Novel Insights on the Metal–Support Interactions of Pd/ZrO₂ Catalysts on CH₄ Oxidation

Abstract

With the environmental harm of unburnt CH4 in natural gas vehicle exhaust, oxidizing CH4 to CO2 over catalysts at low temperatures becomes an exigent issue. Supported Pd catalysts possess higher CH4 activity than other noble metal catalysts. A series of Pd/ZrO2 catalysts were synthesized to research the potential relationship among Pd particle morphology, electron transfer, CH4 oxidation mechanism, and catalytic activity. Characterizations show that the ratio of PdO x facets to edge/corner sites on four catalysts increases in the order of PZ85 ≈ PZ40 < PZ55 < PZ70 because of the difference in content of surface −OH groups, and this order turns out to be the same as that of electron transfer intensity, revealing the degree of metal–support interactions. This kind of metal–support interaction in PZ70 can be helpful to accelerate CH4 combustion via promoting the break of the C–H bond and dissociation of CO3* according to density functional theory studies. T 90 of the PZ70 catalyst with optimum catalytic activity reaches 331 °C.

Creating Atomically Iridium-Doped PdOx Nanoparticles for Efficient and Durable Methane Abatement

“…7,60 This signal gradually diminished as the reaction temperature increased to 450 °C, accompanied by the appearance of adsorbed CO 2 (2355 and 2382 cm −1 ). 25,61 Methane oxidation was enhanced on the PdIrx/S-1 samples, as evidenced by the lower temperatures for CO 2 formation observed on PdIr 0.1 /S-1 (400 °C) and PdIr 0.25 /S-1 (350 °C) (Figure 4f and Figure S22). This result was consistent with the CH 4 -TPR experiment as well as their catalytic performance in methane combustion.…”

“…In situ DRIFTS experiments were conducted to investigate the reactive intermediates of methane oxidation on these PdIr x /S-1 catalysts. During steady-state methane oxidation on Pd/S-1 (Figure S21), the C–H stretching signal (3016 cm –1 ) of CH 4 species was observed at 300 °C. , This signal gradually diminished as the reaction temperature increased to 450 °C, accompanied by the appearance of adsorbed CO 2 (2355 and 2382 cm –1 ). , Methane oxidation was enhanced on the PdIr x /S-1 samples, as evidenced by the lower temperatures for CO 2 formation observed on PdIr 0.1 /S-1 (400 °C) and PdIr 0.25 /S-1 (350 °C) (Figure f and Figure S22). This result was consistent with the CH 4 -TPR experiment as well as their catalytic performance in methane combustion.…”

TiO2 Coating on SiO2 Nanosphere Supported Pd Catalyst for the H2–SCR of NOx in the Presence of Oxygen

“…Figure (a) shows the Pd 3d XPS spectra of the two catalysts. For 0.5Pd/TiO 2 catalyst, there are two XPS peaks at about 337.1 and 342.4 eV, which can be assigned to Pd 2+ . , Compared with 0.5Pd/TiO 2 , the peak position over 0.5Pd/SiO 2 –TiO 2 (C) was shifted to lower binding energy by ∼0.5 eV, which suggests a stronger interaction existed between Pd and SiO 2 –TiO 2 (C). , The XPS speaks for 0.5Pd/SiO 2 –TiO 2 (C) can be divided into three separate peaks at 335.5, 336.6, and 341.8 eV, which are ascribed to Pd 0 and Pd 2+ , respectively . The Pd 0 /(Pd 0 + Pd 2+ ) ratio over 0.5Pd/SiO 2 –TiO 2 (C) was about 6.2%.…”

Bridge-type Mn–O–Mn sites promoting catalytic methane oxidation and carbonate desorption over Mn-based oxides

“…6 At present, noble metal catalysts show good catalytic performance for CH 4 oxidation. 7,8 Park et al 9 synthesized a Pd/Pt catalyst for CH 4 oxidation. The results showed that the interaction of Pd and Pt easily yields active PdO-Pt counter-sites to promote CH 4 oxidation.…”

“…Gas-phase CO 2 was adsorbed on terminal-type oxygen MnO to form a surface monodentate carbonate (v as (CO 5 and 6). Mn-□-Mn might be produced because the O 2 decomposition rate to Mn-O-Mn following eqn (8) was lower than the Mn-O-Mn consumption rate (eqn ( 4)). The Mn-O-Mn regeneration experiments in an O 2 /Ar atmosphere (Table S1 †) were conducted.…”