Photocatalytic hydrogen generation through the utilization of the Ti 3 C 2 MXene photocatalyst offers the best alternatives to provide clean, sustainable, and renewable energy sources. The unique structure, good metallic conductivity, and excellent photochemical properties exhibited by Ti 3 C 2 MXene nominate it as a highly favored cocatalyst to derive hydrogen generation compared to other noncommercial semiconductors. This review highlights the role of Ti 3 C 2 MXene and its potential in promoting photocatalytic hydrogen production through the formation of Schottky interfaces. First, the structural overview and the basic principles of Ti 3 C 2 MXene in photocatalysis are summarized. Second, a brief introduction to the characteristics of Ti 3 C 2 MXene is made to give a firm understanding of its optoelectronic and electrical properties and its stability under thermal and oxidative treatment. Besides, the role of Ti 3 C 2 MXene in promoting photocatalytic hydrogen production is consistently discussed with a focus on the photoactivity enhancement of Ti 3 C 2 MXene-based Schottky junctions. Furthermore, insights into the different morphological effects of Ti 3 C 2 MXene on photocatalytic reactions are summarized. Finally, the future prospects and challenges are discussed to give insights into the future development of Ti 3 C 2 MXene. Hence, this review provides a significant overview for further exploring the role of Ti 3 C 2 MXene as an effective cocatalyst for photocatalytic H 2 production and other energy applications.

Efficient nanomaterials are in high demand in photocatalytic applications to maximize solar energy conversion to renewable fuels. There is growing research on the use of metals as cocatalysts to promote photocatalyst efficiency, but they are expensive. Recently, titanium carbide (Ti3C2T x ) MXenes as layered materials have attracted attention to investigate energy conversion applications. The distinguishing characteristics of Ti3C2T x are higher specific surface area, tunable terminal functional groups (−OH, −O, and −F), exposed metallic active sites, and excellent electrical conductivity. MXenes can be combined with other semiconductors as cocatalysts to improve charge carrier separation. This review discusses various synthesis routes to fabricate Ti3C2T x MXenes as single materials, their surface functionalization, and as cocatalysts to construct a heterojunction for photocatalytic CO2 conversion and H2 production. The different synthesis approaches, such as the HF, halogen, alkali, molten salt, and electrochemical etching routes, to regulate structure, morphology, and efficiency are systematically described. Moreover, synthesis of various morphologies of Ti3C2T x MXenes in terms of dimensions, sizes, and their effect on the performance of energy conversion reactions are systematically discussed. Furthermore, various synthesis routes with regard to fabrication of Ti3C2T x MXene-based nanocomposites for stimulating photocatalytic efficiency with solar energy is elaborated on. The critical analysis and discussion is included on select suitable structures and morphologies of MXenes as cocatalysts and as a support to stimulate the energy harvesting efficiency. Finally, a discussion related to challenges and further developments for exploring pathways in the contexts of synthesis and production of promising renewable fuels is presented.

Excessive release of greenhouse gas carbon dioxide (CO2) into the atmosphere and continuous utilization of fossil fuels has resulted in global warming and energy shortage. Among the different alternatives, photocatalytic conversion of CO2 to fuels and hydrogen production is a promising approach. To achieve this goal, highly efficient and low-cost semiconductor are demanding to maximize solar energy conversion to renewable fuels. In this perspective, metal free two-dimensional (2D) graphitic carbon nitride (g-C3N4) has attracted numerous considerations because of its low cost and higher reduction potential, but it has a lower efficiency. Herein, we demonstrated various engineering defect strategies in g-C3N4 to promote photocatalytic efficiency under solar energy. Initially, an overview of engineering defects, creation of different vacancies in g-C3N4, and their identification is discussed. In the main stream defect, engineering such as carbon, nitrogen, and oxygen to promote g-C3N4 photocatalytic efficiency is systematically disclosed. Subsequently, the role of sulfur (S) and phosphorus (P) atoms in g-C3N4 to maximize CO2 reduction and hydrogen production are deliberated. The comparative analysis, efficiency enhancement, and role of defect engineering are finally discussed to get higher yields and productivities under solar energy utilization.

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Layered double hydroxides (LDHs) have received scientific attractions due to their unique two-dimensional (2D) structure, band gap tunability, and compositional flexibility, leading to the facile incorporation of the metal species into their layered structure. The main objective of this review is to explore the current advancement of LDH-based photocatalysts for photocatalytic hydrogen production by focusing on the role of divalent and trivalent metal incorporations and their efficiency enhancement. Firstly, the mechanism of photocatalysis and its thermodynamics has been explicated to gain basic understanding and fundamentals. Secondly, a brief introduction to the overview of LDH photocatalysts with special attention to the effects of cationic incorporations on the optical properties and computational study towards the electronic density has been demonstrated. Besides, the thermal stability of LDH is briefly discussed, focusing on the effects of temperature towards the conversion into mixed-metal oxide (MMO). Next, the classification of LDH based on divalent and trivalent cationic elements and their role in the brucite layer of LDH are systematically discussed. Attention is given to the mechanistic properties of the extensively studied metals, such as Mg, Ni, Zn, Co, Cr, Fe, V and Al, with the efficiency enhancements through various engineering aspects are demonstrated. The overview summary on the efficient design of LDH is elucidated to provide a deep understanding for improving their photocatalytic properties. Lastly, the future perspectives and recommendations are discussed to provide new insight into the potential of LDH and render them a notable place in solar energy applications.