A protozeolite‑like seed‑assisted, urea‑directed, template‑free strategy was developed for the synthesis of nanosheet‑like ZSM‑5 zeolite with a short b‑axis thickness under low gel SiO2/Al2O3 ratio conditions. The synergistic use of protozeolite-like seeds and urea enabled effective control of ZSM-5 crystal morphology. Under optimized conditions (urea/SiO2 = 0.192, gel SiO2/Al2O3 = 45, Na2O/SiO2 = 0.056), the protozeolite‑like seeds directed the crystallization of nanosheet‑like ZSM‑5 with an average b‑axis thickness of 160 ± 5 nm, a relative crystallinity of approximately 90%, and a SiO2/Al2O3 ratio of 46.38. Ni catalysts supported on commercial ZSM-5, conventionally seed-synthesized ZSM-5, and protozeolite-like-seed-assisted nanosheet-like ZSM-5 were prepared to elucidate the influence of zeolite morphology on guaiacol hydrodeoxygenation (HDO). Compared with the commercial and conventionally seed-synthesized counterparts, the short-b-axis ZSM-5 support promoted the formation of smaller and more uniformly dispersed Ni particles. This improved Ni dispersion, together with the reduced intracrystalline diffusion length along the b-axis, enhanced the accessibility of guaiacol and reaction intermediates to the metal and acid sites. Consequently, Ni supported on the protozeolite-like-seed-assisted ZSM-5 exhibited the highest cyclohexane yield during guaiacol HDO. Reaction-pathway analysis further suggested that 1-methyl-1,2-cyclohexanediol may serve as an important intermediate in a non-conventional route toward cyclohexane formation. This work presents a green and template-free route for the synthesis of short-b-axis ZSM-5 at a low SiO2/Al2O3 ratio and highlights the important role of zeolite morphology in regulating Ni dispersion, molecular accessibility, and hydrodeoxygenation performance.
Zeolite-supported noble-metal catalysts can derive selectivity from both pore confinement and the chemical microenvironment that controls metal nucleation, adsorption ensembles, and side-reaction networks. Here, trace-Pd-modified Au catalysts were prepared on two MFI zeolites with identical topology but contrasting surface chemistry: all-silica silicalite-1 (S-1) and Brønsted-acidic ZSM-5. Au alone was essentially inactive for gas-phase butadiene (BD) hydrogenation, whereas trace Pd strongly promoted activity. A nominal 0.05 wt% Pd loading on 1 wt% Au/S-1 gave the best activity-selectivity balance. Electron microscopy revealed Au-rich PdAu particles of ca. 2.3 nm on S-1 but ca. 13.4 nm on ZSM-5. PdAu/S-1 achieved > 90% BD conversion near 373 K with approximately 97–100% total butene selectivity and maintained > 95% conversion for 10 h under a low H2/BD ratio, whereas PdAu/ZSM-5 showed a narrower selectivity window and pronounced deactivation. Temperature-programmed H2-D2 exchange showed that HD-formation activity followed the same catalyst order as BD hydrogenation, identifying hydrogen-activation capability as a key descriptor of low-temperature activity. CO-DRIFTS revealed support-dependent adsorption ensembles, while NH3-TPD, textural analysis, and TGA-MS linked ZSM-5 acidity to oligomerization/aromatization-derived refractory coke. These results reveal substantial differences in PdAu nanostructure, hydrogen activation, adsorption ensembles, and deactivation between the two MFI-supported catalysts.
The oxidative coupling of methane (OCM) offers a promising one-step, autothermal process to produce C2 + hydrocarbons. However, its industrial implementation is hindered by the lack of catalysts delivering high C2+ yields under practical conditions. This study synthesized, characterized, and evaluated a series of lithium carbonate (Li2CO3)-coated lanthanide composite oxides (Ln2O3+x@Li2CO3, Ln = La, Ce, Pr) to merge the advantages of lithium promoters and lanthanide oxides for improved OCM performance. The results indicate that the catalyst composition decisively influences its structure and catalytic properties. The LaPrO3+x@5Li catalyst achieved the highest single-pass C2+ yield of 23.96% at 750 ℃ with excellent stability, retaining about 90% of its initial C2+ yield over 30 h on stream, and its C2+ selectivity remained essentially unchanged when the WHSV was increased fourfold. Comprehensive characterization (XRD, Raman, XPS, O2-TPD and H2-TPR) revealed that the performance correlates strongly with the abundance and mobility of the surface electrophilic oxygen species (O2−, O22−), and with the valence changes of lanthanide ions. Notably, the irreversible reduction of Ce4+ to Ce3+ was identified as a primary cause of deactivation for Ce-containing catalysts. This work provides new insights and a material platform for designing high-performance and stable OCM catalysts.
In2O3-based catalysts are promising for CO2 hydrogenation to methanol but suffer from poor H2 dissociation, sintering, and thermal instability. Herein, we report a high-performance catalyst containing abundant oxygen vacancies stabilized at amorphous/crystalline interfaces within an indium-based ternary oxide (In2O3/ZnO/ZrO2) core encapsulated by ZIF-8 (In2O3/ZnO/ZrO2@ZIF-8), synthesized via a hydrothermal method with in situ ZIF-8 growth. The ternary oxide heterostructure creates abundant amorphous/crystalline interfaces, which not only promote the uniform dispersion of active sites but also induce the formation of spatially extended interfacial oxygen vacancies, enhancing gas adsorption and activation. Specifically, ZnO is suggested to act as a promoter of H2 dissociation, while ZrO2 stabilizes In2O3 against sintering. The ZIF-8 shell further enhances catalytic performance through nanoconfinement, enabling spatial control of active sites and improved mass transfer. Under mild conditions (250 °C, 2 MPa), the optimized In2O3/ZnO/ZrO2@ZIF-8 catalyst achieves a CO2 conversion of 15.6%, a CH3OH selectivity of 86.6%, and a space-time yield (STY) of 0.525 gMeOH·gcat−1·h−1, outperforming conventional In2O3-based catalysts. This superior performance is attributed to the synergistic stabilization of oxygen vacancies at the amorphous/crystalline interfaces and the dual-function confinement of ZIF-8, which collectively enhance both catalytic efficiency and long-term stability. This work provides a novel design strategy for In2O3-derived catalysts by integrating interface engineering with defect chemistry and molecular confinement.
The quest for high-performance multifunctional electrocatalysts that can simultaneously facilitate the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is pivotal for advancing sustainable energy conversion systems. Herein, we rationally designed a series of Bimetallic MBenes with the chemical formula Ni2MB4 (M = Ti, V, Cr, Mn, Fe, Co, Zr, Nb, Mo, Hf, Ta, and W) and conducted a detailed exploration of their potential as multifunctional electrocatalysts using density functional theory. Among all the rationally designed Ni2MB4 catalysts, Ni2TiB4, Ni2VB4, Ni2CrB4, Ni2MnB4, Ni2FeB4, Ni2MoB4, Ni2TaB4, and Ni2WB4 present excellent electrocatalytic performance for both ORR and OER, with corresponding overpotentials of 0.36/0.47, 0.33/0.54, 0.29/0.55, 0.41/0.56, 0.31/0.50, 0.26/0.55, 0.31/0.56 and 0.23/0.54 V, respectively. Remarkably, Ni2CoB4 demonstrates favorable catalytic performance and represents a competitive trifunctional electrocatalyst toward ORR/OER/HER, showing overpotentials of 0.34/0.53/0.24 V. Apart from screening superior electrocatalysts, this work performs electronic structure analyses to elucidate the activity origin. These electronic structure studies further confirm that the adsorption behavior of intermediates plays a crucial role in determining catalytic activity. This study offers novel perspectives on the rational design strategy of advanced MBenes-based multifunctional catalysts.
