Research on mechanism of catalytic reduction of CO2 by alkali-heat treated SnO2/g-C3N4

SU Mingxue; GU Chunhan; ZHANG Han; LI Ning

doi:10.13205/j.hjgc.202602017

Volume 44 Issue 2

Feb. 2026

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SU Mingxue, GU Chunhan, ZHANG Han, LI Ning. Research on mechanism of catalytic reduction of CO2 by alkali-heat treated SnO2/g-C3N4[J]. ENVIRONMENTAL ENGINEERING , 2026, 44(2): 150-157. doi: 10.13205/j.hjgc.202602017

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SU Mingxue, GU Chunhan, ZHANG Han, LI Ning. Research on mechanism of catalytic reduction of CO₂ by alkali-heat treated SnO₂/g-C₃N₄[J]. ENVIRONMENTAL ENGINEERING , 2026, 44(2): 150-157. doi: 10.13205/j.hjgc.202602017

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Research on mechanism of catalytic reduction of CO₂ by alkali-heat treated SnO₂/g-C₃N₄

doi: 10.13205/j.hjgc.202602017

SU Mingxue^1,2,
GU Chunhan^1,2,
ZHANG Han^1,2,
LI Ning^1,2

1. Hefei Cement Research & Design Institute Corporation Ltd., Hefei 230022, China;
2. Anhui Key Laboratory of Green and Low-Carbon Technology in Cement Manufacturing, Hefei 230022, China

Received Date: 2025-05-08
Available Online: 2026-04-11
Publish Date: 2026-02-01

Abstract

Abstract

Electrocatalytic reduction of CO₂ （eCO₂RR） is a crucial pathway for China to achieve its "Carbon Peak and Carbon Neutrality" goals. Graphitic carbon nitride （g-C₃N₄） is widely employed as a catalyst or catalyst support in electrocatalysis due to its abundant raw materials， simple preparation process， and low cost. However， g-C₃N₄， when used as a catalyst support for eCO₂RR， faces bottlenecks such as low specific surface area， weak alkalinity， and competitive reduction of low-concentration CO₂ and O₂ in actual flue gas. Therefore， this study proposed a modification strategy for SnO₂/g-C₃N₄ composite catalysts through alkali-thermal treatment. Characterization techniques such as XPS and CO₂-TPD revealed that the alkali-thermal treatment significantly increased the surface amino group content of the g-C₃N₄ support （from 3.7% to 7.0%）， enhancing the overall alkalinity and CO₂ adsorption capacity of the catalyst （from 7.69 mmol/g to 48.80 mmol/g）. This treatment accelerated electron transfer from N atoms in g-C₃N₄ to Sn active sites， forming electron-rich Sn centers and generating more oxygen vacancies. These effects synergistically promoted the activation and reduction of CO₂. Competitive adsorption experiments demonstrated that SnO₂/CNOHHT exhibited a higher adsorption capacity for CO₂ than for O₂ in a CO₂/O₂ mixture （with a separation factor of 0.90）. This selectivity favors the formation of a CO₂-enriched microenvironment at the reaction interface， thereby suppressing the competitive oxygen reduction reaction （ORR）. Electrocatalytic performance tests showed that under a pure CO₂ atmosphere， SnO₂/CNOHHT achieved a high Faradaic efficiency （FE） of 80.5% for formate production at a current density of 23.5 mA/cm². Remarkably， in a simulated flue gas atmosphere containing 4% O₂， it still maintained a FE for formate of 59.4%， significantly outperforming both the unmodified and the alkali-treated-only catalysts. This study provides new insight for developing g-C₃N₄-based eCO₂RR catalysts suitable for practical oxygen-containing flue gas conditions.
- CO₂ electroreduction,
- SnO₂,
- graphitic carbon nitride,
- flue gas,
- mass transfer enhancement

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References(25)

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