Ti³⁺ Defective TiO₂/CdS Z-Scheme Photocatalyst for Enhancing Photocatalytic CO₂ Reduction to C1–C3 Products

Abstract

Photocatalytic CO 2 reduction is a promising route to simultaneously address two critical issues related to the energy and environment. Herein, a direct Z-scheme photocatalytic system, Ti 3+ defective TiO 2 /CdS nanoflowers, was fabricated to enhance the production of C1−C3 products from CO 2 reduction. First, nanoflowerlike TiO 2 (NF-TiO 2 ) is prepared using a TiB 2 precursor to build in Ti 3+ defects. Then, the NF-TiO 2 /CdS heterojunctions are constructed via the sulfurization of TiO 2 /Cd-MOF. Importantly, the optimal heterojunction photocatalyst NF-TiO 2 /CdS 0.6 exhibits a highly promoted CO 2 reduction activity not only for CO and CH 4 but also for C2−C3 hydrocarbons. The cumulative yields of CO and CH 4 are 1007.0 μmol/g and 83.5 μmol/g (2.5 h), respectively, and a yield of 55.3 μmol/g (2.5 h) of C2−C3 hydrocarbons is obtained. This enhanced yield of C1−C3 products is attributed to the synergistic effects of abundant Ti 3+ defects that increase adsorption and activation of CO 2 , the large surface area that provides sufficient active sites, and a direct Z-scheme heterojunction with a good intimate contact interface that effectively separates charge carriers and accumulates electrons with strong reducibility. Moreover, the photoluminescence analysis of hydroxyl radicals was conducted to provide evidence for the direct Zscheme mechanism. This work provides a facile method for the construction of a TiO 2 -based direct Z-scheme photocatalytic system for improving photocatalytic performance toward CO 2 reduction.

Anchoring 0D Cd0.5Zn0.5S nanoparticles on a 3D porous N-doped Ti3C2Tx MXene matrix for efficient photocatalytic hydrogen evolution

“…52 Moreover, EPR measurement were further used to detect unsaturated defects. 53 As shown in Fig. 3f, both TCT MXene and N-TCT MXene exhibit obvious signals at g = 2.02, indicating the presence of the surface Ti 3+ species defects, which was consistent with the XPS analysis results.…”

Electro- and Photoinduced Interfacial Charge Transfers in Nanocrystalline Mesoporous TiO2 and TiO2/Iron Porphyrin Sensitized Films under CO2 Reduction Catalysis

“…Previously, it was described that Ti 3+ sites could enhance the chemisorption of CO 2 and entail its activation to undergo C–O bond cleavage . Also, the photogenerated electrons accumulated in the TiO 2 intraband states were claimed to facilitate multielectron-transfer processes, generating C 2 and C 3 hydrocarbons . Nevertheless, we have not observed the presence of C 2 and C 3 products in the present study.…”

2D/2D Carbon Nitride/Zn-Doped Bismuth Vanadium Oxide S-Scheme Heterojunction for Enhancing Photocatalytic CO2 Reduction into Methanol

“…In addition to being a considerable organic precursor for the synthesis of various downstream chemicals, CH 3 OH can also be directly employed as a clean fuel and liquid hydrogen carrier. , However, the reduction process of CO 2 to CH 3 OH with a long reaction pathway involves consecutive multielectron/proton transfer and coupling steps, leading to slow surface reaction kinetics, and that severe electron/hole recombination may further limit the photocatalytic performance. Meanwhile, the competitive reaction in the catalytic process may also generate undesired byproducts, resulting in poor product selectivity. , Consequently, from the perspectives of both thermodynamics and kinetics, it is exceedingly challenging to realize the efficient photocatalytic conversion of CO 2 to CH 3 OH.…”

“…Meanwhile, the competitive reaction in the catalytic process may also generate undesired byproducts, resulting in poor product selectivity. 12,13 Consequently, from the perspectives of both thermodynamics and kinetics, it is exceedingly challenging to realize the efficient photocatalytic conversion of CO 2 to CH 3 OH.…”