Deep eutectic solvents (DES) have emerged as promising solutions in many areas of chemistry. DES have many of the advantages of ionic liquids (e.g., low vapor pressure, nonflammability, tunability, etc.) but have lower costs, straightforward syntheses, and are often biodegradable. In this minireview, we discuss briefly the applications of DES in areas such as biotransformations, organocatalysis, and combinations of these that lead to multistep processes. DES can be used as solvents, cosolvents, performance additives for bio‐ and organocatalysis, tools to anchor organocatalysts selectively, or for extraction/separation. Several DES have been used both as solvents and organocatalysts at the same time. Given their promising features, it may be expected that many applications in these areas will appear in the coming years.

The use of deep eutectic solvent (DES)/water mixtures were explored for the selective enzymatic synthesis of α‐monobenzoate glycerol (α‐MBG) from glycerol and benzoic acid as substrates. Experiments were performed with four DES, three of them containing choline chloride (ChCl), combined with urea (URA), glycerol (GLY), and ethylene glycol (ETA) (in all cases ChCl/HBD 1:2 mol ratio), and another one formed with methylammonium chloride and glycerol (MA/GLY 1:3 mol ratio). The best conversions (99 %) were achieved with immobilized lipase B from Candida antarctica (CAL‐B) when ChCl/GLY was used as the solvent and the substrate at the same time. The use of water as a cosolvent (8 % v/v) led to a significant decrease in the viscosity of the DES, and full conversions were then reached. Reusability studies of the biocatalyst revealed a 37 % decrease in activity after the first batch, but the activity remained mostly constant for the rest of the cycles.

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Hematite nanostructures were electrochemically grown by ultrasound-assisted anodization of iron substrates in an ethylene glycol based medium. These hematite nano-architectures can be tuned from a 1-D nanoporous layer to a self-organized nanotube one if the grown is done onto a bare iron foil substrate or onto an electrochemical pretreated one, respectively. Depending upon the pre-treatment conditioning, the self-organized nanotube layer consists of nanotube arrays with a single tube inner diameter of approximately 40-50 nm and wall thickness of 20-30 nm. Their morphological, structural and optoelectronic properties are studied. The photoelectrochemical properties of the resulting hematite nanostructures are studied from the point of view of their application as photoanodes in splitting of water. Through the photocurrent transients for the three nanostructured hematite type electrodes under study, the rate constants k tr and k rec corresponding to the rate constant of charge transfer and recombination processes have been determined. In all cases, the potential value where k tr > k rec was attained at more negative values than the reversible potential of water oxidation, indicating a photocatalytic effect. All samples show a maximum IPCE value between 350 and 375 nm, being the samples pretreated at −1.0 V which shows the highest IPCE value: 45% at 375 nm. In the last years, hydrogen energy has found increased attention as a renewable and clean energy source.1-5 Among many methods, solar hydrogen generation by photoelectrochemical (PEC) water splitting is a particularly attractive one because of the environmental friendless and the abundance of water and solar energy without emission of pollutants. [1][2][3][4][5] Since 1972, when the pioneering work on PEC water splitting was reported by Fujishima and Honda, 6 a wide range of materials has been investigated. In fact, semiconductor materials such as TiO 2 , SrTiO 3 , WO 3 , ZnO, BiVO 4 and Cu(In,Ga)Se 2,3,4,[7][8][9][10] have been used for the development of photoanodes in PEC cells.Compared to these materials, α-Fe 2 O 3 (hematite), has a narrower band-gap (1.9-2.2 eV), which allows to harvest up to 40% of the incident solar radiation. Furthermore, α-Fe 2 O 3 is a promising semiconducting material for photoelectrochemical and photocatalysis applications due to its stability, abundance and environmental compatibility, as well as convenient position of the valence band. 3,[11][12][13][14][15][16][17][18][19][20][21][22][23] In spite of the good properties presented by the α-Fe 2 O 3 , several problems must be solved in order to convert this material in an optimal one for certain applications. For instance, two of these problems correspond to: i) the very short hole diffusion length (20 nm, 24 2-4 nm) 25 compared to the light penetration depth (α −1 = 118 nm at λ = 550 nm), which results in the rapid non-radiative electron-hole recombination inside the semiconductor, and ii) poor electrical conductivity. [26][27][28] Two approaches have been taken to tackle the shor...

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