Titanium Carbide MXenes Cocatalyst with Graphitic Carbon Nitride for Photocatalytic H₂ Production, CO₂ Reduction, and Reforming Applications: A Review on Fundamentals and Recent Advances

Abstract

Two-dimensional (2D) titanium carbide (Ti3C2) MXenes have gained increasing attention in photocatalytic applications due to their prominent electrical conductivity, optical properties, and abundant surface functional groups. The unique layered microstructure characteristics of Ti3C2 provide a large surface area, interlayer spacing, and hydrophilic surface functional groups, contributing to their high photocatalytic efficiency. Graphitic carbon nitride is very promising among the semiconductors due to its layered structure and higher reduction potential. The present study discusses the recent advances in various Ti3C2 structures coupled with g-C3N4 for hydrogen evolution reactions (HER), photocatalytic CO2 reduction reactions (CO2 RR), and CO2 reforming of methane (CO2 RM). Initially, we provide an overview of the fundamental properties of Ti3C2-based composites and recent synthesis approaches, including structure development, of functional group formation, and various etching agents. We further explore using Ti3C2 in different structures coupled with g-C3N4 as a binary and ternary composite with the involvement of other semiconductors and sensitizers. The performance of various composites for water splitting to produce hydrogen and reforming systems, including CO2 conversion with H2O, CO2 methanation, dry reforming of CH4 (DRM), and bireforming of CH4 (BRM), is discussed in detail. The hydrophilic surface functional groups and efficient electron transport pathways of Ti3C2 MXenes make them excellent candidates for catalysts with high yield rates and selectivity. Finally, this review provides valuable insights into the potential applications of Ti3C2-based composites, and future research directions in this field are proposed.

Selective Integrating Molecular Catalytic Units into Bipyridine-Based Covalent Organic Frameworks for Specific Photocatalytic Fuel Production

“…Utilizing solar energy, photocatalytic H 2 O splitting, and CO 2 reduction to produce energy-rich compounds is anticipated to offer a solution to the issues of fossil fuel shortages and global warming. − Due to their well-defined structure, definite catalytic mechanisms, and high product selectivity, molecular catalysts, especially noble-metal complexes, are widely used in the fields of H 2 evolution reaction (HER), − water oxidation, − and CO 2 reduction reaction (CO 2 RR). − However, the practical application of these noble-metal catalysts has been impeded by their limited reserves and high prices. The heterogenization of these homogeneous molecular catalysts is regarded as an effective approach to enhance their recycling efficiency, thereby reducing usage costs. − …”

A Comprehensive Review on the Boosted Effects of Anion Vacancies in Photocatalytic Solar Water Splitting: Focus on g-C3N4 with Carbon and Nitrogen Vacancies

“…Especially notable are the unique merits of induced nitrogen vacancies (NVs) in visible-light harvesting. 58,59 NVs form the defective mid-gap states (arising from the extra electron accumulated at C-atoms near the vacancy sites of g-C 3 N 4 ) just below the conduction band minimum (CBM). Carbon vacancies (CVs) shift the CBM position to tune the E g of g-C 3 N 4 , improving its redox ability.…”

“…The C- and/or N-deficient g-C 3 N 4 (C/N vacancies) makes a more efficient photocatalyst than bulk g-C 3 N 4 on account of the well-regulated band structure thus extending the light-harvesting range. Especially notable are the unique merits of induced nitrogen vacancies (NVs) in visible-light harvesting. , NVs form the defective mid-gap states (arising from the extra electron accumulated at C-atoms near the vacancy sites of g-C 3 N 4 ) just below the conduction band minimum (CBM). Carbon vacancies (CVs) shift the CBM position to tune the E g of g-C 3 N 4 , improving its redox ability.…”

Sensitization of TiO2/g-C3N4 Heterostructures via Pd–Au Cocatalysts: A Rational Design of Water Splitting System for Green Fuel Production

“…TiO 2 solely was stimulated within the UV spectrum owing to its elevated energy bandwidth (3.0 eV), and it is noteworthy that the UV region accounts for only 4% of sunlight. After TiO 2 , the attention toward graphitic carbon nitride (g-C 3 N 4 ) has been increased due to its favorable band gap ( E g = 2.67 eV), appropriate E g position, cost effectiveness, efficient conductivity, high photocatalytic efficacy, high thermal stability (∼600 °C), dielectric strength, and chemical stability . However, its solar conversion efficiency is limited due to fast charge recombination and low electron mobility.…”