Chlorophyll-Based Organic Heterojunction on Ti3 C2 Tx MXene Nanosheets for Efficient Hydrogen Production

Squaraine dye/Ti3C2Tx MXene organic-inorganic hybrids for photocatalytic hydrogen evolution

MXenes, a new family of 2D nanostructured materials, have been widely studied in the field of artificial photosynthesis due to their outstanding physicochemical properties. In this work, a series of 2,4-bis[4-(N,N-dibutylamino)phenyl] squaraine (SQ) derivatives with different number of hydroxyl groups were hybridized with Ti₃C₂T_x MXene nanosheets, and the organic-inorganic hybrid photocatalysts were applied for water-splitting hydrogen evolution. The mass ratios of SQ@Ti₃C₂T_x were optimized to 4 wt% for each SQ, and the best hydrogen evolution reaction (HER) rate of 28.6 μmol h^-1 g^-1 was achieved by SQ-3 with four OH groups. The photocatalytic ability of the hybrid comes from the outstanding light harvesting of SQ dye, sufficient active sites of Ti₃C₂T_x, and efficient separation and transfer of the photogenerated charges via heterojunction between SQ aggregates and Ti₃C₂T_x. This work firstly demonstrates an example of SQ sensitizer combined with MXene for hydrogen generation, which provides a new insight to further explore the MXene-based hybrid nanomaterials for water splitting hydrogen evolution.

Biohybrid Molecule-Based Photocatalysts for Water Splitting Hydrogen Evolution

The problems of resource depletion and environmental pollution caused by the excessive use of fossil fuels greatly restrict the rapid development of human technology and industry, which has led to a high demand for the development of new and clean energy sources. Hydrogen, due to its high calorific value and environmentally friendly combustion products, is undoubtedly a very promising energy carrier. The current methods of industrial hydrogen production are mainly water electrocatalytic decomposition or fossil fuels conversion, which also results in the waste of other energy sources. Since only one-step is involved during the conversion from solar to chemical energy and thus unnecessary energy waste is avoided, solar energy photocatalytic decomposition of water provides a more viable method for hydrogen production. The utilization of biohybrid molecules, which are widely available in nature and environmentally friendly, further reduce the cost of such photocatalytic systems. This Review discusses the research progress on hydrogen production using biohybrid molecules for photocatalytic hydrogen evolution. The basic reaction mechanism, general types and system structures about biohybrid molecule-based photocatalysts are summarized. The current challenges and prospects in the research of water splitting hydrogen evolution by biohybrid molecules photocatalysts are presented.

A Review on MXene Synthesis, Stability, and Photocatalytic Applications

Photocatalytic water splitting, CO₂ reduction, and pollutant degradation have emerged as promising strategies to remedy the existing environmental and energy crises. However, grafting of expensive and less abundant noble-metal cocatalysts on photocatalyst materials is a mandatory practice to achieve enhanced photocatalytic performance owing to the ability of the cocatalysts to extract electrons efficiently from the photocatalyst and enable rapid/enhanced catalytic reaction. Hence, developing highly efficient, inexpensive, and noble-metal-free cocatalysts composed of earth-abundant elements is considered as a noteworthy step toward considering photocatalysis as a more economical strategy. Recently, MXenes (two-dimensional (2D) transition-metal carbides, nitrides, and carbonitrides) have shown huge potential as alternatives for noble-metal cocatalysts. MXenes have several excellent properties, including atomically thin 2D morphology, metallic electrical conductivity, hydrophilic surface, and high specific surface area. In addition, they exhibit Gibbs free energy of intermediate H atom adsorption as close to zero and less than that of a commercial Pt-based cocatalyst, a Fermi level position above the H₂ generation potential, and an excellent ability to capture and activate CO₂ molecules. Therefore, there is a growing interest in MXene-based photocatalyst materials for various photocatalytic events. In this review, we focus on the recent advances in the synthesis of MXenes with 2D and 0D morphologies, the stability of MXenes, and MXene-based photocatalysts for H₂ evolution, CO₂ reduction, and pollutant degradation. The existing challenges and the possible future directions to enhance the photocatalytic performance of MXene-based photocatalysts are also discussed.

Ti3C2Tx MXene nanosheets hybridized with bacteriochlorin–carotenoid conjugates for photocatalytic hydrogen evolution

Development of efficient photocatalysts with a wide spectral range for the photocatalytic hydrogen evolution reaction (HER) is a promising way to address the current energy and environmental crises.