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Hydroformylation reactions promoted by Rh single-atom catalysts typically exhibit a negative reaction order for CO and a positive reaction order for H 2 and alkenes. To enhance the catalytic activity, efforts have been concentrated on reducing the CO adsorption strength and/or enhancing the hydrogenation capacity at Rh sites. This report introduces an optimized Rh single-atom catalyst, utilizing positively charged Mn species to weaken the CO adsorption strength. Our strategy involves placing MnOx clusters in the proximity to the Rh single atom. This arrangement allows the reduction of Rh3+ to produce electronically deficient Rhδ+ species (1 < δ < 2), rather than the usual formation of the lower valence state Rh+ species. The weakened CO adsorption strength on the more positively charged Rhδ+ results in reduced CO coverage on the Rh active site, and enhanced adsorption of propylene. Our mechanistic study reveals that H 2 and CO adsorption on Rh catalyzes the reduction of adjacent Mn(IV) species, inducing the formation of a Rh-MnOx paired active site. The neighboring MnOx clusters hinder the extensive reduction of Rh3+ to Rh+. This study presents MnOx as an inorganic ligand in Rh-MnOx pair site modifies the electronic properties of Rh sites to modulate the hydroformylation activity of Rh single-atom catalysts. [Display omitted] • H 2 and CO on Rh catalyzes the reduction of adjacent Mn(IV) to form Rh-MnOx pair site. • The neighboring MnOx hinder the reduction of Rh3+ to Rh+, forming Rhδ+ (1 < δ < 2). • Rhδ+ shows weakened CO adsorption strength than Rh+ species • Weakened CO adsorption strength on Rhδ+ benefits high hydroformylation activity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ga geometrically and electronically modify Ni in Ni-Ga alloy and IMC. • Direct deoxygenation (DDO) was more preferential on Ni-Ga alloy and IMC than Ni. • Benzene hydrogenation, C C cleavage and methanation was suppressed on alloy and IMC. • H 2 was generated from anisole via methanol decomposition on Ni-Ga alloy and IMC. • There was a synergetic effect between Ni and Ga on alloy and IMC for HDO. Abstract Herein, Ni/SiO 2 and bimetallic Ni x Ga/SiO 2 (Ni/Ga atomic ratio x = 6 and 3) catalysts were prepared by the impregnation method followed by reduction at 550 °C and tested in the vapor hydrodeoxygenation of anisole at 0.1 MPa and 300 °C. Ni-Ga alloy and Ni 3 Ga intermetallic compound (IMC) formed in Ni 6 Ga/SiO 2 and Ni 3 Ga/SiO 2 , respectively, where the Ga atoms break contiguous Ni ones reducing the ensembles of Ni atoms and the H 2 uptakes. Also, a charge transfer from Ga to Ni increased the electron density of Ni, and hydrogen spill-over occurred on Ni x Ga/SiO 2. In contrast to Ni/SiO 2 , Ni x Ga/SiO 2 improved not only the hydrodeoxygenation activity but also the selectivity to benzene. At the similar anisole conversion (˜31%), the selectivity to benzene was 75.2%, 83.0% and 92.6% on Ni/SiO 2 , Ni 6 Ga/SiO 2 and Ni 3 Ga/SiO 2 , respectively. Reactivity evaluation, anisole-TPD and TPSR results show that the direct C Ar OCH 3 bond cleavage (C Ar represents the carbon in benzene ring) to benzene was more preferential on Ni x Ga/SiO 2 than on Ni/SiO 2. Isotope tracing experiment indicates that the spilt-over hydrogen at the interface between the Ni 3 Ga particles and support participated in the reaction. We suggest that the synergetic effect between Ni and Ga facilitated the direct C Ar O bond cleavage. Moreover, Ni x Ga/SiO 2 were less active for benzene hydrogenation and C C bond hydrogenolysis than Ni/SiO 2 , contributing to higher selectivity to benzene. Significantly, methanol, derived from the direct the C Ar OCH 3 bond cleavage, dominatingly decomposed to CO and H 2 and methanation scarcely occurred on Ni x Ga/SiO 2 , however, it was mainly converted to methane on Ni/SiO 2. Low activities for benzene hydrogenation, C C bond hydrogenolysis and methanation on Ni x Ga/SiO 2 (especially Ni 3 Ga/SiO 2) are attributed to the geometric and electronic effects of Ga in alloy and IMC. The finding is significant in rationally designing the catalyst with high benzene yield and low H 2 consumption. [ABSTRACT FROM AUTHOR]

Abstract: Titania (TiO2) was immobilized onto hydroxylated glass beads (HGB) via the thermal bonding and sol–gel coating methods. The photocatalytic activity and adherence stability of the prepared supported photocatalysts were studied in a fluidized bed photoreactor. P25 thermally bonded HGB was found to be more active than sol–gel coated HGB prepared with the same immobilization conditions, while both of them exhibited poor adherence stability, i.e., large amounts of immobilized TiO2 detached from HGB during the degradation. The adherence stability was improved with limited extents by increasing the calcination temperature or reducing the coverage of TiO2 on HGB, but either of these approaches resulted in lower activity. The poor adherence stability was ascribed to the fluid shear force and particle friction in fluidized bed, as well as the insufficient bonding between TiO2 and HGB in terms of the bonding mechanism. Hydroxylated quartz sands (HQS) and silica gel beads (SGB) were further studied and used as supports. Results have shown that the adherence stability was significantly improved with SGB but only slightly improved with HQS. Characterizations results showed that a coarser surface and more surface Si–OH groups could improve the adherence stability of supported TiO2 photocatalysts. [Copyright &y& Elsevier]

In this work, metal oxides with different phase structures (stannic oxide, zirconia and tin-zirconium binary oxide) were designed to construct palladium-based catalysts. The factors affecting methane combustion over catalysts were revealed by exploring the reasons for the enhancement and depression of catalytic performance under various reaction conditions. The formation of Sn x Zr 1−x O 2 solid solutions not only generated abundant oxygen vacancies to improve the reducibility of PdO and the redox of Pd↔PdO, but also induced the formation of active PdO x , conjointly leading to the excellent catalytic activity and hydrothermal stability. Under SO 2 -containing atmosphere, the thermodynamically favorable formation of stable Zr(SO 4) 2 caused the significant diminish of oxygen vacancies and active Pd step sites in catalysts. Consequently, the sulfur-resistance and regeneration performance of Zr-containing catalysts were inferior to those of Pd/SnO 2. The above contrast manifested that both oxygen vacancies and active palladium species were responsible for the efficient and stable methane combustion. [Display omitted] • Supports of different phase structures were designed for preparing Pd-based catalysts. • Sn x Zr 1−x O 2 solid solutions gave rise to oxygen vacancies and active PdO x species. • Oxygen vacancies improved the reducibility of PdO and the redox of Pd↔PdO. • Suppressed oxygen vacancies and Pd sites by sulfates led to deactivation of catalysts. • Oxygen vacancies and active Pd sites on catalysts were crucial for methane combustion. [ABSTRACT FROM AUTHOR]

The localized plasmon resonance (LSPR) is recognized as an effective way to convert incident light energy and significantly boost the catalytic reaction. However, a comprehensive understanding of the plasmon-thermo coupling mechanism is still lacking. To address this knowledge gap, we investigate reaction pathway and plasmonic enhancement mechanism of the photo-thermo coupled catalytic reverse water gas shift (RWGS) reactions over Au/γ-Al 2 O 3. The results indicate that both formate and carboxyl pathways contribute to the overall reaction. The m-formate pathway is suggested as the main reaction mechanism at low reaction temperature over small Au NPs. Spectro-kinetics and theoretical calculation analyses indicate that the plasmonic energy preferentially transfers to HCOO* via a combination of hot electron and resonance energy transfer mechanisms. The plasmonic energy facilitates the dehydration of HCOO* to CO, which is the rate-determining step (RDS) of the overall RWGS reaction. [Display omitted] • Plasmon enhances the CO 2 hydrogenation rate by ∼211.8 % over Au/Al 2 O 3. • m-HCOO* is demonstrated as the main reaction intermediate over small-size Au/Al 2 O 3. • br-HCOO* is proven as a reaction intermediate contributing to CO production. • Plasmon preferentially enhances the br-HCOO* pathway via promoting its dehydration. • Both "hot" electrons and resonance energy transfer are the promoting mechanisms. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hydrodeoxygenation of waste cooking oil over a dispersed nano CoMoS catalyst. [•] Study of kinetics over the active phase of catalyst only and without acidity. [•] Hydrodecarbonylation/decarboxylation (HDC) is predominant reaction pathway. [•] Direct hydrodecarbonylation from fatty acid is main path for HDC reaction. [•] Reduction of HDC activity is attributed to gradual loss of sulfur on the catalyst. [ABSTRACT FROM AUTHOR]

SYNOPSIS: Coupling photo- and thermo- catalytic CO 2 hydrogenation is a promising way to convert CO 2 with higher sustainability. Herein, the redox pathway is demonstrated as the main reaction pathway for CO 2 hydrogenation at 200 °C over Au/TiO 2. The plasmonic enhancement mechanism is proven to be the facilitated oxygen vacancy generation. [Display omitted] • Plasmon enhances the CO production rate by ∼ 318 % at 200 °C over Au/TiO 2. • Redox mechanism is proven as the main pathway for CO 2 hydrogenation to CO. • DRIFTS analyses prove the spontaneous dissociation of CO 2 at V O site of Au/TiO 2. • Inverse H/D kinetic isotope effects suggest the V O creation is the RDS. • Plasmon-thermo coupling mechanism is the hot-electrons enhanced V O creation. Using solar energy to promote the thermocatalytic CO 2 conversion is a promising way to reduce the energy consumption and increase the sustainability. Au/TiO 2 is known for its good catalytic activity in both thermo- and photo- catalytic CO 2 conversion, however both the reaction mechanisms in dark and in photo-thermo coupled reaction condition remain unclear. In this work, the operando isotope-labelled spectroscopic and computational analyses are combined to clarify these mechanisms. The redox mechanism that CO 2 direct dissociation at the oxygen vacancy (V O) is found as the main reaction pathway of CO 2 hydrogenation over Au/TiO 2. The plasmonic enhancement mechanism is proven to be the hot electrons facilitated V O generation at interface. The clear understandings of reaction pathway and plasmonic enhancement mechanism are helpful for the future design of photo-thermal CO 2 conversion catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • 20 % selectivity to C 2 H 6 is achieved over Au/TiO 2-x under visible light irradiation. • Positively-charged Au clusters due to plasmonic excitation stabilize adsorbed CO. • The CO 2 photocatalytic reduction mechanism is unravelled with in-situ DRIFTS. • Oxygen vacancies are crucial for photocatalytic CO 2 reduction with H 2 O. CO 2 photocatalytic conversion with H 2 O is an attractive technology to convert green-house gas into value-added chemicals. However, the main limitation of this process is the low selectivity to products higher than C1. The reaction mechanism, especially C C coupling mechanism, is still ambiguous. In this work, the photocatalytic CO 2 reduction with H 2 O is investigated on oxygen-deficient Au/TiO 2-x driven by UV or visible light under continuous flow condition. Notably, an exceptional high selectivity of 20 % towards C 2 H 6 is achieved over 2.76 wt% Au/TiO 2-x under plasmonic excitation with the essential involvement of oxygen vacancy (V O). The reaction pathway is reasonably proposed based on a series of in-situ characterization results: the in-situ DRIFTS determined key reaction intermediates, electronic property of Au under excitation state and the critical role of V O. The high selectivity towards C 2 H 6 is explained by the slightly positive-charged Au in Au/TiO 2-x under plasmonic excitation and the enhanced *CO stability. [ABSTRACT FROM AUTHOR]

• Co-OMA with catalytic active sites for methane combustion was synthesized. • Pd-Co bimetallic catalysts with different microstructure were synthesized. • The difference in microstructure led to the difference in catalytic performance. • Pd-Co bimetallic catalysts displayed excellent stability. Cobalt-doped ordered mesoporous alumina (Co-OMA-y) with intrinsic activity for methane combustion were synthesized through a sol-gel method. Results indicated that for Co-OMA-y and supported Pd/Co-OMA-y catalysts, the cobalt doping amount affected the surface concentration of Co2+ and active oxygen species, caused different catalytic activity. Pd/Co-OMA-6 presented abundant active oxygen species, which favored for stabilizing PdO phase, inducing its lower activation energy and higher activity. For Pd-Co bimetallic catalysts with same composition (6 wt.% Co, 0.5 wt.% Pd), different introducing methods of cobalt altered the microstructure, hence affecting the synergism of bimetals. For Pd/6CoDEG/OMA, the better reducibility of PdO made the reaction proceed through Mars-van-Krevelen mechanism, cobalt oxides contributed to the reoxidation of palladium species, meanwhile the optimal surface acidity and basicity benefited the methane adsorption, therefore invoking the excellent activity, long-term and hydrothermal stability. The catalytic performance was greatly improved after stability test due to the redistribution of active species. [ABSTRACT FROM AUTHOR]