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Thursday, 30 September 2021

A bimetallic single atom catalyst enhances the efficiency and selectivity of CO2 reduction reaction

The use of a double-metal catalyst, presenting nearby nickel and iron active sites, improves both efficiency and selectivity of the carbon dioxide (CO2) reduction reaction, a process increasingly used to diminish the concentration of this greenhouse gas in the atmosphere. This study, published in and highlighted on the cover of Energy & Environmental Science, has been led by ICN2 group leader Prof. Jordi Arbiol.

Carbon dioxide (CO2) emission from fossil fuel combustion represents a major threat to environmental preservation and global climate. Among various approaches attempted to reduce the concentration of CO2 in the Earth’s atmosphere is its electrochemical reduction, whereby CO2 is converted into other chemical species (such as carbon monoxide, formic acid, methane, ethylene and ethanol), which can be used as feedstock or chemicals for various applications. This process, though, is not very efficient, because of the inertness of CO2 molecules and the presence of a competitive reaction (hydrogen evolution reaction) taking place during the electrocatalysis.

Single-atom catalysts (SACs), thanks to the higher density of exposed catalytic sites, can provide high selectivity and suppression of the competing reaction. Nickel (Ni)-based SACs have been explored for this application, leading to an improved electrochemical CO2 reduction reaction. These catalysts, though, exhibit overpotentials, which means that the energy consumed to drive the reaction is higher than what electrodynamically needed.

In a research recently published in Energy & Environmental Science and featured on its cover, the use of a bimetallic single atom catalyst is proposed, which combines the advantages of nickel- and iron-based catalysts, where the first optimize the initial step of the reaction –i.e. the desorption of CO— and the second provide low overpotential for the CO2 reduction. This study has been coordinated by ICREA Prof. Jordi Arbiol, leader of the ICN2 Advanced Electron Nanoscopy Group, and by Prof. Joan Ramon Morante of the Catalonia Institute for Energy Research of Barcelona (IREC), and carried out by an international team including researchers from  Shangai Tech University and the Institute of Microsystem and Information Technology of Shangai (China), the Southwest University of Changqing (China) and the Katholieke Universiteit Leuven (Belgium). First authors of the paper are Dr Ting Zhang and Xu Han, respectively postdoctoral researcher and PhD student in Prof. Arbiol’s group.

The compound adopted by the authors of this work (Ni7/Fe3-N-C) exhibited excellent catalytic activity, since closely positioned Ni and Fe active sites affect positively different steps of the CO2 reduction reaction. This configuration, on the one hand, provides excellent selectivity to CO2 evolution, boosting absorption and desorption of intermediates in the reduction process, and, on the other, guarantees a low overpotential, which leads to less energy consumption. In addition, undesired competing reactions are strongly limited.

The results of this research proves that catalysts with nearby double-metal single atoms can improve the efficiency and selectivity of CO2 reduction reactions, as compared to single metal counterparts. Furthermore, the combination of Ni and Fe active sites demonstrates to act as a nano-reactor, since multistep reactions take place simultaneously with an improved overall activity and selectivity. The same strategy could be applied to enhance other electrocatalytic processes, which suffer from similar limitations.

 

Reference article:

Ting Zhang, Xu Han, Hong Liu, Martí Biset-Peiró, Xuan Zhang, Pingping Tan, Pengyi Tang, Bo Yang, Lirong Zheng, Joan Ramon Morante and Jordi Arbiol, Quasi-double-star nickel and iron active sites for high-efficiency carbon dioxide electroreduction. Energy & Environmental Science, Issue 9, 2021, 14, 4847-4857. DOI: 10.1039/D1EE01592C