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Molecular Junction Photocatalysts in Graphitic Carbon Nitride: Precise Characterization of Built-in Electric Fields and Challenges in Spatial Charge Separation
Review Article  ·  Published: 03 April 2026
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Journal of Advanced Materials Research
Volume 2, Issue 2, 2026: 119-141
Review Article Open Access

Molecular Junction Photocatalysts in Graphitic Carbon Nitride: Precise Characterization of Built-in Electric Fields and Challenges in Spatial Charge Separation

by
Kaichi Chen Kaichi Chen 1 ORCID
Zhicheng Zheng Zhicheng Zheng 1
Yukun Fang Yukun Fang 1
Yuanyuan Liu Yuanyuan Liu 2 *
Xinli Guo Xinli Guo 1 * ORCID
1 State Key Laboratory of Engineering Materials for Major Infrastructure, School of Materials Science and Engineering, Southeast University, Nanjing 211189, China
2 School of Chemistry and Chemical Engineering, Xuzhou University of Technology, Xuzhou 221018, China
* Corresponding Authors: Yuanyuan Liu, [email protected]; Xinli Guo, [email protected]
Volume 2, Issue 2
Volume 2, Issue 2 2026
Received: 09 March 2026 Accepted: 27 March 2026 Published: 03 April 2026 CrossMark
Download PDF 21.34 MB Cite Metrics
DOI: 10.62762/JAMR.2026.848022
ARK: ark:/57805/jamr.2026.848022

Article Information

Published in Journal of Advanced Materials Research
Volume/Issue Volume 2, Issue 2, 2026
Pages 119-141
Cited by 4 (Crossref) 4 (Scopus)

Abstract

Graphitic carbon nitride (g-C$_3$N$_4$) has garnered interest as a versatile photocatalytic platform owing to its tailorable electronic architecture; however, its solar-to-chemical conversion is bottlenecked by high exciton binding energies and slow charge-carrier transport. To circumvent these impediments, the construction of ``molecular junctions'' within the conjugated polymeric scaffold enables atomically precise modulation of spatial electron configurations. Unlike conventional heterostructures relying on physical contact, molecular junctions employ robust covalent bridging, facilitating molecular orbital hybridization and $\pi$-conjugation. This review summarizes recent advances in molecular-junction-functionalized g-C$_3$N$_4$ photocatalysts, focusing on built-in electric field (BIEF) induction and its effects on charge-carrier dynamics. Molecular junctions are categorized into homojunctions exploiting structural polymorphisms and heterojunctions incorporating donor–acceptor moieties or single-atom sites. Structural asymmetry engenders steep potential gradients, mitigating exciton binding and promoting unidirectional charge migration. State-of-the-art BIEF characterization techniques—including Kelvin probe force microscopy (KPFM), density functional theory (DFT), and ultrafast transient absorption spectroscopy—are systematically examined. Finally, the catalytic efficacy of these molecular junction paradigms is assessed across solar-driven applications, including photocatalytic hydrogen evolution, overall water splitting, and hydrogen peroxide synthesis. The review concludes by outlining key bottlenecks and future directions, emphasizing atomically precise synthesis and operando characterization.

Graphical Abstract

Molecular Junction Photocatalysts in Graphitic Carbon Nitride: Precise Characterization of Built-in Electric Fields and Challenges in Spatial Charge Separation

Keywords

graphitic carbon nitride molecular junction photocatalysis built-in electric field spatial charge separation

Data Availability Statement

Not applicable.

Funding

This work was financially supported by the Natural Science Foundation of Jiangsu Province, China under Grant BK20240332, and the Big Data Computing Center of Southeast University, China.

Conflicts of Interest

The authors declare no conflicts of interest.

AI Use Statement

The authors declare that no generative AI was used in the preparation of this manuscript.

Ethical Approval and Consent to Participate

Not applicable.

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Chen, K., Zheng, Z., Fang, Y., Liu, Y., & Guo, X. (2026). Molecular Junction Photocatalysts in Graphitic Carbon Nitride: Precise Characterization of Built-in Electric Fields and Challenges in Spatial Charge Separation. Journal of Advanced Materials Research, 2(2), 119–141. https://doi.org/10.62762/JAMR.2026.848022
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TY  - JOUR
AU  - Chen, Kaichi
AU  - Zheng, Zhicheng
AU  - Fang, Yukun
AU  - Liu, Yuanyuan
AU  - Guo, Xinli
PY  - 2026
DA  - 2026/04/03
TI  - Molecular Junction Photocatalysts in Graphitic Carbon Nitride: Precise Characterization of Built-in Electric Fields and Challenges in Spatial Charge Separation
JO  - Journal of Advanced Materials Research
T2  - Journal of Advanced Materials Research
JF  - Journal of Advanced Materials Research
VL  - 2
IS  - 2
SP  - 119
EP  - 141
DO  - 10.62762/JAMR.2026.848022
UR  - https://www.icck.org/article/abs/JAMR.2026.848022
KW  - graphitic carbon nitride
KW  - molecular junction
KW  - photocatalysis
KW  - built-in electric field
KW  - spatial charge separation
AB  - Graphitic carbon nitride (g-C$_3$N$_4$) has garnered interest as a versatile photocatalytic platform owing to its tailorable electronic architecture; however, its solar-to-chemical conversion is bottlenecked by high exciton binding energies and slow charge-carrier transport. To circumvent these impediments, the construction of ``molecular junctions'' within the conjugated polymeric scaffold enables atomically precise modulation of spatial electron configurations. Unlike conventional heterostructures relying on physical contact, molecular junctions employ robust covalent bridging, facilitating molecular orbital hybridization and $\pi$-conjugation. This review summarizes recent advances in molecular-junction-functionalized g-C$_3$N$_4$ photocatalysts, focusing on built-in electric field (BIEF) induction and its effects on charge-carrier dynamics. Molecular junctions are categorized into homojunctions exploiting structural polymorphisms and heterojunctions incorporating donor–acceptor moieties or single-atom sites. Structural asymmetry engenders steep potential gradients, mitigating exciton binding and promoting unidirectional charge migration. State-of-the-art BIEF characterization techniques—including Kelvin probe force microscopy (KPFM), density functional theory (DFT), and ultrafast transient absorption spectroscopy—are systematically examined. Finally, the catalytic efficacy of these molecular junction paradigms is assessed across solar-driven applications, including photocatalytic hydrogen evolution, overall water splitting, and hydrogen peroxide synthesis. The review concludes by outlining key bottlenecks and future directions, emphasizing atomically precise synthesis and operando characterization.
SN  - 3070-5851
PB  - Institute of Central Computation and Knowledge
LA  - English
ER  -
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@article{Chen2026Molecular,
  author = {Kaichi Chen and Zhicheng Zheng and Yukun Fang and Yuanyuan Liu and Xinli Guo},
  title = {Molecular Junction Photocatalysts in Graphitic Carbon Nitride: Precise Characterization of Built-in Electric Fields and Challenges in Spatial Charge Separation},
  journal = {Journal of Advanced Materials Research},
  year = {2026},
  volume = {2},
  number = {2},
  pages = {119-141},
  doi = {10.62762/JAMR.2026.848022},
  url = {https://www.icck.org/article/abs/JAMR.2026.848022},
  abstract = {Graphitic carbon nitride (g-C\$\_3\$N\$\_4\$) has garnered interest as a versatile photocatalytic platform owing to its tailorable electronic architecture; however, its solar-to-chemical conversion is bottlenecked by high exciton binding energies and slow charge-carrier transport. To circumvent these impediments, the construction of ``molecular junctions'' within the conjugated polymeric scaffold enables atomically precise modulation of spatial electron configurations. Unlike conventional heterostructures relying on physical contact, molecular junctions employ robust covalent bridging, facilitating molecular orbital hybridization and \$\pi\$-conjugation. This review summarizes recent advances in molecular-junction-functionalized g-C\$\_3\$N\$\_4\$ photocatalysts, focusing on built-in electric field (BIEF) induction and its effects on charge-carrier dynamics. Molecular junctions are categorized into homojunctions exploiting structural polymorphisms and heterojunctions incorporating donor–acceptor moieties or single-atom sites. Structural asymmetry engenders steep potential gradients, mitigating exciton binding and promoting unidirectional charge migration. State-of-the-art BIEF characterization techniques—including Kelvin probe force microscopy (KPFM), density functional theory (DFT), and ultrafast transient absorption spectroscopy—are systematically examined. Finally, the catalytic efficacy of these molecular junction paradigms is assessed across solar-driven applications, including photocatalytic hydrogen evolution, overall water splitting, and hydrogen peroxide synthesis. The review concludes by outlining key bottlenecks and future directions, emphasizing atomically precise synthesis and operando characterization.},
  keywords = {graphitic carbon nitride, molecular junction, photocatalysis, built-in electric field, spatial charge separation},
  issn = {3070-5851},
  publisher = {Institute of Central Computation and Knowledge}
}

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CC BY Copyright © 2026 by the Author(s). Published by Institute of Central Computation and Knowledge. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.
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