Engineered Photocatalytic Nanomaterials: Configurations, Functional Heterojunctions, and Emerging Strategies

Photocatalysis has been a proven magnanimous scientific methodology for a wide array of real-world solutions. The highlights of the broad domain include environmental remediation, synthesis and decomposition of organic molecules, and, more recently, the splitting of water and biomolecules for concurrent generation of green hydrogen and value-added chemicals. Along with significant enhancement in the yield of green hydrogen, the photocatalytic oxidation of biomass and bio-derived compounds has been providing numerous pathways for the generation of specialty chemicals such as formic acid, glycolic acid, 5-hydroxymethylfurfural (HMF), 2,5-diformylfuran (DFF), and 2,5furandicarboxylic acid (FDCA). Photocatalysis enables the use of a broad spectrum of solar energy, including the ultraviolet, visible, and infrared wavelengths, along with synthetic radiations such as xenon and mercury lamps. Photocatalysis has been a conventional technology for treatment of aqueous waste streams arising from industries, municipal areas, and medical sources, along with additional treatment of fresh water for potable use. Nano-scale composite structures with tailored heterojunction designs aim at maximizing the generation and irreversible transfer of charge carriers in a synergistic manner. The unique attributes of nanocomposites for efficient photo-generation of electrons and holes arise from the tailored modulation of properties such as surface area, size and anisotropy, crystallinity, dimensionality, and tunable electronic structure. The present review covers the key nanomaterials and nanocomposites with proven performance in photocatalysis, the mechanism of light absorption and charge transfer, and advanced heterojunction strategies for enhancement of photocatalytic efficiency.The review highlights the established and emerging design approaches mediated by nanomaterials and efficient pathways for creating high-performing heterojunctions. Further, the current advances and future perspectives present the focus on developing cost-effective, visible-light-responsive, and environmentally benign photocatalytic systems for large-scale applications.