Morphological effects of nanoparticles are crucial in many solid-catalyzed chemical transformations. We herein prepared two manganese-ceria solid solutions, well-defined MnCeO_x nanorods and MnCeO_x-nanocubes, exposing preferentially (111) and (100) facets of ceria, respectively. The incorporation of Mn dopant into ceria lattice strongly enhanced the catalytic performance in the NO reduction with CO. MnCeO_x (111) catalyst outperformed MnCeO_x (100) counterpart due to its higher population density of oxygen vacancy defects. In-situ infrared spectroscopy investigations indicated that the reaction pathway over MnCeO_x and pristine CeO₂ is similar and that besides the direct pathway, an indirect pathway via adsorbed hyponitrite as an intermediate cannot be ruled out. X-ray photoelectron and Raman spectroscopies as well as first-principles density functional theory (DFT) calculations indicate that the enhanced catalytic performance of MnCeO_x can be traced back to its “Mn—O_L(VÖ)—Mn—O_L(VÖ)—Ce” connectivities. The Mn dopant strongly facilitates the formation of surface oxygen vacancies (VÖ) by liberating surface lattice oxygen (O_L) via CO* + O_L → CO₂* + VÖ and promotes the reduction of NO, according to NO* + VÖ → N* + O_L and 2N* → N₂. The Mn dopant impact on both the adsorption of CO and activation of O_L reveals that a balance between these two effects is critical for facilitating all reaction steps.

Methyl formate is widely employed as one of the important organic intermediates in C1 chemistry and as an environmentally benign chemical in the emerging area of “green chemistry”. We here study the catalytic effectiveness of CuO/TiO₂-nanotube nanocomposites for the direct synthesis of methyl formate via methanol photo-oxidation in this paper. The CuO/TiO₂-nanotube nanocomposites with 7% CuO weight loading give a promising photocatalytic performance (over 93.3% methanol conversion and 89.4% methyl formate selectivity) at 25 °C under 365 nm UV irradiation. The turnover frequency and the apparent quantum efficiency reach up to 22.9 mol_methanol g_cat^–1 h^–1 and 57.6% over 7% CuO/TiO₂-nanotube, respectively, which is mainly because of the effective minimization of the recombination of photogenerated electrons and holes by the surface ultrasmall-sized CuO particles. Furthermore, these CuO/TiO₂-nanotube nanocomposites exhibit excellent durability and robust nature during the catalytic processes of the methanol photo-oxidation to methyl formate. The experimental results demonstrate the promise of the robust CuO/TiO₂ nanocomposites for efficient and green production of methyl formate, which may offer guidelines for the design of efficient catalysts for selective alcohol conversion to other valuable chemicals.

Advanced semiconductor photocatalysts have significant potential for efficient alcohol photooxidation. In this study, a novel 2D/2D g-C₃N₄/SnS (CNS) S-scheme heterojunction was fabricated via a one-step hydrothermal stripping and assembly method, in which SnS nanosheets were in situ anchored on exfoliated g-C₃N₄ nanosheets. The as-prepared CNS composites exhibit superior photocatalytic performance in the photooxidation of benzyl alcohol (BA) to benzaldehyde. This is because constructing the 2D/2D heterojunction interface efficiently provided numerous surface Sn vacancies, enhancing light absorption, and encouraging charge separation and transfer. CNS-10 achieved the best photocatalytic activity with a promising formation rate of 1.63 mmol_{reacted BA} g_catal. ⁻¹ h⁻¹, which is 4-fold more significant than that of pristine g-C₃N₄. Femtosecond time-resolved transient absorption spectroscopy (fs-TAS) reveals that the exceptional performance could be attributed to the effective synergistic promotion of shallow electron trapping in g-C₃N₄ and inhibition of the recombination of photogenerated electrons and holes. Furthermore, the main active species and possible reaction mechanisms during the photocatalytic process were also examined. Overall, this study can offer insights into the rational construction of 2D/2D S-scheme photocatalysts.