Optimized Pt-Co Alloy Nanoparticles for Reverse Water-Gas Shift Activation of CO2.

Different Co contents were used to tune bimetallic Pt-Co nanoparticles with a diameter of 8 nm, resulting in Pt:Co ratios of 3.54, 1.51, and 0.96. These nanoparticles were then applied to the MCF-17 mesoporous silica support. The synthesized materials were characterized with HR-TEM, HAADF-TEM, EDX, XRD, BET, ICP-MS, in situ DRIFTS, and quasi in situ XPS techniques. The catalysts were tested in a thermally induced reverse water-gas shift reaction (CO2:H2 = 1:4) at atmospheric pressure in the 200-700 °C temperature range. All bimetallic Pt-Co particles outperformed the pure Pt benchmark catalyst. The nanoparticles with a Pt:Co ratio of 1.51 exhibited 2.6 times higher activity and increased CO selectivity by 4% at 500 °C. Experiments proved that the electron accumulation and alloying effect on the Pt-Co particles are stronger with higher Co ratios. The production of CO followed the formate reaction pathway on all catalysts due to the face-centered-cubic structure, which is similar to the Pt benchmark. It is concluded that the enhanced properties of Co culminate at a Pt:Co ratio of 1.51 because decreasing the ratio to 0.96 results in lower activity despite having more Co atoms available for the electronic interaction, resulting in the lack of electron-rich Pt sites.

High-Entropy Oxides: A New Frontier in Photocatalytic CO2 Hydrogenation.

Herein, we investigate the potential of nanostructured high-entropy oxides (HEOs) for photocatalytic CO2 hydrogenation, a process with significant implications for environmental sustainability and energy production. Several cerium-oxide-based rare-earth HEOs with fluorite structures were prepared for UV-light driven photocatalytic CO2 hydrogenation toward valuable fuels and petrochemical precursors. The cationic composition profoundly influences the selectivity and activity of the HEOs, where the Ce0.2Zr0.2La0.2Nd0.2Sm0.2O2-δ catalyst showed outstanding CO2 activation (14.4 molCO kgcat-1 h-1 and 1.27 molCH3OH kgcat-1 h-1) and high methanol and CO selectivity (7.84% CH3OH and 89.26% CO) under ambient conditions with 4 times better performance in comparison to pristine CeO2. Systematic tests showed the effect of a high-entropy system compared to midentropy oxides. XPS, in situ DRIFTS, as well as DFT calculation elucidate the synergistic impact of Ce, Zr, La, Nd, and Sm, resulting in an optimal Ce3+/Ce4+ ratio. The observed formate-routed mechanism and a surface with high affinity to CO2 reduction offer insights into the photocatalytic enhancement. While our findings lay a solid foundation, further research is needed to optimize these catalysts and expand their applications.

Pt/MnO Interface Induced Defects for High Reverse Water Gas Shift Activity.

The implementation of supported metal catalysts heavily relies on the synergistic interactions between metal nanoparticles and the material they are dispersed on. It is clear that interfacial perimeter sites have outstanding skills for turning catalytic reactions over, however, high activity and selectivity of the designed interface-induced metal distortion can also obtain catalysts for the most crucial industrial processes as evidenced in this paper. Herein, the beneficial synergy established between designed Pt nanoparticles and MnO in the course of the reverse water gas shift (RWGS) reaction resulted in a Pt/MnO catalyst having ≈10 times higher activity compared to the reference Pt/SBA-15 catalyst with >99 % CO selectivity. Under activation, a crystal assembly through the metallic Pt (110) and MnO evolved, where the plane distance differences caused a mismatched-row structure in softer Pt nanoparticles, which was identified by microscopic and surface-sensitive spectroscopic characterizations combined with density functional theory simulations. The generated edge dislocations caused the Pt lattice expansion which led to the weakening of the Pt-CO bond. Even though MnO also exhibited an adverse effect on Pt by lowering the number of exposed metal sites, rapid desorption of the linearly adsorbed CO species governed the performance of the Pt/MnO in the RWGS.

Highly Porous Polymer Beads Coated with Nanometer-Thick Metal Oxide Films for Photocatalytic Oxidation of Bisphenol A.

Highly porous metal oxide-polymer nanocomposites are attracting considerable interest due to their unique structural and functional features. A porous polymer matrix brings properties such as high porosity and permeability, while the metal oxide phase adds functionality. For the metal oxide phase to perform its function, it must be fully accessible, and this is possible only at the pore surface, but functioning surfaces require controlled engineering, which remains a challenge. Here, highly porous nanocomposite beads based on thin metal oxide nanocoatings and polymerized high internal phase emulsions (polyHIPEs) are demonstrated. By leveraging the unique properties of polyHIPEs, i.e., a three-dimensional (3D) interconnected network of macropores, and high-precision of the atomic-layer-deposition technique (ALD), we were able to homogeneously coat the entire surface of the pores in polyHIPE beads with TiO2-, ZnO-, and Al2O3-based nanocoatings. Parameters such as nanocoating thickness, growth per cycle (GPC), and metal oxide (MO) composition were systematically controlled by varying the number of deposition cycles and dosing time under specific process conditions. The combination of polyHIPE structure and ALD technique proved advantageous, as MO-nanocoatings with thicknesses between 11 ± 3 and 40 ± 9 nm for TiO2 or 31 ± 6 and 74 ± 28 nm for ZnO and Al2O3, respectively, were successfully fabricated. It has been shown that the number of ALD cycles affects both the thickness and crystallinity of the MO nanocoatings. Finally, the potential of ALD-derived TiO2-polyHIPE beads in photocatalytic oxidation of an aqueous bisphenol A (BPA) solution was demonstrated. The beads exhibited about five times higher activity than nanocomposite beads prepared by the conventional (Pickering) method. Such ALD-derived polyHIPE nanocomposites could find wide application in nanotechnology, sensor development, or catalysis.

Plasmonic Effect of Gold-Patchy Silica Nanoparticles on Green Light-Photopolymerizable Dental Resin.

A low ratio of polymerization is a major problem in resin-based composites. In this paper, the plasmonic effect of gold-covered silica nanoparticles on the physicochemical and mechanical properties of bisphenol A diglycidyl dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) green light-photopolymerizable dental resin was investigated at an intensity of 1.4 mW/cm2 for 40 s. Transmission electron microscopy (TEM) showed silica of about 350 nm covered with 12-15 nm gold nanoparticles (Au NPs) at 100% nominal coverage. Five different concentrations of bare and patchy silica particles were used; in the latter composite, the calculated Au wt% were 0.0052 wt%, 0.0104 wt%, 0.0208 wt%, 0.04160 wt%, and 0.0823 wt%. The plasmon peak of patchy silica-filled nanocomposite overlapped with the absorption of Irgacure 784 photoinitiator and green LED light emission peak. The effect of plasmon-enhanced polymerization achieved with green light illumination was analyzed using diametral tensile strength (DTS), differential scanning calorimetry (DSC), surface plasmon resonance imaging (SPRi), and degree of conversion (DC) based on Raman spectroscopy. The values of the Au NP with 0.0208 wt% was found to be maximum in all the measured data. Based on our result, it can be concluded that the application of patchy silica particles in dental resin can improve the polymerization ratio and the mechanical parameters of the composite.

Can the new energy vehicles (NEVs) and power battery industry help China to meet the carbon neutrality goal before 2060?

China is working to boost the manufacture, market share, sales, and use of NEVs to replace fuel vehicles in transportation sector to get carbon reduction target by 2060. In this research, using Simapro life cycle assessment software and Eco-invent database, the market share, carbon footprint, and life cycle analysis of fuel vehicles, NEVs, and batteries were calculated from the last five years to next 25 years, with a focus on the sustainable development. Results indicate globally, China had 293.98 m vehicles and 45.22% worldwide highest market share, followed by Germany with 224.97 m and 42.22% shares. Annually China's NEVs production rate is 50%, and sales account for 35%, while the carbon footprint will account for 5.2 E+07 to 4.89 E+07 kgCO2e by 2021-2035. The power battery production 219.7 GWh reaches 150%-163.4%, whereas carbon footprint values in production and use stage of 1 kWh of LFP 44.0 kgCO2eq, NCM-146.8 kgCO2eq, and NCA-370 kgCO2eq. The single carbon footprint of LFP is smallest at about 5.52 E+09, while NCM is highest at 1.84 E+10. Thus, using NEVs, and LFP batteries will reduce carbon emissions by 56.33%-103.14% and 56.33% or 0.64 Gt to 0.006 Gt by 2060. LCA analysis of NEVs and batteries at manufacturing and using stages quantified the environmental impact ranked from highest to lowest as ADP > AP > GWP > EP > POCP > ODP. ADP(e) and ADP(f) at manufacturing stage account for 14.7%, while other components account for 83.3% during the use stage. Conclusive findings are higher sales and use of NEVs, LFP, and reduction in coal-fired power generation from 70.92% to 50%, and increase in renewable energy sources in electricity generation expectedly will reduce carbon footprint by 31% and environmental impact on acid rain, ozone depletion, and photochemical smog. Finally, to achieve carbon neutrality in China, the NEVs industry must be supported by incentive policies, financial aid, technological improvements, and research and development. This would improve NEV's supply, demand, and environmental impact.

CO2 Conversion on N-Doped Carbon Catalysts via Thermo- and Electrocatalysis: Role of C-NO x Moieties.

N-doped carbon (N-C) materials are increasingly popular in different electrochemical and catalytic applications. Due to the structural and stoichiometric diversity of these materials, however, the role of different functional moieties is still controversial. We have synthesized a set of N-C catalysts, with identical morphologies (∼27 nm pore size). By systematically changing the precursors, we have varied the amount and chemical nature of N-functions on the catalyst surface. The CO2 reduction (CO2R) properties of these catalysts were tested in both electrochemical (EC) and thermal catalytic (TC) experiments (i.e., CO2 + H2 reaction). CO was the major CO2R product in all cases, while CH4 appeared as a minor product. Importantly, the CO2R activity changed with the chemical composition, and the activity trend was similar in the EC and TC scenarios. The activity was correlated with the amount of different N-functions, and a correlation was found for the -NO x species. Interestingly, the amount of this species decreased radically during EC CO2R, which was coupled with the performance decrease. The observations were rationalized by the adsorption/desorption properties of the samples, while theoretical insights indicated a similarity between the EC and TC paths.

Efficient charge separation and improved photocatalytic activity in Type-II & Type-III heterojunction based multiple interfaces in BiOCl0.5Br0.5-Q: DFT and Experimental Insight.

The nanostructured, inner-coupled Bismuth oxyhalides (BiOX0.5X'0.5; X, X' = Cl, Br, I; X≠X') heterostructures were prepared using Quercetin (Q) as a sensitizer. The present study revealed the tuning of the band properties of as-prepared catalysts. The catalysts were characterized using various characterization techniques for evaluating the superior photocatalytic efficiency and a better understanding of elemental interactions at interfaces formed in the heterojunction. The material (BiOCl0.5Br0.5-Q) reflected higher degradation of MO (about 99.85%) and BPA (98.34%) under visible light irradiation than BiOCl0.5I0.5-Q and BiOBr0.5I0.5-Q. A total of 90.45 percent of total organic carbon in BPA was removed after visible light irradiation on BiOCl0.5Br0.5-Q. The many-fold increase in activity is attributed to the formation of multiple interfaces between halides, conjugated π-electrons and multiple -OH groups of quercetin (Q). The boost in degradation efficiency can be attributed to the higher surface area, 2-D nanostructure, inhibited electron-hole recombination, and appropriate band-gap of the heterostructure. Photo-response of BiOCl0.5Br0.5-Q is higher compared to BiOCl0.5I0.5-Q and BiOBr0.5I0.5-Q, indicating better light absorption properties and charge separation efficiency in BiOCl0.5Br0.5-Q due to band edge position. First-principles Density Functional Theory (DFT) based calculations have also provided an insightful understanding of the interface formation, physical mechanism, and superior photocatalytic performance of BiOCl0.5Br0.5-Q heterostructure over other samples.

Sol-Gel Synthesis of Ceria-Zirconia-Based High-Entropy Oxides as High-Promotion Catalysts for the Synthesis of 1,2-Diketones from Aldehyde.

Efficient Lewis-acid-catalyzed direct conversion of aldehydes to 1,2-diketones in the liquid phase was enabled by using newly designed and developed ceria-zirconia-based high-entropy oxides (HEOs) as the actual catalysts. The synergistic effect of various cations incorporated in the same oxide structure (framework) was partially responsible for the efficiency of multicationic materials compared to the corresponding single-cation oxide forms. Furthermore, a clear, linear relationship between the Lewis acidity and the catalytic activity of the HEOs was observed. Due to the developed strategy, exclusively diketone-selective, recyclable, versatile heterogeneous catalytic transformation of aldehydes can be realized under mild reaction conditions.

Bioplastics and Carbon-Based Sustainable Materials, Components, and Devices: Toward Green Electronics.

The continuously growing number of short-life electronics equipment inherently results in a massive amount of problematic waste, which poses risks of environmental pollution, endangers human health, and causes socioeconomic problems. Hence, to mitigate these negative impacts, it is our common interest to substitute conventional materials (polymers and metals) used in electronics devices with their environmentally benign renewable counterparts, wherever possible, while considering the aspects of functionality, manufacturability, and cost. To support such an effort, in this study, we explore the use of biodegradable bioplastics, such as polylactic acid (PLA), its blends with polyhydroxybutyrate (PHB) and composites with pyrolyzed lignin (PL), and multiwalled carbon nanotubes (MWCNTs), in conjunction with processes typical in the fabrication of electronics components, including plasma treatment, dip coating, inkjet and screen printing, as well as hot mixing, extrusion, and molding. We show that after a short argon plasma treatment of the surface of hot-blown PLA-PHB blend films, percolating networks of single-walled carbon nanotubes (SWCNTs) having sheet resistance well below 1 kΩ/□ can be deposited by dip coating to make electrode plates of capacitive touch sensors. We also demonstrate that the bioplastic films, as flexible dielectric substrates, are suitable for depositing conductive micropatterns of SWCNTs and Ag (1 kΩ/□ and 1 Ω/□, respectively) by means of inkjet and screen printing, with potential in printed circuit board applications. In addition, we exemplify compounded and molded composites of PLA with PL and MWCNTs as excellent candidates for electromagnetic interference shielding materials in the K-band radio frequencies (18.0-26.5 GHz) with shielding effectiveness of up to 40 and 46 dB, respectively.

M(II)Al4 Type Layered Double Hydroxides-Preparation Using Mechanochemical Route, Structural Characterization and Catalytic Application.

The synthesis of the copper-poor and aluminum-rich layered double hydroxides (LDHs) of the CuAl4 type was optimized in detail in this work, by applying an intense mechanochemical treatment to activate the gibbsite starting reagent. The phase-pure forms of these LDHs were prepared for the first time; using copper nitrate and perchlorate salts during the syntheses turned out to be the key to avoiding the formation of copper hydroxide sideproducts. Based on the use of the optimized syntheses parameters, the preparation of layered triple and multiple hydroxides was also attempted using Ni(II), Co(II), Zn(II) and even Mg(II) ions. These studies let us identify the relative positions of the incorporating cations in the well-known selectivity series as Ni2+ >> Cu2+ >> Zn2+ > Co2+ >> Mg2+. The solids formed were characterized by using powder X-ray diffractometry, UV-Vis diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The catalytic potential of the samples was investigated in carbon monoxide oxidation reactions at atmospheric pressure, supported by an in situ diffuse reflectance infrared spectroscopy probe. All solids proved to be active and the combination of the nickel and cobalt incorporation (which resulted in a NiCoAl8 layered triple hydroxide) brought outstanding benefits regarding low-temperature oxidation and increased carbon monoxide conversion values.

One-pot mechanochemical ball milling synthesis of the MnOx nanostructures as efficient catalysts for CO2 hydrogenation reactions.

Here, we report on a one-pot mechanochemical ball milling synthesis of manganese oxide nanostructures synthesized at different milling speeds. The as-synthesized pure oxides and metal (Pt and Cu) doped oxides were tested in the hydrogenation of CO2 in the gas phase. Our study demonstrates the successful synthesis of the manganese oxide nanoparticles via mechano-chemical synthesis. We discovered that the milling speed could tune the crystal structure and the oxidation state of the manganese, which plays an essential role in the CO2 hydrogenation evidenced by ex situ XRD and XPS studies. The pure MnOx milled at 600 rpm showed high catalytic activity (∼20 000 nmol g-1 s-1) at 823 K, which can be attributed to the presence of Mn(ii) besides Mn(iii) and Mn(iv) on the surface under the reaction conditions. This study illustrates that the milling method is a cost-effective, simple way for the production of both pure, Pt-doped and Cu-loaded manganese nanocatalysts for heterogeneous catalytic reactions. Thus, we studied the Pt incorporation effect for the catalytic activity of MnOx using different Pt loading methods such as one-pot milling, wet impregnation and size-controlled 5 nm Pt loading via an ultrasonication-assisted method.

Biosynthesis of silver nanoparticle using extract of Zea mays (corn flour) and investigation of its cytotoxicity effect and radical scavenging potential.

Silver nanoparticles (AgNPs) possesses a number of exceptional pharmaceutical properties and applications as compared with other types of metallic nanoparticles. Currently, AgNPs was biosynthesized using an aqueous extract of Zea mays L. (corn flour) powder. Further, the effect of concentration of reagents, extract, temperature and time of synthesis was also studied along with the cytotoxicity and radical scavenging potential. UV-vis spectra of AgNPs gave a surface plasmon resonance at ~420 nm. The absorption peak became sharp with the increase in time. AgNPs with monodispersed and aggregated spherical shape was observed by SEM image followed by its confirmation via strong signal in silver region of EDX spectrum. The XRD spectra confirmed its crystallinity and face-centered cubic structure. FT-IR spectra reveal the presence of phytocompounds in the synthesis of AgNPs. Further, the AgNPs exhibited strong cytotoxicity potential against HepG2 cells and its viability declined with an increase in the concentration of AgNP with respect to the control cells. It also demonstrated reasonable radical scavenging potential in terms of DPPH and ABTS scavenging, and reducing power tests. Taken together, these results of the current investigation stated that AgNPs could be beneficial in biomedical applications particularly for treatment of cancer disease along with its applications in pharmaceutical industries for the formulation of new drugs.

Designed Pt Promoted 3D Mesoporous Co3O4 Catalyst in CO2 Hydrogenation.

Controlled size Pt nanoparticles were anchored onto the surface of 3D mesoporous cobalt-oxide support and was tested in CO2 hydrogenation reactions compared to commercial cobalt-oxide supported Pt nanoparticles prepared by the wet impregnation method as well as SBA-15 silica supported nanoparticles. Designed Pt/mesoporous cobalt-oxide catalysts showed the highest activity as well as the highest methane selectivity. Such catalyst was active at 573 K, while other catalysts showed activity >673 K.

Size-Dependent H2 Sensing Over Supported Pt Nanoparticles.

Catalyst size affects the overall kinetics and mechanism of almost all heterogeneous chemical reactions. Since the functional sensing materials in resistive chemical sensors are practically the very same nanomaterials as the catalysts in heterogeneous chemistry, a plausible question arises: Is there any effect of the catalyst size on the sensor properties? Our study attempts to give an insight into the problem by analyzing the response and sensitivity of resistive H2 sensors based on WO3 nanowire supported Pt nanoparticles having size of 1.5±0.4 nm, 6.2±0.8 nm, 3.7±0.5 nm and 8.3±1.3 nm. The results show that Pt nanoparticles of larger size are more active in H2 sensing than their smaller counterparts and indicate that the detection mechanism is more complex than just considering the number of surface atoms of the catalyst.

Outstanding Activity and Selectivity of Controlled Size Pt Nanoparticles Over WO3 Nanowires in Ethanol Decomposition Reaction.

Pt nanoparticles with controlled size of 1.5 and 6.5 nm were anchored onto the surface of WO3 nanowires (WO3NW) as well as on MCF-17 silica. In the case of WO3NW and MCF-17 supported nanoparticles, 1.5 nm Pt nanoparticles were more active in ethanol decomposition reaction at 533 K. 6.5 nm Pt/WO3NW catalyst showed ~6 times higher activity compared to MCF-17 supported 6.5 nm Pt nanoparticles. While MCF-17 supported catalysts produced hydrogen, methane, carbon-monoxide and acetaldehyde, the tungsten-oxide supported Pt nanoparticles produced a huge amount of acetone as well as ethene with a high acetaldehyde selectivity besides H2, CH4 and CO. The hydrogen formation was significantly higher when the Pt size was 1.5 nm. The metallic nanoparticles, the acid sites and the oxidized centers of support play important role in the formation of decomposition products of ethanol.

Effect of Particle Restructuring During Reduction Processes Over Polydopamine-Supported Pd Nanoparticles.

The effect of catalyst restructuring on the polydopamine-supported Pd catalyzed transfer hydrogenation of ethyl 4-nitrobenzoate and the catalytic hydrogenation of (E)-2-methyl-2-butenoic acid is reported. Transmission electron microscopy investigation of different catalyst pre-treatment and reaction conditions revealed high catalytic activity in both reactions unless drastic aggregation of the active metal occurred. In the transfer hydrogenation reaction aggregation was primarily dependent on the H-source used, while in the catalytic hydrogenation additives in combination with the reductive environment led to extensive Pd aggregation and thus decreased catalytic activity. The enantioselective hydrogenation of (E)-2-methyl-2-butenoic acid showed increased enantioselectivity and decreased conversion with increased particle size.

In situ growth of graphdiyne on arbitrary substrates with a controlled-release method.

A versatile controlled-release method was developed for the in situ growth of graphdiyne on arbitrary substrates. Cu2+-Ions escaped from the polyvinylpyrrolidone/copper acetate film on the surface of various substrates (e.g. SiO2, ZnO, Al, etc.), acting as the catalyst for the acetylenic coupling reaction.

Photoelectrochemistry by Design: Tailoring the Nanoscale Structure of Pt/NiO Composites Leads to Enhanced Photoelectrochemical Hydrogen Evolution Performance.

Photoelectrochemical hydrogen evolution is a promising avenue to store the energy of sunlight in the form of chemical bonds. The recent rapid development of new synthetic approaches enables the nanoscale engineering of semiconductor photoelectrodes, thus tailoring their physicochemical properties toward efficient H2 formation. In this work, we carried out the parallel optimization of the morphological features of the semiconductor light absorber (NiO) and the cocatalyst (Pt). While nanoporous NiO films were obtained by electrochemical anodization, the monodisperse Pt nanoparticles were synthesized using wet chemical methods. The Pt/NiO nanocomposites were characterized by XRD, XPS, SEM, ED, TEM, cyclic voltammetry, photovoltammetry, EIS, etc. The relative enhancement of the photocurrent was demonstrated as a function of the nanoparticle size and loading. For mass-specific surface activity the smallest nanoparticles (2.0 and 4.8 nm) showed the best performance. After deconvoluting the trivial geometrical effects (stemming from the variation of Pt particle size and thus the electroactive surface area), however, the intermediate particle sizes (4.8 and 7.2 nm) were found to be optimal. Under optimized conditions, a 20-fold increase in the photocurrent (and thus the H2 evolution rates) was observed for the nanostructured Pt/NiO composite, compared to the benchmark nanoparticulate NiO film.