As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Semiconductor-based photocatalysis is considered to be an attractive way for solving the worldwide energy shortage and environmental pollution issues. Since the pioneering work in 2009 on graphitic carbon nitride (g-C3N4) for visible-light photocatalytic water splitting, g-C3N4 -based photocatalysis has become a very hot research topic. This review summarizes the recent progress regarding the design and preparation of g-C3N4 -based photocatalysts, including the fabrication and nanostructure design of pristine g-C3N4 , bandgap engineering through atomic-level doping and molecular-level modification, and the preparation of g-C3N4 -based semiconductor composites. Also, the photo-catalytic applications of g-C3N4 -based photocatalysts in the fields of water splitting, CO2 reduction, pollutant degradation, organic syntheses, and bacterial disinfection are reviewed, with emphasis on photocatalysis promoted by carbon materials, non-noble-metal cocatalysts, and Z-scheme heterojunctions. Finally, the concluding remarks are presented and some perspectives regarding the future development of g-C3N4 -based photocatalysts are highlighted.

Polymeric Photocatalysts Based on Graphitic Carbon Nitride

A review on g-C3N4-based photocatalysts

Photocatalysis is considered as one of the promising routes to solve the energy and environmental crises by utilizing solar energy. Graphitic carbon nitride (g-C3N4) has attracted worldwide attention due to its visible-light activity, facile synthesis from low-cost materials, chemical stability, and unique layered structure. However, the pure g-C3N4 photocatalyst still suffers from its low separation efficiency of photogenerated charge carriers, which results in unsatisfactory photocatalytic activity. Recently, g-C3N4-based heterostructures have become research hotspots for their greatly enhanced charge carrier separation efficiency and photocatalytic performance. According to the different transfer mechanisms of photogenerated charge carriers between g-C3N4 and the coupled components, the g-C3N4-based heterostructured photocatalysts can be divided into the following categories: g-C3N4-based conventional type II heterojunction, g-C3N4-based Z-scheme heterojunction, g-C3N4-based p–n heterojunction, g-C3N4/metal heterostructure, and g-C3N4/carbon heterostructure. This review summarizes the recent significant progress on the design of g-C3N4-based heterostructured photocatalysts and their special separation/transfer mechanisms of photogenerated charge carriers. Moreover, their applications in environmental and energy fields, e.g., water splitting, carbon dioxide reduction, and degradation of pollutants, are also reviewed. Finally, some concluding remarks and perspectives on the challenges and opportunities for exploring advanced g-C3N4-based heterostructured photocatalysts are presented.

g-C3N4-Based Heterostructured Photocatalysts

S-Scheme Heterojunction Photocatalyst

The transfer mechanism of photogenerated charges (e– and h⁺) has always been a research hotspot of the photocatalysis field. Here, a series of WO₃/ZnO composite photocatalysts with different ratios were synthesized, and importantly, the transfer mechanism of photoexcited charges was systematically studied. By performing various characterizations, the direct Z-scheme of WO₃/ZnO was proposed, and the results verified that the immanent electric field formed between WO₃ and ZnO semiconductors is the inner impetus of charge transfer. This work distinguished the transfer mechanism of photogenerated charges in the heterojunction photocatalyst by the relative p–n junction theory and can also provide guidance for the construction and application of novel heterojunction photocatalysts in theory and practice.

Investigation on the Mechanism and Inner Impetus of Photogenerated Charge Transfer in WO₃/ZnO Heterojunction Photocatalysts

Construction of TiO2 nanosheets with exposed {0 0 1} facets/Zn0.2Cd0.8S-DETA heterostructure with enhanced visible light hydrogen production

Construction of CoTiO3/BiOI p-n heterojunction with nanosheets-on microrods structure for enhanced photocatalytic degradation of organic pollutions

LSPR-enhanced carbon-coated In2O3/W18O49 S-scheme heterojunction for efficient CO2 photoreduction

ZnO nanorod arrays were fabricated on glass through hydrothermal way. Then a thin SiO2 film were covered on ZnO nanorod arrays using pulsed laser deposition (PLD) technique, and modified by stearic acid. It is found that SiO2 film only had slight effects on the contact angle and transmittance of ZnO nanorod arrays on glass substrate. However, it has brought a huge improvement in the UV durability of superhydrophobic ZnO nanorod arrays. The results showed that the water contact angle remains constant at 160.5o even UV irradiation time exceeded 50 h when the deposition time of PLD is about 10 min. This structure with UV-durable superhydrophobicity and highly transmittance on glass substrate can be served as front materials in solar cells.

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Jinfeng Zhang

Papers

Investigation on the Mechanism and Inner Impetus of Photogenerated Charge Transfer in WO₃/ZnO Heterojunction Photocatalysts

Construction of TiO2 nanosheets with exposed {0 0 1} facets/Zn0.2Cd0.8S-DETA heterostructure with enhanced visible light hydrogen production

Construction of CoTiO3/BiOI p-n heterojunction with nanosheets-on microrods structure for enhanced photocatalytic degradation of organic pollutions

LSPR-enhanced carbon-coated In2O3/W18O49 S-scheme heterojunction for efficient CO2 photoreduction

SiO2 Coated on ZnO Nanorod Arrays With UV-Durable Superhydrophobicity and Highly Transmittance on Glass.