Alkali metal-doped g-C3N4: a multifunctional photocatalytic partner for solar-induced energy conversion and environmental restoration

Abstract

Nanomaterials having distinct structural and optical characteristics have been vastly investigated to achieve solar energy transformations, a crucial pathway towards renewable energy generation and environmental sustainability. Amongst nanostructured g-C3N4 has been identified as a promising candidate owing to its remarkable photocatalytic potential. Notably, incorporating alkali metal ions into the crystal lattice of g-C3N4 serves as an effective strategy to modulate its crystalline structure, enhance photon-harvesting capabilities, improve surface area, and optimize photocatalytic performance, all while retaining environmental compatibility. This review highlights the overview of recent developments in alkali metal doping of g-C3N4, focusing on designing strategy, structural modifications, and the resulting alterations in electronic and physicochemical properties. Considering their low synthesis cost, facile fabrication routes, environmental benignity, and highly tuneable band alignment in alkali metal-doped g-C3N4 nanostructures represent a versatile class of materials with broad potential in advanced photocatalytic applications. DFT calculations, theoretical modelling, and various characterization techniques were systematically reviewed for structure elucidation and optical modification after the alkali metal ion doping in g-C3N4. We also provide concrete case studies by reviewing the structure-activity relationships of various alkali metal-doped g-C3N4-based photocatalysts having potential application in artificial photosynthesis, ranging from solar fuel production, biomass conversion, organic transformation, pollutant degradation, to other miscellaneous applications, mainly supported by the in-depth photocatalytic mechanism.Finally, we conclude and highlight the research gap and future perspectives. We believe this review is intended to serve as a comprehensive reference for both academic researchers and industrial practitioners engaged in the design and development of alkali-doped g-C3N4-based photocatalytic systems.