Revealing the Synergistic Effects of Rh and Substituted La₂B₂O₇ (B = Zr or Ti) for Preserving the Reactivity of Catalyst in Dry Reforming of Methane

Abstract

Rh substituted-La 2 B 2 O 7 (B = Zr or Ti) composite oxides were synthesized and applied in the dry reforming of methane (DRM) reaction. The characterizations of XRD, Raman, UV−vis diffuse reflectance, HRTEM, HAADF-STEM, in situ DRIFTS, XAFS XPS, TPR and the tests of DRM reaction have shown that the degree of substitution and the catalytic performance depend on the composition of La 2 B 2 O 7 (B = Zr or Ti). It is found that almost all Rh species substituted Zr over the compact Rh-LZO while a part of Rh substituted Ti, and the rest existed in the form of Rh 2 O 3 on the surface over the loose Rh-LTO. CH 4 was prone to dissociate on Rh−La 2 Zr 2 O 7 but hard to continue owing to the quickly depositing of intermediate carbon, which would not be resolved unless enough active O* was furnished. On the other hand, titanium-doped La 2 Ti 2 O 7 conferred unique structural and charge effects to supported Rh through the metal−support interface, leading to the coexistence of Rh 0 and Rh δ+ which performed synergistically during DRM at 800 °C. We proposed that CH 4 would be activated on Rh sites continuously if generated carbon could be promptly oxidized by active O* species that originated from CO 2 dissociation. The coexistence of Rh 0 and Rh δ+ in Rh−La 2 Ti 2 O 7 facilitated the electron transfer and thus accelerated the mobility of active oxygen species, which could be proved by the variations of binding energy in Ti, O, and Rh.

A Generalized Surface Chalcogenation Strategy for Boosting the Electrochemical N2 Fixation of Metal Nanocrystals

“…Meanwhile, the two weak shoulder peaks at 308.3 and 313.1 eV belong to Rh 3+ 3d 5/2 and Rh 3+ 3d 3/2 , respectively. [ 37 ] However, a slight shift of the Rh 0 3d 5/2 peak toward higher value (307.6 and 312.4 eV) is observed for the Rh‐Se NCs/C compared with Rh NCs/C, indicating the electron transfer from Rh to Se. The asymmetry and tailing of Rh 3d XPS on Rh‐Se NCs/C become more apparent than on that of Rh NCs/C, suggesting additional Rh 3+ species formed after surface selenation of Rh NCs/C.…”

“…Meanwhile, the two weak shoulder peaks at 308.3 and 313.1 eV belong to Rh 3+ 3d 5/2 and Rh 3+ 3d 3/2 , respectively. [37] However, a slight shift of the Rh 0 3d 5/2 peak toward higher value (307. regard to Fermi level) further tunes the binding strength of NRR intermediates, which eventually modulates the catalytic activity. [38] As shown in Figure 4b, the upshift of the d-band center of gravity after introducing Se (Rh-Se NCs/C) was observed, compared with Rh NCs/C, thereby likely strengthening the adsorption of N 2 intermediate.…”

Symmetrical Exsolution of Rh Nanoparticles in Solid Oxide Cells for Efficient Syngas Production from Greenhouse Gases

“…Rh is one of the most active catalysts for methane [40][41][42][43][44][45][46][47][48][49] and carbon dioxide activation [48][49][50][51][52][53][54] . We exemplify how the introduction of CH4 at the anode decreases or even reverses the electrical power demands of the conventional co-electrolysis by simultaneously producing syngas with an up to 100% selectivity.…”

“…S8b), RED800 and RED900 samples display almost identical activities which are slightly higher than RED600 at low currents, hence revealing an interaction between the embedded Rh particles and the perovskite support. It has been proposed that the catalytic activity of Rh is well connected to its oxidation state, and specifically the closer to metallic state, the higher the number of active sites for methane dissociation [40][41][42][43][44][45][46][47] . Particles with size close or below 2 nm, as in the RED600 sample, are prone to remain in the oxidized (Rh 3+ and Rh 4+ ), less active state due to the fast exchange of oxygen species with the support, whereas as the particles size increases up to 4 nm, Rh can maintain the desirable reduced state 55 .…”

Progress in the catalytic conversion of light alkanes withcarbon dioxide

“…高温可以有效抑制CO歧化反应(Bou- [11] . 根据活性金属的种类, 可以 将甲烷干重整催化剂分为贵金属催化剂和非贵金属催 化剂两类: 贵金属催化剂以Ru [12,13] 、Rh [14,15] 、Pt…”