Tailoring of Visible to Near-Infrared Active 2D MXene with Defect-Enriched Titania-Based Heterojunction Photocatalyst for Green H₂ Generation

Abstract

A wide solar light absorption window and its utilization, long-term stability, and improved interfacial charge transfer are the keys to scalable and superior solar photocatalytic performance. Based on this objective, a noble metal-free composite photocatalyst is developed with conducting MXene (Ti 3 C 2 ) and semiconducting cauliflower-shaped CdS and porous Cu 2 O. XPS, HRTEM, and ESR analyses of TiO y @Ti 3 C 2 confirm the formation of enough defect-enriched TiO y (where y is < 2) on the surface of Ti 3 C 2 during hydrothermal treatment, thus creating a third semiconducting site with enough oxygen vacancy. The final material, TiO y @Ti 3 C 2 /CdS/Cu 2 O, shows a broad absorption window from 300 to 2000 nm, covering the visible to near-infrared (NIR) range of the solar spectrum. Photocatalytic H 2 generation activity is found to be 12.23 and 16.26 mmol g −1 h −1 in the binary (TiO y @Ti 3 C 2 /CdS) and tertiary composite (TiO y @Ti 3 C 2 /CdS/Cu 2 O), respectively, with good repeatability under visible−NIR light using lactic acid as the hole scavenger. A clear increase of efficiency by 1.53 mmol g −1 h −1 in the tertiary composite due to NIR light absorption supports the intrinsic upconversion of electrons, which will open a new prospective of solar light utilization. Decreased charge-transfer resistance from the EIS plot and a decrease in PL intensity established the improved interfacial charge separation in the tertiary composite. Compared to pure CdS, H 2 generation efficiency is 29.6 times higher on the noble metal-free tertiary composite with an apparent quantum efficiency of 12.34%. Synergistic effect of defect-enriched TiO y formation, creation of proper dual p−n junction on a Ti 3 C 2 sheet as supported by the Mott−Schottky plot, significant NIR light absorption, increased electron mobility, and charge transfer on the conductive Ti 3 C 2 layer facilitate the drastically increased hydrogen evolution rate even after several cycles of repetition. Expectantly, the 2D MXene-based heterostructure with defect-enriched dual p−n junctions of desired interface engineering will facilitate scalable photocatalytic water splitting over a broad range of the solar spectrum.

MXene-Derived Oxide Nanoheterostructures for Photocatalytic Sulfamethoxazole Degradation

“…MXenes with the M n +1 X n T x formula (M: early transition metal, X: C and/or N, T x : functional groups, n = 1–4) are two-dimensional (2D) multilayered materials that recently emerged as cocatalysts for photocatalytic applications due to their unique structural and electronic properties. , As photocatalysts, the formed MXene-derived transition metal oxides (MO x ) can be highly efficient nanomaterials for photocatalytic applications. , MXene-derived MO x are obtained by partial or complete oxidation of MXene (Ti 3 C 2 T x and Ti 2 CT x ) depending on oxidation conditions, and they exhibit superior properties compared to MO x /MXene composites. , Recent advancements in MXene-based photocatalysts highlight their growing significance in environmental and energy challenges, and ongoing research aims to overcome the current limitations and scale up their production for practical applications. − Reported studies pointed out that oxygen-containing functional groups, especially, facilitate the formation of MO x phases . It has been reported that TiO 2 /amorphous carbon sheets can be derived by using flash-heating multilayered Ti 3 C 2 T x in air .…”

“… 18 , 19 As photocatalysts, the formed MXene-derived transition metal oxides (MO x ) can be highly efficient nanomaterials for photocatalytic applications. 20 , 21 MXene-derived MO x are obtained by partial or complete oxidation of MXene (Ti 3 C 2 T x and Ti 2 CT x ) depending on oxidation conditions, and they exhibit superior properties compared to MO x /MXene composites. 22 , 23 Recent advancements in MXene-based photocatalysts highlight their growing significance in environmental and energy challenges, and ongoing research aims to overcome the current limitations and scale up their production for practical applications.…”

Heterostructured Photocatalysts for Water Splitting and the Interfacial Charge Transfer

“…Hydrogen generation through photocatalytic water splitting is an environmentally friendly strategy. It offers potential solutions to both the energy crisis and environmental challenges. − Photocatalysts have an important effect on light absorption efficiency and photocatalytic activity. A typical photocatalytic process involves four consecutive steps .…”