Coordination structure of Cu for photocatalytic production of C1 chemicals from glucose

Lignocellulosic biomass is the largest renewable carbon resource on earth. Cellulose and hemicellulose, featuring polymeric carbohydrate structure, are important components of lignocellulose. Refinery of the carbohydrates to target products remains a major challenge for their valorization. One solution is fully breaking the C‒C bonds, so the carbohydrates are converted to C₁ chemicals, such as CO and HCOOH.

Photocatalysis on semiconductors can generate oxidative holes that can activate chemical bonds theoretically. The radical mechanism can circumvent the formation of humins that are formed via the recondensation of carbohydrates via the carbocation or carbanion mechanism. Glucose is photo-oxidized by TiO₂-based photocatalysts to break the C‒C bond and the main liquid products range from C₁ to multi-carbon compounds, which raises the problem of separating products. Besides, the gas-phase carbon-containing products are mainly low-value CO₂. Photocatalytic glucose decomposition produces the gas-phase product, such as syngas (CO and H₂). The challenge of product separation will be alleviated and the product value will be maximized. Previously, Feng Wang's group achieved the decomposition of polyols and sugars to CO and H₂ with a CO selectivity of 90%. The Cu^δ+ atomically dispersed on TiO₂ originates oxygen vacancies that activate hydroxyl groups of polyols and sugars, so the C‒C bond can be broken via β-scission. However, the positively charged Cu^δ+ can be reduced to metallic Cu and form clusters, so the active structures disappear. Therefore, stabilizing atomically dispersed Cu^δ+ on TiO₂ is a prerequisite for photocatalytic glucose decomposition to C₁ chemicals.

Recently, a research team led by Dr. Nengchao Luo from Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and Dr. Taifeng Liu from Henan University, China, reported that by nitrogen doping into TiO₂, the supported Cu is stabilized because of the electronic interaction between Cu and nitrogen ions. Even under photoirradiation, the atomically dispersed Cu can maintain the Cu⁺ states without aggregation. Because of the nitrogen doping, the valence band structure and defect levels of the Cu/TiO₂ transits to band structures containing N 2p, originating oxidative catalytic sites distinct from Cu/TiO₂. The charge separation efficiency is thus enhanced, resulting in enhanced activity of the photocatalytic glucose decomposition that generates C₁ chemicals (HCOOH and CO) and H₂ with productivities of 1.97 and 2.82 mmol g^-1, respectively, which are 2.1 and 1.7 times that of Cu/TiO₂. This work provides a reference for the design of stabilized Cu-based catalysts for biomass conversion. The results were published in Chinese Journal of Catalysis (https://doi.org/10.1016/S1872-2067(24)60098-7).

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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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