Composite Catalyst Research Articles

Bimetallic MOF derived Cu3P/Co2P grown on coal-based carbon fibers as self-supporting electrocatalyst for enhanced hydrogen evolution

Transition metal phosphides (TMPs) are often considered as a cost-effective replacement for precious metal catalysts in hydrogen evolution reaction (HER). Herein, the fibers are produced by combining coal with electrospinning technology, and then undergoing a pre-oxidation process for transforming into pre-oxidized coal-based fibers. Subsequently, CuCo-metal organic framework (CuCo-MOF) is grown on the pre-oxidized coal-based fibers using solvothermal method, and the Cu3P/Co2P/coal-based carbon fibers (Cu3P/Co2P/C-CFs) composite catalyst is successfully fabricated by phosphating at low temperature and carbonizing at high temperature. The uniformly grown nanoparticles (NPs) on the surface of C-CFs enhance the electrochemically active area, while the electron transfer between Cu3P and Co2P effectively modulates the electronic structure, increasing the catalytic activity of the catalyst for HER. In addition, the flexible C-CFs not only serve as self-supporting electrode but also effectively inhibit the agglomeration of Cu3P/Co2P NPs. Remarkably, the overpotential of Cu3P/Co2P/C-CFs is 83 mV at 10 mA cm−2 current density for HER in 0.5 mol L−1 H2SO4 solution. This study presents promising strategies for the high value-added utilization of coal and the synthesis of highly effective non-precious metal catalysts.

Nitrogen–oxygen vacancy and S-scheme heterostructure synergistically enhance solar photocatalysis

Introducing vacancies and constructing S-scheme heterojunctions are promising approaches for enhancing photocatalytic activity. However, the application of this synergistic strategy to realize inexpensive and efficient photocatalysts remains challenging. In this study, a straightforward hydrothermal and calcination modification strategy was used to prepare a photocatalyst in which abundant nitrogen–oxygen vacancies were coupled with a Ce-ZnO@C-g-C3N4 composite with an S-scheme heterojunction. Under sunlight irradiation, the prepared composite achieves 98.3% and 86.4% degradation of methylene blue and ciprofloxacin, with degradation rate constants of 0.3464 and 0.0893 min−1, respectively. Compared with ZnO and g-C3N4, the degradation rates of methylene blue over the composite catalyst are 34.8 and 22.7 times higher, respectively, and those of ciprofloxacin are 2.4 and 4.9 times higher, respectively. Based on a detailed examination of the catalyst structure and photoelectric properties, the high photocatalytic efficiency is attributed to nitrogen–oxygen vacancies, an enhanced surface area, and synergistic S-scheme heterojunction effects. These factors broaden the spectral range, increase the number of active sites, and facilitate efficient charge transfer, thereby enhancing the photocatalytic reaction. This system demonstrates the feasibility of integrating doping and heterojunction formation to enhance photocatalytic performance synergistically.

Highly asymmetrically configured single atoms anchored on flame-roasting deposited carbon black as cathode catalysts for ultrahigh power density Zn-air batteries

Iron group element-based single atom (SA) catalysts are highly regarded as promising alternatives to commercial Pt/C for catalysis of oxygen reduction reaction (ORR). For applications in rechargeable zinc-air batteries (ZABs), achieving the necessary high catalytic efficiency of the SAs toward oxygen evolution reaction (OER) however remains a significant challenge. Here, highly asymmetrically configured Fe SAs created with N,S co-coordination and anchored on flame-roasting deposited carbon black (CB), Fe-N3S1/CB, are developed, achieving outstanding bifunctional oxygen catalytic efficiency, with an ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10), outperforming the (Pt/C+RuO2) composite catalyst (0.697 V). With a newly proposed binder-free composite air cathode design, the Fe-N3S1/CB based ZAB achieves an ultrahigh power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2, largely outperforming the (Pt/C+RuO2) based ZAB (225.9 mW cm-2 at 344.7 mA cm-2). Furthermore, the Fe-N3S1/CB based ZAB demonstrates excellent long-term stability, with only 8.2% decay in round-trip efficiency over 1000 (333.3 h) charge-discharge cycles at 10 mA cm-2. Density functional theory calculations elucidate that incorporation of sulfur into the coordination sphere of Fe facilitates the electrochemical dehydroxylation step for ORR and accelerates the electrochemical O2 desorption step for OER, thereby reducing the corresponding free energy differences on Fe SAs for largely enhanced catalytic efficiency.1. A large size hetero-atom element, sulfur, is introduced to create highly asymmetrically configured Fe single atoms for enhancements in catalytic efficiency toward both oxygen reduction reaction and oxygen evolution reaction, and a binder-free composite air cathode design is proposed to improve electrochemical performances of zinc-air batteries.2. An ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10) is achieved for the air cathode, and an ultrahigh discharge power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2 is acquired for the zinc-air battery.

Construction of the Co3O4/Nb2O5 Composite Catalyst with a Prickly Spherelike Architecture for CO2 Cycloaddition with Styrene Oxide.

A high-performance Nb2O5-based catalyst for the cycloaddition of CO2 with SO is designed by properly unifying the concepts of compositional regulation and architectural engineering. The Co3O4/Nb2O5 composite catalyst shows an intriguing prickly spherelike morphology. It exhibits a high styrene carbonate (SC) yield of 94.3% within 4 h (0.0824 mol g-1 h-1) under mild reaction conditions (0.4 MPa of CO2 and a reaction temperature of 90 °C) assisted by tetrabutylammonium bromide (TBAB). The coupling of Co3O4, which chemically interacts with Nb2O5, can effectively modulate the electronic structures of Nb2O5, constructing abundant acid/base sites for effectively activating the reactants and boosting the intrinsic activity. The high activity, cost-effectiveness, and good recyclability make the tailor-made Co3O4/Nb2O5 prickly spheres more appealing for commercial applications. This work offers new insights into designing and constructing well-integrated metal oxide composites for the cycloaddition of CO2 with an epoxide.

Efficient nitrate electroreduction to ammonia over copper catalysts supported on electron-delocalized covalent organic frameworks

Electrochemical nitrate reduction to ammonia (NRA) has recently emerged as a promising route to convert nitrate in wastewater into high-value-added products. Nevertheless, the development of NRA has been hampered by reaction involves multi-proton and electron transfer, posing a low Faradaic efficiency (FE). Here, we develop a composite catalyst of Cu/Cu2O nanoparticles on covalent organic frameworks (COFs) with highly ordered and porous topological structures. The high electron delocalization feature of COFs arising from their two-dimensional structure and rich π-bond increase the electron density of Cu active site, which is benefit for the adsorption and activation of NO3–. The composite catalyst can deliver a satisfactory FE of 95% and a yield rate of 3.4 mmol/h mg−1 for ammonia synthesis. Experimental and theoretical studies both reveals that the COF support can effectively increase the local concentration of NO3– at catalyst surface and decrease the energy barrier, leading to superior NRA performance.

Catalytic pyrolysis of Padina sp. with ZSM-5 and Amberlyst-15 catalysts to produce aromatic-rich bio-oil

The growing demand for renewable energy has increased interest in bio-oil production from biomass, particularly through catalytic co-pyrolysis. However, research on marine biomass like Padina sp. is limited. This study investigates the catalytic co-pyrolysis of Padina sp. using ZSM-5 and Amberlyst-15 catalysts to enhance aromatic-rich bio-oil production. Systematic experiments were conducted with varying catalyst loadings (1 %, 2 %, and 3 %) and temperatures (400 °C, 500 °C, and 600 °C). GC/MS analysis revealed that Amberlyst-15 at 600 °C and 3 % loading achieved a 65 % aromatic hydrocarbon yield, surpassing ZSM-5, which reached 50 %. Additionally, the highest conversion efficiency, 50 %, was attained with Amberlyst-15 at 500 °C and 3 % loading. These findings highlight the viability of Padina sp. as a renewable biofuel source and emphasize the importance of catalyst selection and process optimization in refining bio-oil production techniques, suggesting that further improvements in catalyst compositions and parameters could advance sustainable bio-oil production for renewable energy.

Regulating Contact-Electro-Catalysis Using Polymer/Metal Janus Composite Catalysts.

Interfacial contact electrification can catalyze redox reactions through a process called contact-electro-catalysis (CEC). The two main reaction paths for producing reactive oxygen species via CEC are the water oxidation reaction (WOR) and the oxygen reduction reaction (ORR). Herein, we designed a polymer/metal Janus composite catalyst that regulated the reaction rates of the WOR and ORR based on the catalyst composition. The ORR was preferentially enhanced when the polymer was negatively charged during contact electrification, while the WOR was preferentially enhanced when the polymer was positively charged. This phenomenon was observed for various conductive materials. The increase in the enhancement of the reaction rates depended on the conductivity and work function of the metal. We expect that this efficient CEC method can form a universal strategy for improving the performance of existing catalysts, as contact electrification is common in nature.

Core-shell structured composite high-efficiency catalyst Co@Pd/TiO2 with a compressed-strain Pd shell for the direct synthesis of H2O2

Direct synthesis of H2O2 from H2 and O2 still faces the dilemma of low selectivity and productivity due to the O-O bond dissociation. To expedite the resolution of this issue, we introduce a core–shell structured catalyst Co@Pd/TiO2 with a compressed-strain Pd shell. The Co@Pd/TiO2 catalyst demonstrates a superior H2O2 productivity of 6.95 × 103 mmol·gPd-1·h−1 and H2O2 selectivity of 98.1 %, with enhancements of over 192 % and 139 %, respectively, when compared to Pd/TiO2. The construction of the compressed-strain Pd shell on the Co@Pd/TiO2 catalyst induces a winder width (wd) and a lower center (εd) of the Pd d-band, allowing the Co@Pd/TiO2 catalyst to achieve the following benefits for improving H2O2 selectivity and productivity: (1) Reducing the degree of electron back-donation to O2* (* denotes adsorbed state, the same below), thus inhibiting the cleavage of the O-O bond in O2*; (2) Showing a weaker Pd-O bond strength, which stabilizes the OOH* species and suppresses the breakage of the O-O bond therein; (3) Weakening the interaction between the catalyst and chemical substances, thereby restraining H2O2 degradation.

Iron hematite-magnetite composite supported on mesoporous SBA-15 synthesized by using silica from cogon grass as a solid catalyst in phenol hydroxylation

Phenol hydroxylation involves the oxidation of phenol (C6H5OH) using hydrogen peroxide (H2O2) to yield benzenediol (C6H4(OH)2), mainly catechol (CTL) and hydroquinone (HQ). These products are in high demand in the pharmaceuticals industry sector. Thus, it is still worth investigating for further improvement in terms of heterogeneous iron catalysts. Herein, this research focuses on an iron hematite (Fe2O3)-magnetite (Fe3O4) composite catalyst supported on SBA-15 using silica from cogon grass for phenol hydroxylation. The extracted silica exhibited a fine white powder appearance and an amorphous structure, used as a silica source for SBA-15 synthesis. After catalyst preparation, the presence of Fe2O3, Fe3O4, and Fe2O3-Fe3O4 composite on SBA-15 was confirmed by using X-ray absorption near-edge structure (XANES). X-ray photoelectron spectroscopy (XPS) analysis provided insights into the surface of the catalyst, revealing that Fe2O3-Fe3O4/SBA-15 had the highest dispersion of iron species. In terms of catalytic performance, Fe2O3-Fe3O4/SBA-15 displayed the highest conversion of 88 % and HQ selectivity of 46 % compared with lone Fe3O4/SBA-15 or Fe2O3 /SBA-15. The magnetic separation approach demonstrated the easy separation of catalysts containing Fe3O4. Reusability studies showed that Fe2O3-Fe3O4/SBA-15 maintained its activity up to the 4th cycle, suggesting minimized iron leaching compared to Fe3O4/SBA-15. Overall, this study provides insights into the catalytic performance of phenol hydroxylation and iron-based catalysts, emphasizing the potential of Fe2O3-Fe3O4/SBA-15 as an effective and reusable catalyst.

Selective recovery of platinum from spent catalysts to fabricate platinum/amorphous manganese oxide/corrugated silica carrier for formaldehyde removal

The efficient recovery and reutilization of spent Pt catalysts have two huge challenges in the metallurgical and chemical industries. Herein, platinum was selectively retrieved from spent Pt/γ-Al2O3 catalysts by a microwave-assisted aqua regia digestion strategy, and the as-obtained platinum extract was utilized to prepare a novel Pt/amorphous MnOx/corrugated silica carrier (Pt/MnOx/CSC) catalyst for formaldehyde removal. To decrease consumption of toxic aqua regia, the γ-Al2O3 in the spent catalysts was converted to chemically stabile α-Al2O3 via high-temperature calcination. The high Pt leaching efficiency of 98.31% was achieved at a digestion temperature of 110oC and aqua regia concentration of 40vol%. However, the high leaching temperatures and aqua regia concentrations caused the part dissolution of α-Al2O3, and thus decreased the Pt leaching efficiency. The CSC in the Pt/MnOx/CSC catalysts served as a support, while both the Pt nanoparticles and amorphous MnOx microspheres acted as active catalysts. The synergistical effects between the Pt and amorphous MnOx endowed the composite catalysts with excellent catalytic activity, and the HCHO removal efficiency reached 100% even after five cycle tests. On the one hand, the nanostructured MnOx microspheres provided great surface areas and rich oxygen vacancies for heterogeneous catalysis. On the other hand, the Pt nanoparticles not only enhanced the low-temperature reducibilities of MnOx, but also decreased the apparent activation energies of HCHO catalytic oxidation. This work provided a new strategy for the selective recovery of platinum from spent catalysts and the reutilization of Pt-based catalysts for the HCHO thermal catalytic oxidation.

Synthesis of isolated ZnO nanorods on introducing g-C3N4 for improved photoelectrocatalytic methanol production by CO2 reduction

The photoelectrocatalytic (PEC) CO2 reduction into fuels has been developed as a prospective approach to resolve the environmental and energy concerns. Herein, a composite catalyst comprising ZnO nanorods dispersed on the g-C3N4 surface (g-C3N4/ZnO) was successfully obtained by simple ZnO seed layer formation and then hydrothermal processes. The synthesized and characterized g-C3N4/ZnO catalytic composite showed 2.8 times enhanced photocurrent density at −1 V applied potential than the bare g-C3N4. The g-C3N4/ZnO catalyst exhibited 2.86 times enhanced the PEC CO2 reduction to methanol than the prepared bare ZnO catalyst. The catalyst’s enhanced the PEC CO2 reduction performance was ascribed to the high surface area, and higher generation and lower recombination of e−/h+ pairs. For the first time, this study showed the enhanced methanol production by the PEC reduction of CO2 over the prepared g-C3N4/ZnO catalytic composite.

Charge transfer optimization: Role of Cu-graphdiyne/NiCoMoO4 S-scheme heterojunction and Ohmic junction

The effective separation ability of photogenic support plays a crucial role in catalytic hydrogen production. The establishment of heterojunction structure is an effective means to overcome the limited carrier separation ability of some single catalysts. In this paper, Cu, Graphdiyne (GDY) and NiCoMoO4 were successfully coupled to construct a composite photocatalyst NCY-15 ​%. The addition of sheet GDY effectively prevented the aggregation of NiCoMoO4, increased the number of active sites, and enhanced the light-trapping ability of the composite catalyst. The synergistic interaction of S-scheme heterojunction and Ohmic junction heterojunctions between Cu, GDY and NiCoMoO4 provides a unique transfer pathway for electrons, facilitating the rapid separation of photogenerated carriers and accelerating electron transfer, while retaining electrons with strong reducing capacity to participate in hydrogen production, thereby increasing the hydrogen evolution rate. This provides a new way for the development of GDY based photocatalysts.

Ag-modified CuO-Fe2O3 composite catalysts for low-temperature NH3-SCO

A series of CuFe and Ag-modified CuFe composite catalysts were prepared for low-temperature selective catalytic oxidation of ammonia (NH3-SCO). Significant synergistic effects existed between Cu and Fe oxides in the CuFe(7:12) catalyst for catalyzing NH3 oxidation. Loading 6 wt.% Ag over CuFe(7:12) further enhanced NH3 conversion and N2 selectivity. At 200 °C, NH3 conversion and N2 selectivity reached 97.1 % and 79.3 %, respectively, over 6Ag/CuFe(7:12). Besides the exceptional catalytic effects of Ag species, the increased surface area, formation of CuFe2O4, improved reducibility of Cu and Fe oxides, and increased acid sites due to the composite of Cu and Fe and modification with Ag contributed to the superior performance of the 6Ag/CuFe(7:12) catalyst in NH3-SCO. In-situ DRIFTS results showed that NH3 oxidation might follow the internal selective catalytic reduction mechanism: NH3 was dehydrogenated and oxidized to NOx and nitrate species, and the formed NOx and nitrate species were reduced by the remaining NH3, −NH2 and −NH species to N2 and H2O. Loading Ag over CuFe(7:12) suppressed the formation of NO and NO2 but promoted that of N2O during NH3 oxidation, which could be attributed to the enhanced formation and decomposition of NH4NO3 in the presence of Ag.

Catalytic pyrolysis of hydrolyzed lignin using HZSM-5/MCM-41 supported transition-metal to produce monocyclic aromatic hydrocarbons

Hydrolyzed lignin (HL), one kind of organic solid wastes, comes from the production of hydrolysis of lignocellulosic biomass for high-value chemicals, unsuitable treatment of which not only meaning the waste of resources but also resulting environmental pollution. The pyrolysis of HL has the problem of high oxygen-containing compounds and low hydrocarbons in the products. The HZSM-5/MCM-41 (HM) meso-microporous composite catalyst, containing nickel and molybdenum, was synthesized through impregnation to enhance the production of monocyclic aromatic hydrocarbons (MAHs) during the in-situ catalytic pyrolysis of hydrolyzed lignin. Different transition metals loaded on composite molecular sieves were prepared for comparison. The relationship between catalyst structure and pyrolysis efficiency was studied based on characterization techniques including SEM, BET, and XRD. This study investigated the catalytic properties of modified composite molecular sieves with Ni and Mo at different loaded ratios on the pyrolysis of hydrolyzed lignin. Results indicated that HM loaded with different metals had different catalytic pyrolysis selectivity. The relative yield of MAHs on 3 %Ni-HM was the highest, at 27.78 %, while that of phenolic on 5 %Mo-HM was 51.02 %. Thus, by modifying the co-loading ratios between Ni and Mo, the combined catalytic pyrolysis of hydrolyzed lignin was performed, achieving a 39.24 % yield of MAHs on the catalyst Mo1Ni2-HM, markedly surpassing the 17.69 % yield from unaltered HZSM-5/MCM-41. In addition, the improvement of active sites was caused by transition metals loaded and the synergistic effect between bimetals enhanced the catalytic activity and stability. HZSM-5/MCM-41 loaded with metal oxides promoted the depolymerization of macromolecules in the intermediate products of pyrolysis, and thus improved the relative yield of MAHs among pyrolysis products of hydrolyzed lignin.

Hydrogen production via steam reforming of methanol using Cu/ZnO/Al2O3: Effect of catalyst synthesis method and Cu to Zn molar ratio on physico-chemical properties and catalytic performance

This research investigates the steam reforming of methanol (SRM) using Cu/ZnO/Al2O3 catalysts synthesized via three distinct methods: coprecipitation, hydrothermal, and sol-gel methods. A comprehensive analysis of the catalysts' physicochemical, morphological, and thermal properties was conducted, and their catalytic performances were compared. The coprecipitation method yielded catalysts with desirable catalytic properties, including high specific surface area, increased Cu0 area, increased Cu dispersion, and improved reducibility, leading to the highest catalytic performance compared to the other methods tested. These catalysts exhibited the highest methanol conversions of 91.5% and H2 yield of 90.9%, with a low CO selectivity of 0.61% at 280 °C. In contrast, catalysts synthesized via hydrothermal and sol-gel methods showed lower methanol conversions of 39.2% and 73.5%, H2 yields of 39.0% and 72.7%, and CO selectivity of 1.46% and 0.91%, respectively, at the same temperature. Further investigation of the coprecipitated catalysts involved varying the Cu/Zn molar ratios. The results revealed a noteworthy influence Cu/Zn ratio on the characterization results and catalytic performance. Notably, a Cu/ZnO/Al2O3 catalyst with a Cu to Zn ratio of 1 emerged as the optimal catalyst composition, demonstrating the highest catalytic performance for SRM.

Inverse ceria-nickel catalyst for enhanced C-O bond hydrogenolysis of biomass and polyether.

Regulating interfacial electronic structure of oxide-metal composite catalyst for the selective transformation of biomass or plastic waste into high-value chemicals through specific C-O bond scission is still challenging due to the presence of multiple reducible bonds and low catalytic activity. Herein, we find that the inverse catalyst of 4CeOx/Ni can efficiently transform various lignocellulose derivatives and polyether into the corresponding value-added hydroxyl-containing chemicals with activity enhancement (up to 36.5-fold increase in rate) compared to the conventional metal/oxide supported catalyst. In situ experiments and theoretical calculations reveal the electron-rich interfacial Ce and Ni species are responsible for the selective adsorption of C-O bond and efficient generation of Hδ- species, respectively, which synergistic facilitate cleavage of C-O bond and subsequent hydrogenation. This work advances the fundamental understanding of interfacial electronic interaction over inverse catalyst and provides a promising catalyst design strategy for efficient transformation of C-O bond.

Pyrolysis of hyphaene thebaica shell over ceramic tile dust-derived catalysts and assessment of the produced bio-oil

The purpose of this study is to demonstrate the potential of ceramic tile dust (CTD)-derived ZSM-5 zeolite (CZ) and its monodispersed composite with metal oxides (MgO and Fe2O3) in the catalytic pyrolysis of hyphaene thebaica shell (HTS). The HTS was pyrolysed in a Fixed-bed reactor at 400–600 °C, and 100–300 mL/min N2 flowrate. The maximum bio-oil production of 32 % was obtained at 500 °C and 150 mL/min N2 flowrate, with bio-oils containing 50 % acid and octadecenoic acids, as well as esters, phenols, aldehydes, ketones, ethers, aromatics, and hydrocarbons. A carboxymethyl cellulose templating agent was employed for the mesoporous zeolite synthesis from CTD. This resulted in the mesoporous zeolite with a predominant ZSM-5 crystal phase, exhibiting pore diameters ranging from 1.8-6 nm, 229 m2/g surface area and 1145 μmol/g total acidity. The catalytic pyrolysis of HTS was conducted using the ZSM-5 zeolite (CZ) and metal-oxide (MgO, Fe2O3, and Fe2O3/FeO) modified CZ, as monodispersed composite catalysts. Under best thermal pyrolysis conditions, CZ-Fe2O3, CZ-MgO, and CZ-Fe2O3/MgO demonstrated 22–23 % bio-oil yields. Notably, the CZ-Fe2O3/MgO catalyst exhibited the highest hydrocarbon yield at 16 %, while the CZ-MgO favoured the production of phenolics, esters, and alcohols. CZ-MgO also displayed the highest coking level at 7.5 %, indicating faster deactivation than the other catalysts. The synthesised catalysts exhibited remarkable catalytic activity, resulting in a notable improvement in the quality of bio-oils obtained from the intermediate pyrolysis of hyphaene thebaica shells in a fixed-bed reactor.

Bi-functional hydrogen tungsten bronze/carbon composite catalysts towards biomass conversion and solar water purification

We presented a novel bi-functional catalyst composed of HxWO3 and carbon composites, which exhibits excellent catalytic activity in biomass conversion and has the ability to effectively purify water via a wide range of wavelengths in the light spectrum. The HxWO3/carbon composites were effectively produced from commercially available monoclinic tungsten trioxide (WO3) and polypropylene (PP) powders to a single-step mechanochemical reaction employing high-energy ball milling. We systemically investigated how different synthesis parameters, such as rotation speed, processing duration, and ball diameter, affect the mechanochemically-induced phase transformation to either tetragonal or cubic HxWO3 during planetary ball milling. The crystal phase of HxWO3 was controllable by altering the total impact energy in the ball milling. In addition, real-time monitoring of the pressure increment inside the pot and evaluation of the evolved gas revealed the degassing behavior through the oxidative degradation of PP assisted by WO3. The CV and Rietveld analysis proved that HxWO3 exhibited significant enhancement by two orders of magnitude in the rate of H+ diffusion compared to monoclinic WO3. This enhancement would be attributed to the expansion of a mechanically-formed tunnel along the a-axis, which facilitates the migration of H+ ions. The HxWO3/carbon composites performed approximately 12-fold higher efficiency in generating soluble solids (glucose and furfural derivatives) compared to untreated WO3 through the catalytic hydrolysis of cellulose, owing to the enhanced Brønsted acidity. Moreover, the composite particles showed broad light absorption in the UV–Vis–NIR range and demonstrated a considerable enhancement of over three orders of magnitude in the photocatalytic degradation of methyl orange pollutants when exposed to NIR and visible light.

Experimental and computational investigations of biodiesel production from castor oil using Li-doped salmon fish bone-supported lanthanum oxide catalyst in a micro-reactor

Ensuring efficient and sustainable biodiesel production is essential for addressing environmental concerns and meeting global energy demands. This study aims to optimize the transesterification of castor oil through the development of a distinctive Li-doped-salmon fish bone (SFB)-supported La2O3 composite catalyst within a micro-reactor setup. The optimal catalyst (3 % Li/SFB-La) was thoroughly evaluated for its physicochemical features employing a range of characterization techniques, including XRD, XPS, BET, FESEM, TEM, TGA/DSC, and FT-IR. According to density functional theory (DFT) calculations, the function of Li dopants, which have a lower electronegativity (0.98) compared to La (1.1), is to enhance the charge transfer capability of La sites, thereby increasing their reactivity with triglycerides. In the interim, we determined the optimized reaction conditions: a 6:1 methanol/oil molar ratio and a 5 wt % catalyst loading at 338 K. Under these parameters, an impressive 99.38 % conversion was achieved within 1.5 h. Furthermore, the 3 % Li/SFB-La composite catalyst exhibited remarkable stability, retaining its high activity throughout 7 cycles without any significant loss of efficacy. Moreover, the transesterification reaction kinetics were thoroughly investigated, revealing a reaction rate constant of 1.17 h−1 and an activation energy of 14.46 kJ/mol.

Boosting synergistic effects between PtGe nanoalloys and 2D materials for PEMFC applications

In the present work we have investigated the stability, CO poisoning tendency and HOR and ORR activities of small-sized monometallic Pt and bimetallic PtGe nanoclusters deposited on a series of 2D materials. By means of global minima search and mechanistic studies at the density functional theory (DFT) level with continuum implicit solvent, a screening of size, composition and support material has been carried out to obtain the optimal catalyst compositions that may boost the catalytic performance. Alloying and support effects work in two directions. On the one hand, the support increases the stability and modifies the electronic structure of the cluster via metal-support interaction. On the other hand, the cluster can change the electronic properties and catalytic activity of the support, which can be modulated with its size and composition. In addition, the 2D support assists pure Pt clusters in reducing the propensity to undergo CO poisoning, which can be further reduced by Ge alloying. This effect can be exploited to the point that the interaction with CO is not even favorable, as in Pt5Ge5/germanene, thus completely inhibiting the CO poisoning on the catalyst. Regarding the catalytic activities, all the catalysts studied in this work yield too high overpotentials for the ORR in acidic conditions, due to the presence of too oxophilic active sites which results in the overbinding of oxygenated species. However, the combination of Ge alloying and 2D support yield remarkable results in the HOR performance. The simultaneous tailoring of catalyst composition and support is demonstrated to be an effective strategy to successfully adjust the catalytic properties.