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20. Synthesis, Characterization, and Roles of Vacancy Defects in Polymer and Graphitized Carbon Nitride Photocatalysts: A Comprehensive Review.

Author

Pundi, Arul and Chang, Chi-Jung

Subjects
*OXYGEN vacancy, *ELECTRONIC band structure, *BAND gaps, *CHARGE carriers, *PHOTOCATALYSTS, *POLYIMIDES
Abstract

Vacancy defect graphitic carbon nitride (g-C3N4) and conjugated polyimide (PI) polymer photocatalysts have become increasingly recognized as metal-free photocatalysts featuring an appropriate bandgap. The narrow absorption spectrum of visible light and the rapid recombination rate of the photoexcited charge carriers in PI polymers and g-C3N4 impede its photocatalytic performance. The presence of oxygen vacancies (OVs) in PI polymer photocatalysts, as well as nitrogen vacancies (NVs) and carbon vacancies (CVs) in g-C3N4, can significantly enhance the migration of photogenerated electrons. Adding vacancies to improve the electronic structure and band gap width can greatly enhance the photocatalytic efficiency of PI polymers and g-C3N4. Defect engineering is important for increasing the photocatalytic ability of PI-polymer and g-C3N4. There remains a notable absence of thorough review papers covering the synthesis, characterization, and applications of vacancy-rich PI-polymer and g-C3N4 in photocatalysis. This review paper examines the roles of OVs in PI-polymer, NVs, and CVs in g-C3N4 and thoroughly summarizes the preparation approaches employed before and after, as well as during polymerization. This review scrutinizes spectroscopic characterization techniques, such as EPR, XPS, PAS, XRD, FTIR, and NMR, for vacancy defect analysis. We also reviewed the role of vacancies, which include light absorption, photogenerated charge carrier separation, and transfer dynamics. This review could serve as a comprehensive understanding, a vacancy-engineered design framework, and a practical guide for synthesizing and characterizing. [ABSTRACT FROM AUTHOR]

Published
2025
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35. Effect of Calcination-Induced Oxidation on the Photocatalytic H 2 Production Performance of Cubic Cu 2 O/CuO Composite Photocatalysts.

Author

Chang, Chi-Jung, Kang, Chun-Wen, and Pundi, Arul

Subjects
*OXYGEN vacancy, *HYDROGEN production, *PHOTOCATALYSTS, *LIGHT absorption, *LACTIC acid
Abstract

This study explores the H2 production performance of CuO/Cu2O with different morphology (nanocubes) synthesized by different methods using different sacrificial reagent (lactic acid), compared with the other three reported CuO/Cu2O photocatalysts used for H2 production. A cubic Cu2O photocatalyst was prepared using a hydrothermal method. It was then calcined at a certain temperature to form a cubic Cu2O/CuO composite photocatalyst. XRD, TEM, and XPS spectra confirmed the successful synthesis of cubic Cu2O/CuO composite photocatalysts by calcination-induced oxidation at a certain temperature. As the calcination temperature increases, the crystal phase of the photocatalyst changes from Cu2O to Cu2O/CuO and then to CuO. The effects of calcination-induced oxidation on morphology, light absorption, the separation of photoexcited carriers, and the H2 production activity of photocatalysts were studied. EPR spectra were monitored to analyze the oxygen vacancies in different samples. Mott–Schottky and Tauc plots were utilized to establish the band structure of the composite photocatalyst. Cu2O/CuO is a type II photocatalyst with a heterogeneous structure that helps to improve electron–hole separation efficiency. The H2 production efficiency of Cu2O/CuO composite photocatalyst reaches 11,888 μmol h−1g−1, 1.6 times that of Cu2O. The formation of the Cu2O/CuO heterojunction leads to enhanced light absorption, charge separation, and hydrogen production activity. [ABSTRACT FROM AUTHOR]

Published
2024
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