ChemSusChem

The cover image highlights the research carried out by the group of Francesco Vizza at ICCOM-CNR in Florence, which is reported on page 518. It shows a direct alcohol fuel cell (DAFC) that converts alcohols into various oxygenate products, providing at the same time excellent power densities, thus exploiting the ability of the anode electrocatalyst to bring about the partial oxidation of either ethylene glycol (EG) or glycerol (G) with high selectivity and fast kinetics. The power densities obtained in the temperature range from 20 to 80 °C, with palladium loadings at the anode as low as 1 mg cm⁻², show that Pd-(Ni-Zn)/C can be classified as the best performing palladium-based electrocatalyst ever reported for EG and G electro-oxidation.

“Processes that selectively produce industrially relevant feedstocks from renewables with concomitant release of energy can be realized for alcohols such as glycerol and ethylene glycol by means of devices such as direct alcohol fuel cells (DAFCs).” This and more about the story behind the front cover research can be found on p. 390.

Getting phases together: Membrane microreactors provide new opportunities for gas–liquid reactions. The advantages of this microreactor concept are a large interfacial area, a greater flexibility with regard to flow rates, and the opportunity to immobilize a catalyst on the membrane.

Wearable power supplies: Photo-rechargeable devices integrating power conversion and energy storage functions are useful for supplying power to portable electronics. A recent report introduces a facile method to fabricate flexible dual-functional devices on a single metal wire which paves the way for wearable fabric power supplies.

Ta-based compounds show Pt-like behavior: Binary tantalum compounds as counter electrodes (CEs) in dye-sensitized solar cells (DSCs) demonstrate Pt-like electrocatalytic activity and competitive photovoltaic performance, matching the performance of DSCs with Pt CEs. The first-principle density functional theory (DFT) calculations provide a strategy for understanding the relationship between the electronic structure and the catalytic activity of CE catalysts in DSCs.

Forget about CO! Carbonylations are among the most important homogeneously catalyzed reactions in the chemical industry, but typically require carbon monoxide. Instead, straightforward and efficient alkoxycarbonylations of olefins can proceed with alkyl formates in the presence of a specific palladium catalyst. Aromatic, terminal aliphatic, and internal olefins are carbonylated to give industrially important linear esters at low catalyst loadings.

Last site standing: A new generation of hierarchical Pt/H-ZSM-22 zeolites is designed for the efficient processing of upcoming renewable feedstocks. The enhanced accessibility of the active sites is vital for the superior activity and exceptional selectivity in the hydroisomerization of model molecules such as nonadecane and pristane.

Transmission of alcohols achieved: A method for the direct transfer of the CHOH function from simple polyols to alkenes has been developed. In a dual-reactor system, successive iridium-catalyzed dehydrogenations and decarbonylations of polyols such as glycerol and sorbitol generates a low pressure of syngas, which is directly used in ex situ alkene hydroformylation.

Terminal aromatic alkynes are converted rapidly into ketones in a regioselective manner by treatment of their microemulsions with 0.33 M mineral acid between 80 and 140 °C. Internal and aliphatic acetylenes are likewise hydrated, but require longer reaction periods. The products are easily isolated from the reaction mixtures by phase separation. Replacement of H₂O by D₂O leads to the formation of trideuteriomethyl ketones.

Playing your part: Conductive magnetite nanoparticles accelerate the microbial reductive dechlorination of trichloroethene (TCE), an ubiquitous and toxic subsurface contaminant. The stimulatory effect most likely results from the nanoparticles promoting the establishment of interspecies electron transfer (IET) processes between non-dechlorinating and dechlorinating microorganisms.

Water repulsion and CO₂ attraction: We have developed a SiO₂ aerogel membrane modified with CF₃ functional groups. This has the potential to be used in a membrane contactor for CO₂ absorption. The as-coated hydrophobic SiO₂ aerogel membranes reveal excellent reusability. The hydrophobized silica aerogel membrane contactor is a promising technology for large-scale CO₂ absorption during the post-combustion process in power plants.

Blend and conquer: A blended electrolyte that consists of propylene carbonate and an ionic liquid is tested for Li–O₂ batteries. Both components perform complementary functions to each other to overcome the drawbacks of the other component. Such synergistic effects allow substantially improved lifetimes, the most critical parameter in Li–O₂ batteries. This study confirms the importance and opportunities of the use of electrolytes in Li–O₂ batteries.

Electron collection: A high-potential material, BaSnO₃, as the photoanode of a dye-sensitized solar cell (DSSC) is explored. The DSSC that is fabricated using highly crystalline BaSnO₃ nanoparticles shows an overall energy conversion efficiency of 5.2 %, which is the highest performance in ternary oxide-based DSSCs. This high performance comes from rapid charge capture in the BaSnO₃ nanoparticle photoelectrode.

Electrocatalytic glucose hydrogenation: The hydrogenation of glucose to sorbitol or 2-deoxysorbitol in neutral media has been studied on solid metal electrodes. Three groups of catalysts can be identified from the periodic table, with regard to the main reaction products: (1) early transition metals and platinum group metals (hydrogen formation); (2) late transition metals and Al (sorbitol formation); and (3) post-transition metals, as well as Zn, and Cd (sorbitol and 2-deoxysorbitol formation).

Carbon supports improve catalytic activity: The yield of the catalytic acetone–furfural aldol condensation is improved by supporting the Mg–Zr mixed oxide on carbon nanofibers and high surface area graphites. For preparation of the catalysts, coprecipitation achieves the best conversion and selectivity towards C₁₃ compounds (biodiesel precursor). This behavior is consistent with improved basic site distribution and increased interaction of the reactants with the carbon surface.

The energy superstore: High performance supercapacitor electrodes based on MnO₂–CNT–graphene oxide nanocomposites are fabricated using graphene oxide as a surfactant to directly disperse pristine carbon nanotubes. Subsequently, MnO₂ nanorods have been deposited to produce a supercapacitor electrode that exhibits ideal capacitive behavior in addition to many other advantageous characterisitics.

Composition influences sintering and performance: The performance of selenized Cu(In,Ga)Se₂ nanocrystal photovoltaics has been observed to change dramatically with different [Ga]/[In+Ga] ratios in the nanocrystals. The [Ga]/[In+Ga] concentration alters the [Cu]/[In+Ga] content in the nanocrystals, which influences sintering and film morphology (see image), leading to very significant variations in device efficiency.

Speed dating for electrons: Heterogeneous electron transfer across the biofilm/electrode interface is a slow process promoted by surface-confined cytochromes that are not in direct physical contact with the electrode. Subsequent electron transfer from the surface-confined cytochromes to more remote redox centers within the biofilm is a much faster process. Herein, an approach is identified as a powerful tool for selectively probing interfacial processes of biofilms close to the electrode surface.

Double doping: S and N co-doped, few-layered graphene oxide catalysts show increased activity for the electroreduction of oxygen compared to mono-doped S and N carbon nanomaterials. The co-doped catalysts exhibit competitive catalytic activity (10 mA cm⁻² kinetically limited current density at −0.25 V versus Ag/AgCl) and superior methanol tolerance and durability in comparison to the commercial Pt/C catalyst.

Support for platinum: The hydrothermal treatment of cellulose under H₂ in the presence of tungstated alumina-based catalysts (AlW) yields lactic acid or acetol and propylene glycol as the main products depending on the presence or absence of supported platinum.

Pushing and pulling: A push–pull porphyrin with an electron-donating and an electron-withdrawing group at opposite sites has been synthesized to evaluate the effect of the push–pull structure on optical, electrochemical, and photovoltaic properties. This system exhibited a power conversion efficiency that is higher than that of the dye without the electron-donating group.

An excellent electrocatalyst! The electrooxidation of ethylene glycol (EG) and glycerol (G) has been studied, in alkaline media, in passive as well as active direct ethylene glycol fuel cells and direct glycerol fuel cells containing Pd-(Ni-Zn)/C as anode electrocatalyst, that is, Pd nanoparticles supported on a Ni–Zn phase. Pd-(Ni-Zn)/C can be classified amongst the best performing Pd-based electrocatalysts ever reported for EG and G oxidation.

Value-added waste: A new lignin valorization approach is proposed that involves ultrafiltration as a fractionation process to separate different molecular weight (MW) lignin fractions followed by a hydrogen-free, mild, hydrogenolytic, heterogeneously catalyzed methodology (see picture; NP=nanoparticle).

Chitin aerogels are prepared by the aqueous self-assembly of chitin nanowhiskers under low-power sonication, followed by solvent exchange with ethanol and drying with scCO₂. The aerogels have a high modulus and only shrink by 4 % on average during the solvent exchange and scCO₂ drying steps. These aerogels could be useful as thermal insulators, catalyst supports and for the construction of biomedical materials.