce the energy barrier for CO2 activation. Furthermore, their modulated electronic structure could alter the catalytic reaction pathway and improve the product selectivity. Meanwhile, the concise two-dimensional configuration facilitates in situ characterization as well as the establishment and simulation of theoretical models, which helps to reveal the mechanism of electrocatalytic CO2 reduction, thereby speeding up the development of CO2 conversion technology.In this Account, we summarize recent progress in tailoring the electronic structure of atomically thin two-dimensional electrocatalysts by different methods. Meanwhile, we highlight the structure-property relationship between the electronic structure regulation and the catalytic activity/product selectivity of atomically thin two-dimensional electrocatalysts, and discuss the underlying fundamental mechanism with the aid of in situ characterization techniques. Finally, we discuss the major challenges and opportunities for the future development of CO2 electroreduction. It is expected that this Account will help researchers to better understand CO2 electroreduction and guide better design of high-performance electrocatalytic systems.