物理化学学报 >> 2025, Vol. 41 >> Issue (9): 100116.doi: 10.1016/j.actphy.2025.100116

所属专题： 光催化中的S型异质结

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碳量子点/TiO2 S型异质结的能带和吸附工程促进光催化CO2甲烷化

王文龙1,2, 郝文韬2,3, 何浪2,*(), 乔佳2, 李宁1,*(), 陈朝秋2,*(), 覃勇2   

  1. 1 中北大学能源与动力工程学院, 煤与煤层气共采全国重点实验室, 山西 太原 030051
    2 中国科学院山西煤炭化学研究所, 煤炭高效低碳利用全国重点实验室, 山西 太原 030001
    3 中国科学院大学, 北京 10049
  • 收稿日期:2025-04-27 修回日期:2025-06-09 录用日期:2025-06-10 发布日期:2025-07-04
  • 通讯作者: Email: helang@sxicc.ac.cn (何浪)lnlong2834@yeah.net (李宁)chenchaoqiu@sxicc.ac.cn (陈朝秋)
  • 基金资助:
    国家自然科学基金(22372190); 中国科学院山西煤炭化学研究所(SCJC-2023-20); 山西省科技创新人才团队(领军)专项基金(202304051001007); 2023年度国家资助博士后研究人员计划(C档)(GZC20232815); 中国博士后科学基金(2024M753358); 中国博士后科学基金(2024M763394)

Bandgap and adsorption engineering of carbon dots/TiO2 S-scheme heterojunctions for enhanced photocatalytic CO2 methanation

Wenlong Wang1,2, Wentao Hao2,3, Lang He2,*(), Jia Qiao2, Ning Li1,*(), Chaoqiu Chen2,*(), Yong Qin2   

  1. 1 School of Energy and Power Engineering & State Key Laboratory of Coal and CBM Co-Mining, North University of China, Taiyuan 030051, Shanxi Province, China
    2 State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, Shanxi Province, China
    3 University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2025-04-27 Revised:2025-06-09 Accepted:2025-06-10 Published:2025-07-04
  • Contact: Email: helang@sxicc.ac.cn (Lang He)lnlong2834@yeah.net (Ning Li)chenchaoqiu@sxicc.ac.cn (Chaoqiu Chen)
  • Supported by:
    the National Natural Science Foundation of China(22372190); ICC CAS(SCJC-2023-20); the special fund for Science and Technology Innovation Teams of Shanxi Province(202304051001007); the Postdoctoral Fellowship Program of CPSF(GZC20232815); China Postdoctoral Science Foundation(2024M753358); China Postdoctoral Science Foundation(2024M763394)

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摘要：

S型异质结光催化剂因同时具有优异的光生载流子分离效率和较强的氧化还原能力，而被广泛应用于光催化二氧化碳(CO2)还原制高价值化学品(如甲烷)中。碳量子点(Carbon dots，CDs)材料具有能带结构和吸光范围可调的独特优势，可与常用半导体材料(如氧化钛，TiO 2)形成有效S型异质结光催化剂。然而，碳量子点能带结构和表面吸附性质在调控CDs/TiO2的异质结构型、载流子分离和传输动力学、以及CO2活化和还原产物选择性中的重要作用仍缺乏深入研究。本文通过改变CDs的碳源，包括低阶煤沥青(C-GQDs，1.75 nm)、葡萄糖(G-CQDs，1.84 nm)、丙酮(CQDs-X，1.82 nm)和炭黑(GQDs-A，1.92 nm)，构建了四种CDs/TiO2异质结光催化剂，并将其用于光催化CO2甲烷化反应。研究发现，CDs/TiO2异质结类型、光生电荷载流子的转移路径、迁移和分离效率、CO2的吸附和活化能力以及还原产物的选择性与CDs的能带结构和表面吸附性质密切相关。CDs的引入显著增强了TiO2光利用的能力，其中，以低价煤沥青为碳源构建的C-GQDs/TiO2 S型异质结具有最高的CH4生成速率，达到32.7 μmol·g−1·h−1，是单一TiO2的6.3倍，并且显著高于其它三种异质结，分别是GQDs-A/TiO2、CQDs-X/TiO2和G-CQDs/TiO2的3.8、2.7和2.3倍。该催化剂还具有72.6%的高电子基CH4选择性和98.1%的烃类产物选择性(CH4，C2H6，C2H4和C3H8)。相反地，其它三种碳源CDs(GQDs-A、CQDs-X和G-CQDs)的引入导致CH4选择性大幅下降(均小于40.0%)。原位XPS和程序升温脱附实验结果表明，C-GQDs/TiO2高的甲烷生成速率和选择性可归因于其独特的S型异质结结构、较高的还原电势和匹配的CO2和H2O吸附活化能力。这项研究为CDs/TiO2光催化剂在S型异质结电子传递途径的驱动下将CO2高效光还原为CH4提供了独特的见解。

关键词: 能带工程, CDs/TiO2, S型异质结, 光催化CO2甲烷化, 煤基碳量子点

Abstract:

S-scheme heterojunctions have garnered significant interest in photocatalytic CO2 conversion to valuable products (e.g., CH4) due to their enhanced charge separation and robust redox capabilities. Carbon dots (CDs), with their tunable band structures and light absorption ranges, show particular promise in constructing efficient S-scheme photocatalytic systems. Nevertheless, the critical roles of CDs' band alignment and surface adsorption properties in determining heterojunction configuration, charge carrier kinetics, and ultimately CO2 activation/product selectivity distribution remain insufficiently explored. Herein, we construct four CDs/TiO2 heterojunctions using CDs synthesized from varied carbon sources, in which S-scheme heterojunctions were successfully constructed based on cost-effective coal pitch (C-GQDs, 1.75 nm), glucose (G-CQDs, 1.84 nm), and acetone (CQDs-X, 1.82 nm) carbon sources, whereas Type-Ⅰ heterojunctions were formed by carbon black based CDs (GQDs-A, 1.92 nm). Systematic investigations reveal that both the band structure and adsorption characteristics of CDs play important roles in the charge transfer path and separation efficiency, CO2 adsorption and activation capacities, and product selectivity in photocatalytic CO2 reduction. Remarkably, the introduction of CDs significantly broadens the photo-response range compared to fresh TiO2, and in particular, the C-GQDs/TiO2 exhibits exceptional performance with a CH4 production rate of 32.7 μmol·g−1·h−1, surpassing TiO2 by 6.3-fold and outperforming GQDs-A/TiO2, CQDs-X/TiO2, and G-CQDs/TiO2 by factors of 3.8, 2.7, and 2.3, respectively. This heterojunction simultaneously achieves 72.6% CH4 selectivity and 98.1% hydrocarbons selectivity (encompassing CH4, C2H6, C2H4, and C3H8). In contrast, composites incorporating GQDs-A, CQDs-X, or G-CQDs exhibit substantially diminished CH4 selectivity (< 40.0%). The high CH4 production rate and selectivity of C-GQDs/TiO2 can be attributed to its unique S-scheme heterojunction structure, higher reduction potential, and well-matched CO2 and H2O adsorption and activation capabilities. This study provides unique insights into the efficient photoreduction of CO2 to CH4 driven by the S-scheme heterojunction electron transfer pathway in CDs/TiO2 photocatalysts.

Key words: Bandgap engineering, Carbon dots/TiO2, S-scheme heterojunctions, Photocatalytic CO2 methanation, Coal-based carbon dots