Suppressive Strong Metal‐Support Interactions on Ruthenium/TiO<sub>2</sub> Promote Light‐Driven Photothermal CO<sub>2</sub> Reduction with Methane

Defect-rich Pd/TiO 2 catalysts are intensively adopted in heterogeneous hydrogenation reactions; however, the complexity of the defect structure makes it difficult to precisely identify which Pd-defect combination dominates the catalytic activity. Herein, defective TiO 2 nanoflakes with tunable ratios of Vo to Ti 3+ defects were synthesized and used to construct Pd−Vo and Pd−Ti 3+ active sites after loading Pd to investigate the role of defects in regulating the structural and catalytic properties of defective Pd/TiO 2 catalysts. Combining the experimental results and theoretical calculations, we reveal that both Vo and Ti 3+ defects act as the electron donors for Pd and induce the strong metal−support interaction. When compared to the Vo defect, the Ti 3+ defect behaves more significantly and donates more electrons, causing the Pd species on the catalysts to be better dispersed and more rich in electrons. These unique features endow the Pd−Ti 3+ active centers with enhanced adsorption−activation ability toward C�C and H 2 as well as reduced energy barrier of the rate-limiting step, thus improving the intrinsic activity. The Pd−Ti 3+ site manifests a high turnover frequency of 348 h −1 and hydrogenation degree of 97% for hydrogenation of C�C in styrene−butadiene−styrene, which significantly outperforms the Pd−Vo site (254 h −1 and 78%) and Pd nanoparticle (217 h −1 and 53%). This work provides deep insight into the role of defects in regulating the properties of metal active sites, which can be used to guide the development of high-performance Pd/TiO 2 catalysts for versatile applications.

Section: Resultsmentioning

confidence: 96%

Section: Geometric and Electronic Structures Of Pd/tio 2 Catalystsmentioning

confidence: 98%

Construction of Highly Active Pd–Ti³⁺ Sites in Defective Pd/TiO₂ Catalysts for Efficient Hydrogenation of Styrene–Butadiene–Styrene

Wang,

Ge,

Yang

et al. 2024

“…First, between 1200 and 1500 cm –1 , some additional peaks were observed which was not previously observed in Ag 0.5% /TiO 2 . These peaks are bicarbonate (HCO 3 – ) at 1310 cm –1 , bidentate carbonate (b-CO 3 –2 ) at 1470 cm –1 , and monodentate carbonate (m-CO 3 –2 ) at 1505 cm –1 . The formation of these groups depends on the ability of H 2 O to adsorb by the photocatalysts.…”

Section: Resultsmentioning

confidence: 99%

Particle Size-Dependent Charge Transfer Dynamics for Boosting CO₂ Photoreduction over Ag/TiO₂ Heterojunction

Liu,

Zhou,

Wen

et al. 2024

Photocatalytic CO2 reduction (PCO2R) represents a critical pathway in renewable energy generation. Silver nanoparticles (Ag NPs) of varying sizes were deposited on TiO2 surfaces, exhibiting size-dependent catalytic activities and selectivities due to distinct charge transfer dynamics. The integration of the particle size and Ag/TiO2 Schottky junction density supplied ample active sites for CO2 reduction. Modifying the size of the Ag NPs significantly enhanced the photocatalytic performance of the Ag/TiO2 heterojunction. Notably, Ag0.5%/TiO2 showed a CO generation rate of 86.8 μmol g–1 h–1, which was 1.79 times higher than that of anatase. More importantly, Ag3.0%/TiO2 resulted in the highest selectivity of CH4 (28.1%). The particle size of Ag NPs influenced the ratio of thermal electron transfer during photoexcitation and the intermediate product pathways in the CO2 reduction process. This research provides insights and experimental foundations for particle size regulation in designing heterojunction catalysts for PCO2R.

“…The classical strong metal–support interaction (SMSI) refers to the migration of the partially reduced support to the surface of metal nanoparticles (NPs), resulting in the formation of an encapsulation overlayer. − The SMSI phenomenon has been commonly observed between platinum group metal NPs (i.e., Ir, Ru, Rh, Au, and Pt) and a reducible support (i.e., TiO 2 , Nb 2 O 5 , CeO 2 , and MoO 3 ) via thermal pretreatment under high temperature (≥500 °C) and a specific gas atmosphere (i.e., H 2 , O 2 ). ,− As for most supported metal catalysts, the exposed metal surface sites critically control the catalytic behavior, while the formed encapsulation overlayer around metal NPs would greatly reduce the accessible metal surface sites and affect the chemisorption and activation of small molecules, such as CO, CO 2 , H 2 and even reaction intermediates. − The electronic structure of metal catalysts will also be changed due to the formation of additional metal oxide interfacial sites, and the confined effect exerted by the surface encapsulation could also effectively hinder the sintering of metal NPs under high temperature reaction conditions, thus largely influencing the catalytic activity and selectivity of the hydrogenation process. ,,, …”

Section: Introdutionmentioning

confidence: 99%

Overturning CO₂ Hydrogenation Selectivity via Strong Metal–Support Interaction

Zhang,

Lin,

Wei

et al. 2024

Strong metal−support interaction (SMSI) is commonly observed for platinum-group metals on reducible oxide supports upon a high-temperature reduction (≥500 °C). Herein, we show that the SMSI state can be constructed over a Ru/anatase-TiO 2 catalyst using the CO 2 hydrogenation reaction gas at a low temperature of ∼210 °C, which could overturn the CO 2 hydrogenation selectivity from 100% CH 4 to >99% CO. It is revealed that the exposed metallic Ru nanoparticles promote CH 4 formation via formate intermediates at temperatures <200 °C. Elevating the temperature under a H 2 -containing atmosphere causes the evolution of active TiO x suboxide to form an encapsulated structure of Ru@TiO x , which changes the surface intermediate from formate to carboxy species during CO 2 hydrogenation, thus leading to exclusive CO formation with long-term catalytic stability. The O 2 -containing gas treatment of encapsulated Ru@TiO x could achieve the cyclic switch of product selectivity between CO and CH 4 . This work provides an effective strategy to modulate the SMSI state at a very low temperature.