Partial oxidation of furanic biomass derivatives such as furfural is of interest for the sustainable production of chemicals including furoic acid, maleic acid, and 2,5-furandicarboxylic acid (FDCA). The oxidative bulk electrolysis of furfural is here investigated on platinum electrodes in acidic media. The effects of potential, concentration, pH, and supporting anion are studied, and selectivity trends are coupled with attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) to illuminate adsorbate structures that influence the catalysis. Increasing potential is found to shift selectivity from primarily C5 products to C4 products, coincident with oxidation of the Pt surface. Selectivity changes are also observed moving from pH 1 to pH 4, with an increase in C5 products at higher pH. Changing from the weakly adsorbing perchlorate anion to the specifically-adsorbing phosphate anion results in a number of changes that manifest differently depending on potential and pH. Selectivity to furoic acid is found to be highest above the pKa of phosphoric acid due to the strongly adsorbed phosphate ions suppressing flat-lying configurations of furfural that lead to C-C cleavage. These results point toward opportunities to use electrolyte engineering to tune selectivity and optimize surface conditions to disfavor binding of inhibitory products.
Platinum‐DNA Origami Hybrid Structures in Concentrated Hydrogen Peroxide
DNA origami nanostructures are surprisingly stable in up to 5 % hydrogen peroxide over the course of three days and can thus be rendered catalytically active through efficient and reliable coupling to platinum nanoparticles.
Abstract
The DNA origami technique allows fast and large-scale production of DNA nanostructures that stand out with an accurate addressability of their anchor points. This enables the precise organization of guest molecules on the surfaces and results in diverse functionalities. However, the compatibility of DNA origami structures with catalytically active matter, a promising pathway to realize autonomous DNA machines, has so far been tested only in the context of bio-enzymatic activity, but not in chemically harsh reaction conditions. The latter are often required for catalytic processes involving high-energy fuels. Here, we provide proof-of-concept data showing that DNA origami structures are stable in 5 % hydrogen peroxide solutions over the course of at least three days. We report a protocol to couple these to platinum nanoparticles and show catalytic activity of the hybrid structures. We suggest that the presented hybrid structures are suitable to realize catalytic nanomachines combined with precisely engineered DNA nanostructures.
Dynamic Structural Evolution of CeO2 in CuO−CeO2 Catalyst Revealed by In Situ Spectroscopy
The structural evolution of CeO2 in CeO2−CuO catalyst was captured by in situ technique. Under reductive conditions, CeO2 was exposed to the catalyst surface to form an inverse CeOx/Cu interface with a high WGS activity. After the removing of the reductive condition, CeO2 in the catalyst will undergo a surface reconstruction, which is manifested as oxygen migration and oxidation of Cu.
Abstract
The oxides and active metals at the interface synergistically activate reactants and thus promote the reaction, but the interface structure often changes dynamically during the reaction. In the conventional supported catalysts, the metals at the interface have been extensively studied, while the structural evolution of oxides is often overlooked due to the interference of the bulk phase signal. In this work, CeO2−CuO inverse catalysts are designed to reveal the dynamic structure evolution of CeO2 in the CeO2−CuO system during the water gas shift (WGS) reaction by in situ Raman, in situ XRD, quasi in situ XPS, and near ambient pressure XPS (NAP-XPS). CeO2 is partially concealed in the CuO phase in the un-pretreated catalyst and gradually exposed to the surface, forming an inverse CeO x /Cu structure during the reducing process. This structure exhibits a high catalytic activity in the WGS reaction and remains durable under the reductive conditions. When the inverse CeO x /Cu structure is exposed to the non-redox conditions, the reconfiguration of the reduced oxide is observed which is caused by the oxygen migration of CeO2. This work explores the structure evolution of CeO2 in CeO2−CuO inverse catalyst under different conditions by in situ characterization technique and provides a reference for monitoring the dynamic changes of oxide structure.
Preparation and Characterization of Hollow CeO2 Nanoparticles for the Efficient Conversion of CO2 into Dimethyl Carbonate
Hollow CeO2 nanoparticles mesoporous defects were prepared by a solid template method, and showed good catalytic performance for the conversion of CO2 into DMC owing to its abundant mesoporous defects and high oxygen vacancy concentration.
Abstract
The hollow CeO2 (H-CeO2) nanoparticles with mesoporous defects structure were prepared by a solid template method under ambient pressure and applied to catalyze the conversion of CO2 into dimethyl carbonate (DMC). The textural properties of H-CeO2 were investigated by various characterization techniques. The results showed that H-CeO2 have higher surface area, more mesoporous defects and higher surface oxygen vacancies concentration than those of conventional CeO2 with block morphology (C-CeO2). Therefore, H-CeO2 exhibited better catalytic performance for the conversion of CO2 into DMC. Additionally, the Ce(NO3)3 ⋅ 6H2O amount in preparation procedure was important for the formation of hollow structure and mesoporous defects. The DMC yield could reach 4.96 % on H-CeO2-1.2 (Ce(NO3)3 ⋅ 6H2O amount: 1.2 g) catalyst when the reaction was performed at 140 °C and 4.5 MPa for 4 h. This work proposed a facile strategy for designing CeO2 catalysts for the CO2 conversion by creating mesoporous defective structure.
CO2 Hydrogenation to CH3OH over Cu‐Based Catalysts: Primary and Side Reactions
This review systematically analyses recent studies on CO2 hydrogenation to methanol with a focus put on primary and secondary reactions. Thermodynamic aspects, active sites and reaction mechanisms are discussed. We also provide personal views on possible developments in this area and recommendations for catalytic tests and their evaluation to properly compare different catalysts.
Abstract
Carbon dioxide (CO2) hydrogenation to methanol (CH3OH) is one of the most promising approaches to provide this platform chemical and to close carbon cycles. In this minireview, we systematically analyze primary and secondary reactions which can take place in this reaction over Cu-based catalysts. In addition to repeatedly discussed reverse water gas shift reaction (RWGS) and CH3OH production directly from CO2, we consider decomposition, dehydration, dehydrogenation, and steam reforming of the desired alcohol. These reactions are usually ignored in the studies dealing with CO2 hydrogenation to CH3OH but can worsen the catalyst efficiency. Apart from the corresponding thermodynamic analysis, proposed reaction mechanisms and active sites are described and discussed. The effects of co-fed water, CH3OH and methyl formate on catalyst performance are critically scrutinized, too. We also provide several criteria for unambiguous comparison of different catalysts in terms of CH3OH selectivity and their activity.
Catalysts Originating from Tailor‐made Metal Ethylene Glycol Carboxylates
Ethylene glycol metal carboxylates are excellent catalyst precursors for heterogeneous reactions, or can directly be applied in homogeneous catalysis. Applications beyond catalysis are presented.
Abstract
Ethylene glycol metal carboxylates are suited as low-temperature precursors for M and MxOy nanoparticle formation, which are applicable in catalytic heterogeneous reactions including hydrogenations, hydrometalations or C,C cross-couplings. For the synthesis of β-oxo-propyl and enol esters [Ru(CO)2(PPh3)2(O2CR)2] complexes are excellent homogeneous catalysts with high regioselectivities. Additionally, applications of the title complexes beyond catalysis are presented.
Analysis of Dynamical Peculiarities in Nanoalloys at Subsystems Level: Dynamical Degrees of Freedom, Temperature Differences, and the Chameleon Effect
Vibrational temperatures of pure and mixed 13-atom Ni/Al clusters as a function of the cluster composition and internal energy.
Abstract
A novel analysis of the dynamical behavior of nanoalloy systems, as represented by model Ni/Al 13-atom clusters, over a broad range of energies that cover the stage-wise transition of the systems from their solid-like to liquid-like state is presented. Conceptually, the analysis is rooted in partitioning the systems into judiciously chosen subsystems and characterizing the latter in terms of subsystem-specific dynamical descriptors that include dynamical degrees of freedom, root-mean-square bond-length fluctuation, and element-specific subsystem temperature. The analysis reveals a host of intriguing new peculiarities in the dynamical behavior of the Ni/Al 13-mers, among which are what we call the chameleon effect and the difference in the temperatures of the Ni and Al subsystems at high energies, a difference that strongly depends on the cluster composition and also changes with energy. These do not have an analog in pure Ni13 and Al13 and are explained in terms of the coupled effects of the difference between the masses of the Ni and Al atoms (the mass effect) and of the difference in the anharmonicity of the overall interaction potential as experienced by the Ni and Al subsystems of the clusters (the potential effect).
Conformal Coverage of ZnO Nanowire Arrays by ZnMnO3: Room‐temperature Photodeposition from Aqueous Solution
Crystalline–amorphous biphasic ZnMnO3 was photodeposited by a one-step, room-temperature process from an aqueous precursor solution onto ZnO nanowires. The specific morphology of the photodeposit and its homogeneous dispersion at the nanowire surface give rise to an electrode architecture, where ZnMnO3 shells act as an electroactive, pseudocapacitive phase in aqueous electrolytes.
Abstract
Compositionally and structurally complex semiconductor oxide nanostructures gain importance in many energy-related applications. Simple and robust synthesis routes ideally complying with the principles of modern green chemistry are therefore urgently needed. Here we report on the one-step, room-temperature synthesis of a crystalline–amorphous biphasic ternary metal oxide at the ZnO surface using aqueous precursor solutions. More specifically, conformal and porous ZnMnO3 shells are photodeposited from KMnO4 solution onto immobilized ZnO nanowires acting not only as the substrate but also as the Zn precursor. This water-based, low temperature process yields ZnMnO3/ZnO composite electrodes featuring in 1 M Na2SO4 aqueous solution capacitance values of 80–160 F g−1 (as referred to the total mass of the porous film i. e. the electroactive ZnMnO3 phase and the ZnO nanowire array). Our results highlight the suitability of photodeposition as a simple and green route towards complex functional materials.
Efficient Palladium Catalysts: Application and Challenges of Electrocatalytic Hydrodechlorination Technology in Wastewater Treatment
This review summarizes the application of palladium catalysts in electrocatalytic hydrodechlorination for the removal of chlorinated organic pollutants. Some strategies for modulating palladium to enhance activity are discussed and future developments in the field are outlined.
Abstract
This review summarizes the research progress of palladium (Pd) catalysts in electrocatalytic hydrodechlorination (ECH) for the removal of chlorinated organic pollutants (COPs). ECH technology is a new type of green water treatment technology without secondary pollution, which has excellent removal effect on COPs. Pd is widely used in the field of ECH due to its excellent catalytic properties. However, the easy deactivation and high price of Pd have limited the application of Pd catalysts in practical wastewater treatment. Researchers have improved the performance of Pd catalysts for ECH by improving the morphological structure (dispersion, particle size, crystalline surface) and electronic states (electron-rich Pd, electron-deficient Pd). It is also found that modulation of the adsorption abilities of Pd catalysts can greatly improve the catalytic activity. The factors affecting the stability of Pd catalysts are also investigated, and the future large-scale mature application of ECH technology is envisioned. The ability to prepare single-atom Pd catalysts in a relatively simple way is a future direction, which will achieve 100 % atom utilization and thus significantly reduce the cost of Pd. This review details the frontier research on Pd catalysts in the field of ECH, which can provide some good strategies for related researchers.
Screening Campaign and Docking Investigations in Identifying New Hit Compounds as Inhibitors of Human Carbonic Anhydrases Expressed In Tumour Cells
We explored our in-house collection of sulfonamides to identify new potent hCA IX/XII inhibitors. Docking simulations highlighted the docking poses in catalytic sites of hCA IX and hCA XII cavities. These structural findings may help lead to the successful identification of new sulfonamides as adjuvant agents in cancer management.
Abstract
The tumor-expressed human carbonic anhydrase (hCA) isoforms hCA IX and hCA XII have been extensively studied to develop anticancer agents targeting solid tumors in combined therapy. These CA isoforms are considered key factors in controlling tumor microenvironment (TME) of cancer lines that develop high metastatic activity. Herein, we report the discovery of potent hCA IX/hCA XII inhibitors that were disclosed through a screening campaign on an in-house collection of arylsulfonamides preliminary tested toward other hCAs. Among them, the N-(4-sulfamoylphenyl)naphthalene-2-carboxamide (12) and N-(4-sulfamoylphenyl)-3,4-dihydroisoquinoline-2(1H)-carbothioamide (15) proved to be the most intriguing hCA IX/hCA XII inhibitors displaying favourable selectivity ratios over widespread hCA I and hCA II isoforms. To explore their binding mode, we conducted docking studies that described the poses of the best inhibitors in the catalytic site of hCA IX and hCA XII, thus suggesting the privileged pattern of interactions. These structural findings might further improve the knowledge for a successful identification of new sulfonamides as adjuvant agents in cancer management.