Advances in porousizing catalysts for boosting CO2 electroreduction

With the continuous growth of global energy demand and escalating environmental issues, CO₂ emissions have surged dramatically, reaching up to 54 billion tons annually, capturing worldwide attention. Converting CO₂ into high-value chemicals not only helps mitigate global climate change but also promotes the development of the carbon cycle and green chemistry. Electrochemical CO₂ reduction reactions (eCO₂RR) offer an effective pathway for this conversion, and porous materials, with their unique physicochemical properties, have demonstrated tremendous potential in these reactions.

Published in the Chinese Journal of Catalysis (https://doi.org/10.1016/S1872-2067(24)60147-6), the review by Zhiyong Tang and collaborators at the National Center for Nanoscience and Technology delves into the role of porous catalysts in enhancing CO₂ electroreduction.

The research team first introduced the synthesis techniques of porous materials, including template methods and template-free methods, which can precisely control the size, shape, and distribution of porous structures. They then summarized the design strategies for combining porous materials with eCO₂RR, such as loading catalytic metal single atoms, molecules, and nanoparticles onto porous supports to enhance the exposure of active sites and optimize local reaction conditions. Additionally, the team explored the reaction mechanisms of eCO₂RR, analyzing key reaction intermediates for different target products.

The research team first introduced various synthesis techniques for porous materials, including both template-based and template-free methods. These methods allow for precise control over the size, shape, and distribution of porous structures. They then summarized design strategies for integrating porous materials with eCO₂RR, such as loading catalytic metal single atoms, molecules, and nanoparticles onto porous supports to increase the exposure of active sites and optimize local reaction conditions. Additionally, the team explored the reaction mechanisms of eCO₂RR, analyzing key reaction intermediates for different target products.

Enrichment Effect: Porous structures can enrich key intermediates, such as *CO, thereby increasing the selectivity of C₂₊ products. For instance, by adjusting the pore size of porous Cu catalysts, researchers found that a Cu catalyst with a pore size of 20 nm achieved an ethylene Faraday efficiency of 85.6% and a constant current density of 368 mA cm⁻² in a membrane electrode assembly.

Modulating Microenvironmental pH: The cavity and channel structures of porous materials help create a highly alkaline microenvironment near the catalyst surface, which inhibits the hydrogen evolution reaction and promotes CO₂ conversion. For example, La-doped Cu hollow sphere catalysts with porous channel structures achieved a C₂₊ product Faraday efficiency of 86.2% and a partial current density of −775.8 mA cm⁻² in acidic electrolytes.

Stabilizing Key Intermediates: Porous structures can stabiliz active species, , such as Cu⁺, to enhance the selectivity of C₂₊ products. For example, porous Cu₂O catalysts maintained the characteristic Raman mode of Cu⁺ during electrochemical reduction, with Cu⁺ species content remaining at 32.1% even after 20 minutes of reaction.

Facilitating Mass Transfer and Diffusion: Porous materials can regulate mass transfer processes, improving reaction rates. For instance, a porous Cu catalytic layer prepared by co-sputtering deposition of Cu and Al, followed by dealloying, promoted gas transmission at high current densities, achieving a C₂H₄ partial current density of 420 mA cm⁻² at a low cell voltage.

Tuning the Nature of Active Sites: Porous nanomaterials, as carriers for metal active centers, can regulate the properties of active sites, thus enhancing the performance of eCO₂RR. For example, Ag single atoms anchored on porous concave N-doped carbon achieved a CO Faraday efficiency of 95% at −0.37 V vs. RHE.

This review provides a systematic summary and in-depth insights into the application of porous catalysts in eCO₂RR, identifying current challenges such as the precise fabrication of porous structures, understanding structure-performance relationships, and the feasibility of practical applications. Future research directions include achieving controllable synthesis of porous catalysts, exploring the multiscale effects of porous structures, optimizing catalyst design using theoretical calculations and machine learning, combining emerging characterization techniques to explore reaction mechanisms, and promoting the industrial application of eCO₂RR technology, with a focus on cost, catalytic performance, and product value for economic feasibility and environmental sustainability.

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About the Journal

Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top one journals in Applied Chemistry with a current SCI impact factor of 15.7. The Editors-in-Chief are Profs. Can Li and Tao Zhang.

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