Metal-support Interaction Research Articles

Rare earth oxide promoted Ru/Al2O3 dual function materials for CO2 capture and methanation: An operando DRIFTS and TGA study

Dual-function materials (DFMs) combine sorbent and catalytic components to perform selective CO2 capture and subsequent hydrogenation. This study explores the performance of rare-earth oxides (REOs) as CO2 adsorption sites on Ru/Al2O3. REOs increase CO2 uptake by upwards of +60 % by enhancing the overall catalyst surface basicity and favoring metal–support interactions. Thermogravimetric analysis during CO2 adsorption-hydrogenation cycles exhibited significant catalytic activity and enhanced stability of Ru-REO/Al2O3 at temperatures as low as 200 °C. This leads to methane production of 50–85 µmol g−1, surpassing recently reported values obtained for alkali and alkali-earth promoted Ru-based materials operated at 250 °C. The highest performing studied DFM, RuNd2O3/Al2O3, achieved 85 % CO2 capture efficiency and steadily produced methane in cyclic operation (+120 % CO2 uptake relative to Ru/Al2O3). Operando DRIFTS revealed that the dominant mechanism for methane formation is the hydrogenation of ruthenium carbonyls, which are stabilized by REOs. Upon CO2 exposure, surface carbonates and bicarbonate species form more abundantly on DFMs than on Ru/Al2O3. This confirms that REOs enhance the adsorption and retention of carbonates, which generate additional promoter-related reaction pathways during low-temperature hydrogenation. These findings are crucial in the advancement of sustainable, wider operation range carbon capture and utilization technologies.

The Contradicting Influences of Silica and Titania Supports on the Properties of Au0 Nanoparticles as Catalysts for Reductions by Borohydride

This study investigates the significant impact of metal–support interactions on catalytic reaction mechanisms at the interface of oxide-supported metal nanoparticles. The distinct and contrasting effects of SiO2 and TiO2 supports on reaction dynamics using NaBD4 were studied and focused on the relative yields of [HD]/[H2] and [D2]/[H2]. The findings show a consistent increase in HD yields with rising [BD4-] concentrations. Notably, the sequence of HD yield enhancement follows the order of TiO2-Au0-NPs < Au0-NPs < SiO2-Au0-NPs. Conversely, the rate of H2 evolution during BH4- hydrolysis exhibits an inverse trend, with TiO2-Au0-NPs outperforming the others, followed by Au0-NPs and SiO2-Au0-NPs, demonstrating the opposing effects exerted by the TiO2 and SiO2 supports on the catalytic processes. Further, the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) confirms the catalytic mechanism, with TiO2-Au0-NPs demonstrating superior activity. The catalytic activity observed aligns with the order of TiO2-Au0-NPs > Au0-NPs > SiO2-Au0-NPs, suggesting that SiO2 donates electrons to Au0-NPs, while TiO2 withdraws them. It is of interest to note that two very different processes, that clearly proceed via different mechanisms, are affected similarly by the supports. This study reveals that the choice of support material influences catalytic activity, impacting overall yield and efficiency. These findings underscore the importance of selecting appropriate support materials for tailored catalytic outcomes.

Selective hydrogenation of acetylene over Pd/β-Mo2C catalyst: Experimental and theoretical studies

Molybdenum carbide is a promising support to tune the metal reactivity, which originates from the interaction between metal and support. In this work, Pd/β-Mo2C was prepared using a deposition-precipitation method for selective hydrogenation of acetylene. The high temperature calcination is employed to modulate the interaction between Pd and β-Mo2C. The Pd/β-Mo2C catalyst calcined at 600 °C exhibits significant promotion in selective hydrogenation, which shows 100 % acetylene conversion and 81.4 % ethylene selectivity at 160 °C. The activity promotion originates from the enhanced electronic metal-support interaction, which induces a shift of Pd 3d to higher binding energy. Besides, the Pd species become atomically dispersed after calcination. The changes in geometric and electronic structure suppress the formation of Pd hydrides, which consequently inhibits the excessive hydrogenation capacity of Pd. The structure variation also affects the adsorption of ethylene. No strong adsorbed ethylene (di-σ bonded ethylene) can be identified, which is conducive to the improvement of ethylene selectivity. Density functional theoretical (DFT) calculations confirm that Pd on β-Mo2C is positively charged. The desorption energy of C2H4* (0.78 eV) is significantly lower than that of further hydrogenation (1.45 eV), which explains the improved ethylene selectivity of the calcinated catalyst. The present study indicates calcination is an effective method to tune the activity of Pd/β-Mo2C for reactions beyond selective hydrogenation of acetylene.

The coexistence of highly dispersed Pt2+ and Pt0 co-catalysts on chemically oxidized g–C3N4 via metal-support interaction: The effect of reduction time on Pt species and hydrogen evolution of Pt/g-C3N4 photocatalysts

Platinum (Pt) cocatalyst greatly enhances the photoactivity of the graphitic carbon nitride (g-C3N4) photocatalyst for photocatalytic H2 evolution where the Pt properties are critical to determine the photocatalytic activity. In this study, highly dispersed Pt was successfully loaded onto chemically oxidized g–C3N4 (OCN) via a hydrogen reduction process over different reduction time. OCN photocatalysts containing highly dispersed Pt2+/Pt0 exhibited outstanding charge separation efficiency and photocatalytic performance. Symmetrical –CO groups on the OCN surface specifically interacted with atomic Pt2+, and the Pt2+ atoms were stably reduced to Pt0 atoms along with the generation of –OH groups over time. The coexistence of Pt0 and Pt2+ promoted superior photocatalytic performance because the photoinduced charge transfer was facilitated by the Pt0 atoms, which was evidenced by the DFT calculation and the EIS, PL, and photocurrent response results. Consequently, after the 24 h reduction, the highly stable and active Pt2+/Pt0 atoms were effectively distributed over OCN, resulting in the highest HER activity at 4091.3 µmol g−1 h−1.

Sustainable and efficient catalytic oxidation of chlorinated volatile organic compounds over Ru-loaded facet-engineered {201}-TiO2 catalyst with tuned defects

Sustainable and efficient catalytic oxidation of chlorinated volatile organic compounds (CVOCs) poses an enduring challenge. This bottleneck arises from the limited catalytic activity of redox reactions and chlorine desorption, causing catalyst deactivation and secondary pollution. Herein, our sound strategy involves Ru-loaded facet-engineered {201}-TiO2 with tuned defects, thereby boosting its reactivity. Comprehensive characterizations and DFT calculation manifested that Ru/{201}-TiO2, with abundant oxygen vacancies, Ti3+ defects, and robust metal-support interaction, enabled flexible electron transfer to activate O2 and the dissociation of H2O, thus facilitating the continuous generation of reactive oxygen species (ROS), such as •O2– and hydroxyl species. These ROS effectively enhance chlorine desorption and chlorobenzene deep oxidation. Ru/{201}-TiO2 exhibited superior reactivity for chlorobenzene degradation, with an apparent activation energy (Ea) of 31.0 KJ/mol and 100 % chlorobenzene conversion in a 1000-min stability test, even with H2O introduction. Ru/{201}-TiO2 produced 2.2–3.1 times fewer small-molecule chlorinated byproducts than Ru/{101}-TiO2, with no polychlorinated benzenes detected.

Constructing ultralow-loading Cu single atoms/Fe2O3 particles on Nb2C MXenes for efficient utilization of atomic H to boost electrochemical debromination

Bromate is a commonly identified carcinogenic and genotoxic disinfection byproduct in water. Electrochemical debromination is an environmentally friendly and effective approach but it often suffers the limited reducing atomic H (H*) ability and high metal catalyst dosage. In this study, a unique composite catalyst comprised of ultra-low loading Cu single atoms (0.016 wt%) and Fe2O3 nanoparticles supported on a Nb2C MXene (denoted as Cu0.2/Fe0.1/Nb2C) was synthesized by one-step high-temperature molten salt method. The Cu0.2/Fe0.1/Nb2C significantly outperformed the Nb2C, Cu0.2/Nb2C and Fe0.1/Nb2C counterparts in the electrochemical debromination with a 94.2 % removal efficiency of bromate. It is revealed that the introducing of Cu single atoms, efficiently promotes the adsorption of H* and inhibition of competitive H2 evolution. The incorporation of Fe2O3 nanoparticles significantly increased the electronic metal-support interaction effect between the metal components and Nb2C, thereby forming a noticeable electronic cloud bridge to facilitate efficient charge transfer. Ultimately, the synergistic interplay between Cu single atoms and Fe2O3 nanoparticles plays a crucial role in achieving the remarkable removal performance of bromate. This work not only presents a significant instance of a synergistic catalyst involving metal single atoms and metal nanoparticles for effective electrochemical debromination but also advances the understanding of the electronic metal-support interaction.

Microwave‐Assisted PtRu Alloying on Defective Tungsten Oxide: A Pathway to Improved Hydroxyl Dynamics for Highly‐Efficient Hydrogen Evolution Reaction

AbstractPlatinum (Pt)‐based compounds are the benchmarked catalysts for hydrogen evolution reaction (HER) but exhibit slow kinetics in alkaline environments. The *OH accumulation on Pt surface can block active sites, affecting proton reduction and water re‐adsorption. Alloying Ruthenium (Ru) with Pt sites can significantly modulate the adsorption and desorption of water dissociation intermediates. Choosing suitable supports and utilizing metal‐support interaction (MSI) is crucial for active site optimization. PtRu alloy anchored on tungsten oxide (WO3) with rich oxygen vacancies (OV) is prepared through an ultrafast microwave‐assisted approach. Benefiting from the coupling effects between alloying and MSI, PtRu/WO3‐OV exhibits exceptionally high HER activity. In 1 m KOH, 1 m KOH + seawater, and 0.5 m H2SO4, it requires ultralow overpotentials of 9, 26, and 6 mV to achieve 10 mA cm−2, respectively. The designed catalyst surpasses commercial Pt/C in mass activity and demonstrates considerable potential for intermittent energy integration. Density functional theory reveals that alloying Ru with Pt sites significantly reduces the energy barrier of dissociating *OH, modulating blockage on the surface and then promoting the overall alkaline HER process. This study offers insights into the rapid synthesis of non‐carbon supported catalysts with Pt site modulation for alkaline hydrogen generation.

Metal‐Support Interaction Boosts Au Catalysts for Hydrogen Evolution‐Coupled Ethanol Electro‐Oxidation Reaction

AbstractElectrochemical hydrogen and acetate cogeneration from ethanol is a promising green hydrogen production technique with low hydrogen production energy consumption and high profitability. However, the poor catalytic stability of the anodic ethanol electro‐oxidation reaction (EOR) retards the device application. We adopted a metal support interaction strategy to reinforce small‐sized Au active sites using cuprous sulfide supports. The Au−Cu2–xS/C showed a superior activity of 1055 mA mgAu−1 at 1.1 V vs. RHE and retained the high activity in the chronopotentiometric test, surpassing the Au/C catalyst. It was demonstrated that the Cu2–xS support facilitated the formation of Au−OH and prevented the gold sites from aggregation, leading to high activity and stability for EOR. Finally, an electrochemical cogeneration electrolyzer assembled with the Au−Cu2–xS/C anodic catalyst continuously ran for over 100 hours, suggesting the device‘s applicability.

Electronic interaction and band alignment between Cu sub-nanometric clusters and ZnIn2S4 nanosheets towards selective photoreduction of CO2 to CO

Engineering the electronic properties of heterogeneous photocatalysts with charge transfer regulated is an effective strategy to boost their CO2 reduction activity. Here, we drew inspiration from the strong metal-support interaction effect, and fabricated ZnIn2S4 supported-Cu sub-nanometric clusters photocatalyst. Within this catalyst, the formed CuS bond would redistribute interfacial charge, resulting in diverse chemical states of Cu atoms and the establishment of Ohmic contact between ZIS and Cu. The built-in electric field of such Ohmic contact benefited the migration of photoexcited electrons from ZIS to Cu. Further mechanistic studies unveiled the crucial role of positively charged Cu atom near the interface in facilitating H2O dissociation, and its adjacent Cu atom at the top-surface adopting a distinct chemical state could activate linear CO2 molecule into a bent configuration. These features substantially lowered energy barriers for CO2 adsorption and subsequent *COOH formation, and Cu-ZIS, accordingly, exhibited a remarkable CO production rate of 60.2 μmol g-1h−1, approximately 20.8-fold enhancement compared to ZIS counterpart.

Enhanced durability of Pd/CeO2-C via metal-support interaction for oxygen reduction reaction.

It is a challenge to improve the long-term durability of Pd-based electrocatalysts for oxygen reduction reaction (ORR) in fuel cells. Herein, Pd/CeO2-C-T (T= 800 °C, 900 °C and 1000 °C) hybrid catalysts with metal-support interaction are prepared from Ce-based metal organic framework precursor. Abundant tiny CeO2nanoclusters are produced to form nanorod structures with uniformly distributed carbon through a calcination process. Meanwhile, both carbon and CeO2nanoclusters have good contact with the following deposited surfactant-free Pd nanoclusters. Benefited from the large specific surface area, good conductivity and structure integrity, Pd/CeO2-C-900 exhibits the best electrocatalytic ORR performance: onset potential of 0.968 V and half-wave potential of 0.857 V, outperforming those obtained on Pd/C counterpart. In addition, the half-wave potential only shifts 7 mV after 6000 cycles of accelerated durability testing, demonstrating robust durability.

Boosting the active sites of Cu/Ce0.8Zr0.2O2 catalysts through tailored precipitation method

A reverse co-precipitation method was employed to increase the surface area of Ce0.8Zr0.2O2, resulting in boosting the active sites of Cu catalysts in the water–gas shift reaction (WGS). Active Cu sites and oxygen vacancy have been systematically controlled through the modification of physical properties and geometric configuration via a reverse co-precipitation of Ce0.8Zr0.2O2 support. The catalytic activity in WGS is primarily dependent on the number of active Cu species and is partially on the oxygen storage capacity. The kinetic results with Cu loadings revealed that the efficiency of active metal utilization was effectively enhanced by a reverse co-precipitation method, compared to the normal precipitation method, owing to the moderate metal–support interactions. The turnover frequency values were independent of Cu dispersion, highlighting the structure-insensitivity of Cu/Ce0.8Zr0.2O2 catalysts. This work suggests the possibility of controlling metal–support interactions through support synthesis methods.

Strong metal‒support interaction modulates catalytic activity of Ru nanoparticles on Gd2O3 for efficient ammonia decomposition

Exploration of efficient Ru-based catalysts is significant for advancing the production of hydrogen from ammonia decomposition, which depends predominantly on the rational regulation of themetal-support interaction of Ru-based catalysts. Herein, highly dispersed Ru nanoparticles (NPs) on Gd2O3 (Ru/Gd2O3) are developed and applied for theNH3 decomposition reaction. By varying the reduction temperature, the activity of theRu/Gd2O3 catalyst can be remarkably improved. Characterization results reveal that the enhanced activity is associated with the strong metal‒support interaction (SMSI) induced formation of Gd2O3 overlayer on the Ru NPs. With a relatively low reduction temperature, the exposed Ru NPs possess relatively low activity toward NH3 decomposition. After high temperature activation treatment, the Gd2O3 overlayer coated Ru NPs show much enhanced intrinsic activity than that of the exposed Ru NPs. This study brings a facile strategy to modulate the catalytic performance of oxide supported Ru catalysts by regulating the SMSI of catalysts.

Exploring the superior mild temperature performance of nickel-infused fibrous titania silica for enhanced dry reforming of methane

Carbon (IV) oxide (CO2) and methane (CH4) contribute significantly to greenhouse gas emissions and global warming. One potential approach for reducing their environmental impact is transforming these gases into synthesis gas (CO + H2). This study illustrates the advancement of catalysts supported by fibrous titania silica (FTS), which have nickel loadings of 1%, 3%, and 5%. The FTS support, a modified variant of silica-titania, has a distinct fibrous structure and exhibits mesoporous material properties such as a type IV isotherm and an H1 hysteresis loop. After 72 h of operation, the 1Ni/FTS catalyst converted over 80% of CH4 and CO2 with low coke deposition, outperforming other catalysts. The bare FTS support had reduced CH4 conversion at 600°C, CO2 conversion at 650°C, and H2/CO ratio at 700°C. However, the 5Ni/FTS and 3Ni/FTS catalysts showed consistent increases in CH4 conversion at 600°C. The 1Ni/FTS catalyst, with a pore size of 7.39 nm, had strong metal-support interaction and moderate basicity sites, which helped with reactant dissociation and coke gasification. Despite the slightly higher CH4 conversion of the 3Ni/FTS catalyst and the high basicity of the 5Ni/FTS catalyst, the 1Ni/FTS catalyst demonstrated superior thermal stability and coking resistance, as evidenced by negligible weight loss during TGA analysis. Raman shifts revealed the presence of carbon synthesis and the buildup of disordered amorphous carbon. The Id/Ig ratios of FTS, 1Ni/FTS, 3Ni/FTS, and 5Ni/FTS were 1.01, 0.98, 1.01, and 1.01, respectively. The lower Id/Ig ratio of 1Ni/FTS suggests less disorder. The FTS support promises mild-temperature, carbon-neutral CH4 reforming with long-term catalytic applications. This study demonstrates the efficacy of FTS-supported catalysts in constructing long-term and efficient systems for converting greenhouse gasses.

Sustainable catalytic pathways for biofuel precursors: quantitative conversion of glucose to gluconic acid using Pt-Zn biochar catalyst

Achieving quantitative conversion of biomass-derived feedstocks under ambient environmental conditions (20°C, atmospheric air, 0.1 MPa) is a critical milestone for sustainability in chemical processes. Herein, the quantitative conversion of glucose to gluconic acid was accomplished under ambient environmental conditions without any additives using a Pt-Zn intermetallic nanoparticle-supported biochar catalyst prepared from raw rice straw (Pt-Zn/strawC) via a straightforward one-pot solvothermal reaction with ethylene glycol solvent. Spectroscopic analyses verified the formation of the Pt-Zn intermetallic alloy and confirmed strong electronic metal-support interactions. The Pt-Zn/strawC catalyst (Pt:Zn molar ratio of 1:6) was highly selective for the conversion of glucose to gluconic acid, whereas yields as high as 99.9% (98.9% gluconic acid, 1.0% glucaric acid) were reached at 20 oC under base-free and additive-free conditions. Isotope measurements and density functional theory revealed synergistic interactions in the Pt-Zn alloy, wherein the alloy tended to absorb glucose and active O2 into superoxide radical (O2·). This work demonstrates a chemocatalytic method that is practical for environmental conditions and provides a new avenue for sustainable conversion of lignocellulosic biomass to chemical products.

Support work-function dependent Fenton-like catalytic activity of Co single atoms for selective cobalt(IV)=O generation

In Fenton-like reactions, high-valent cobalt-oxo (CoIV=O) has attracted increasing interests due to high redox potential, long lifetime, and anti-interference properties, but its generation is hindered by the electron repulsion between the electron rich oxo- and cobalt centers. Here, we demonstrate CoIV=O generation from peroxymonosulfate (PMS) activation over cobalt single-atom catalysts (Co-SACs) using in-situ Co K-edge X-ray absorption spectra, and discern that CoIV=O generation is dependent on the support work-function (WF) due to the strong electronic metal-support interaction (EMSI). Supports with a high WF value like anatase-TiO2 facilitate the binding of PMS-terminal oxo-ligand to Co sites by extracting Co-d electrons, thus decreasing the generation barrier for the critical intermediate (Co-OOSO32−). The Co atoms anchored on anatase-TiO2 (Co-TiO2) exhibited enhanced CoIV=O generation and superior activity for sulfamethoxazole (SMX) degradation during PMS activation. The normalized steady-state concentration of CoIV=O in Co-TiO2/PMS system was three orders of magnitude higher than that of free radicals, and 1.3- to 11-fold higher than that generated in other Co-SACs/PMS systems. Co-TiO2/PMS sustained efficient removal of SMX with minimal Co2+ leaching under continuous flow operation, suggesting its attractive water purification potential. Overall, these results underscore the significance of support selection for enhanced generation of high-valent metal-oxo species and efficient PMS activation in supported metal SACs.

The study of design and performance improvement of catalysts for the stepwise production of bicyclohexane from benzene and cyclohexene

Bicyclohexane is a hydrogen storage reagent with high hydrogen density and low boiling point. Compared with the hydrogenation of biphenyl, the alkylation of benzene and cyclohexene to cyclohexylbenzene and hydrogenation is a promising way to prepare cyclohexane on a large scale. The research and development of high-efficiency cyclohexyl benzene hydrogenation catalyst should be further developed based on mature alkylation technology. This paper used an acidified USY molecular sieve to catalyze the alkylation of benzene and cyclohexene to cyclohexylbenzene, which achieved 100% conversion and selectivity. Furthermore, Pt/TiO2/γ-Al2O3 catalyst is prepared by pre-deposition TiO2 film of different thicknesses on γ-Al2O3 surface and then supported with platinum particles by Atomic layer deposition (ALD). The role of TiO2 film in improving the cyclohexylbenzene hydrogenation performance of the catalyst is studied. TEM, CO pulse chemisorption, CO-DRIFTs, quasi-in situ XPS, H-D exchange, and H2-TPR characterization show that compared with Pt/γ-Al2O3, TiO2 thin films on Pt/TiO2/γ-Al2O3 do not change the dispersion of Pt particles, but can form new Pt-TiO2 interactions. The hydrogenation performance of cyclohexylbenzene was improved by increasing the electron density and the proportion of planar active sites on the surface of platinum and reducing the energy barrier of hydrogen spillover. The research provides theoretical support for further bicyclohexane organic liquid hydrogen storage reagent development. The relevant metal-support interaction regulation strategy can be applied to the development of efficient catalysts for other aromatic molecules hydrogenation.

Regulating crystal phase of TiO2 to enhance catalytic activity of Ni/TiO2 for solar-driven dry reforming of methane

Ni/TiO2 catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO2 remains unclear. In this work, the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO2. Structural characterizations revealed that a distinct TiOx coating on the Ni nanoparticles (NPs) was evident for Ni/TiO2-700 catalyst due to strong metal-support interaction. It is observed that the TiOx overlayer gradually disappeared as the ratio of rutile/anatase increased, thereby enhancing the exposure of Ni active sites. The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH4, which led to the much elevated catalytic activity for Ni/ TiO2-950 in which rutile dominated. Therefore, the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio. Ni/TiO2-950, characterized by a predominant rutile phase, exhibited the highest DRM reactivity, with remarkable H2 and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h), respectively. These rates were approximately 257 and 130 times higher, respectively, compared to those obtained on Ni/TiO2-700 with anatase. This study suggests that the optimization of crystal structure of TiO2 support can effectively enhance the performance of photothermal DRM reaction.

Metal redispersion strategy for regeneration of sepiolite derived Co-phyllosilicate catalyst during glycerol steam reforming

Metal sintering and coke deposition have become main and irreversible obstacles for catalyst deactivation during H2 production from glycerol steam reforming (GSR). The regenerability of 15Co/SEP catalyst with a phyllosilicate derived strong metal-support interaction (SMSI) was probed by five successive GSR/regeneration cycles in order to evaluate the deactivation process and initial reactivity recovery. Two different regeneration methods were selected for the cycles: redox regeneration and combined regeneration. After the combined regeneration, reproducible GSR behaviors were obtained among the whole cycles. An almost recovery of initial activity (∼94 % of conversion and ∼ 73 % of H2 yield) and 50 h stability was noticed at 15Co/SEP-5 catalyst. By various characterizations analysis of fresh and spent catalysts, it was observed that irreversible metal sintering was aggravated by the redox regeneration, thus provoked initial activity loss and accelerated coking deactivation tendency. The combined regeneration achieved phyllosilicate recrystallization and metal exsolution/redispersion by a combination of NH4F-HNO3 assisted recrystallization and redox treatments, which ensured a small increase in Co0 nanoparticle size (13.2 nm vs. 15.3 nm) and coke deposition (23.9 wt% vs. 27.3 wt%) and inconspicuous change in the C1 species selectivity. The results suggested that 15Co/SEP catalyst is a promising candidate for commercialized GSR due to the favorable regenerability.

Engineering the electronic structure of Pt for selective hydrogenation of vanillin to vanillyl alcohol and p-cresol

The hydrogenation of vanillin stands as a pivotal platform reaction within biomass conversion processes, presenting a significant challenge in achieving controlled synthesis of different products. Here, we proffer different methodology for elaborately designing the electronic structure of Pt via regulating the strong metal-support interactions (SMSI) between Pt and Mo2TiC2, thereby facilitating the targeted synthesis of vanillyl alcohol (VA) and 2-methoxy-4-methylphenol (MMP) from vanillin. Appropriate H2 reduction can enhance the SMSI between Pt and Mo2TiC2, promoting the electron transfer from Mo2TiC2 to Pt, resulting in 200-Pt/Mo2TiC2 with 68.1 of Pt2+. However, the SR-Pt/Mo2TiC2 obtained through the galvanic replacement strategy possesses 64.7 % of Pt4+, which is attributed to the weaker spontaneous SMSI between Pt and Mo2TiC2. XPS adsorption experiments highlight the pivotal role of Pt2+ in facilitating the desorption of VA, resulting in the 200-Pt/Mo2TiC2 catalyst demonstrating exceptional selectivity towards VA (96 %). Meanwhile, SR-Pt/Mo2TiC2 showcases a predilection for the direct hydrogenation and deoxygenation of vanillin into MMP. This research not only marks the application of the MXene system to biomass conversion but also illuminates the relationship between the electronic structure of Pt and its selectivity towards VA and MMP.

Heterogeneously catalyzed reductive depolymerization of lignin to value-added chemicals.

Lignin is an abundant renewable source of aromatics, but its complex heterogeneous structure poses challenges for its depolymerization and valorization. Heterogeneously catalyzed reductive depolymerization (HCRD) has emerged as a promising approach, utilizing heterogeneous catalysts to facilitate selective bond cleavage in lignin and hydrogen transfer to stabilize the products under mild conditions. This review provides a comprehensive understanding of the hydrogen transfer mechanisms in HCRD involving different hydrogen sources including molecular hydrogen, alcohols, formic acid, etc., and the native hydrogen donor groups in lignin. Recent advances in catalyst design for efficient lignin depolymerization are systematically discussed, focusing on precious metal-based (Pt, Ru, Pd) and non-precious metal-based catalysts. Factors influencing catalyst performance, such as metal-support interactions, promoters, and synergistic effects, are highlighted. The diverse array of high-value aromatic chemicals obtained from HCRD is overviewed. Finally, the significance of HCRD in the context of lignin valorization and the development of integrated biorefineries is discussed, underscoring its potential to contribute to a sustainable bioeconomy.