MoS2 is a promising and low-cost material for electrochemical hydrogen production due to its high activity and stability during the reaction. However, the efficiency of hydrogen production is limited by the amount of active sites, for example, edges, in MoS2. Here, we demonstrate that oxygen plasma exposure and hydrogen treatment on pristine monolayer MoS2 could introduce more active sites via the formation of defects within the monolayer, leading to a high density of exposed edges and a significant improvement of the hydrogen evolution activity. These as-fabricated defects are characterized at the scale from macroscopic continuum to discrete atoms. Our work represents a facile method to increase the hydrogen production in electrochemical reaction of MoS2 via defect engineering, and helps to understand the catalytic properties of MoS2.

We examine a large number of DFT calculations regarding the chemistry of oxide surfaces and show that their qualitative conclusions can be predicted by using a few rules derived from the Lewis acid−base properties of the species involved. (1) The presence of a Lewis acid on an oxide surface increases substantially the binding energy of a Lewis base. ( 2) If an oxide has certain properties because it is a Lewis base, these properties can be suppressed by adsorbing a Lewis acid on the surface. (3) The presence of a Lewis base on an oxide surface diminishes the binding energy of another base, as compared to the binding energy on the same surface with no base on it. These rules also hold if the words "acid" and "base" are exchanged. We show that these rules apply to a large number of systems which seem to have no relationship to each other and which are important for catalysis by oxides.

Lithium–sulfur (Li–S) batteries are strongly considered for next-generation energy storage devices. However, severe issues such as the shuttle of polysulfides restrict their practical applications. Exploring the design principle of anchoring polysulfides physically and chemically through the polar substrate is therefore highly necessary. In this Letter, first-row transition-metal sulfides (TMSs) are selected as the model system to obtain a general principle for the rational design of a sulfur cathode. The strong S-binding that is induced by charge transfer between transition-metal atoms in TMS slabs and S atoms in Li2S is confirmed to be of great significance in TMS composite cathodes. An analogous periodic law is proposed, which is also extended to first-row TM oxides. VS has the strongest anchoring effects on Li2S immobilization and a relatively low lithium ion diffusion barrier. The binding energies and Li diffusion properties are considered as the key descriptors for the rational design of sulfur cathodes.

Lightweight, stretchable, and wearable strain sensors have recently been widely studied for the development of health monitoring systems, human-machine interfaces, and wearable devices. Herein, highly stretchable polymer elastomer-wrapped carbon nanocomposite piezoresistive core-sheath fibers are successfully prepared using a facile and scalable one-step coaxial wet-spinning assembly approach. The carbon nanotube-polymeric composite core of the stretchable fiber is surrounded by an insulating sheath, similar to conventional cables, and shows excellent electrical conductivity with a low percolation threshold (0.74 vol %). The core-sheath elastic fibers are used as wearable strain sensors, exhibiting ultra-high stretchability (above 300%), excellent stability (>10 000 cycles), fast response, low hysteresis, and good washability. Furthermore, the piezoresistive core-sheath fiber possesses bending-insensitiveness and negligible torsion-sensitive properties, and the strain sensing performance of piezoresistive fibers maintains a high degree of stability under harsh conditions. On the basis of this high level of performance, the fiber-shaped strain sensor can accurately detect both subtle and large-scale human movements by embedding it in gloves and garments or by directly attaching it to the skin. The current results indicate that the proposed stretchable strain sensor has many potential applications in health monitoring, human-machine interfaces, soft robotics, and wearable electronics.

CORRIGENDUM The editorial team of ChemCatChem would like to correct mistakes in Schemes 1 and 2. In Scheme 1, the most important change is that there should be no carbon-carbon double bond in levulinic acid. In Scheme 2 there are two mistakes concerning the structure of molecules (g-valerolactone and 4-hydroxypentanoic acid), and the transformation from 4-hydroxypentanoic acid to g-valerolactone should proceed through dehydration not through reduction. Please see the corrected schemes below. The authors and the editors of ChemCatChem apologize for this oversight.

We use density functional theory to study the chemistry of oxides doped substitutionally with cations having lower valence than that of the host. We document two rules. (1) The presence of the dopant makes the oxide a better oxidant. (2) Adsorbing an electron donor on the surface counteracts strongly the effect of the dopant. We discuss how these rules affect methane activation by doped-oxide catalysts.

La2O3 is one of the more efficient oxide catalysts for oxidative methane coupling. In this article, we examine the extent to which methane activation can be improved by replacing a La cation in the surface layer with other cations. The purpose of these substitutional dopants is to make the oxygen atoms in their neighborhood more reactive, which makes the doped oxide a better oxidant. We examined doping the surface layer of La2O3(001) and (011) with Cu, Zn, Mg, Fe, and Al. We have chosen dopants whose oxide formation enthalpy is less than that of La2O3. Some (Cu, Fe) are capable of having two different valence states, whereas some (Zn, Mg, Al) have only one. All of them lower substantially the energy of vacancy formation on the two faces. We use a “moderation principle” to suggest that Cu-doped La2O3 is not a good catalyst for methane activation despite lowering the energy of oxygen-vacancy formation the most. We propose that it is likely that the experimental value for the oxygen-vacancy formation energy might be affected substantially by the presence of adventitious dopants, which will then affect catalytic activity as well. We suggest that dopants affect the energy of vacancy formation in two ways: a local modification of the bond strength of the oxygen atoms to the oxide and a global effect due to a change in the Fermi level, which, in turn, can affect the charge of the oxygen vacancy and its energy of formation.

IntroductionThe selective hydrogenation of a,b-unsaturated carbonyl compounds is of theoretical and practical significance. [1][2][3] For instance, the hydrogenation of cinnamaldehyde (CAL) can produce cinnamal alcohol (COL), hydrocinnamaldehyde (HALD), and/or hydrocinnamal alcohol (HALC; Scheme 1), but the selective production of COL is difficult because the hydrogenation of the C=C bond is thermodynamically favored over that of the C=O moiety. [1,4] Moreover, acetals and other unidentified high-molecular-weight compounds can also be produced in large quantities in these reactions. [4,5] Although much research has already been focused on this issue, the selective hydrogenation of a,b-unsaturated aldehydes remains a challenge.The selective hydrogenation of a,b-unsaturated aldehydes toward the unsaturated alcohol can be achieved with homogeneous catalysts such as metal hydrides, aluminium isopropoxide, and others. [6,7] However, it is desirable to develop an equal-ly selective heterogeneous catalyst as these are easier to handle and separate from the products. To this end, a large number of studies on supported catalysts based on Pt, Rh, Au, Ru, and Pd active phases have been reported. [8][9][10][11][12] Cordier et al. reported that the selectivity for COL production from CAL hydrogenation follows the sequence Os > Ir > Pt > Ru > Rh > Pd, [13,14] a trend that was correlated with the width of the dband of the metal (Pd < Pt < Ir, Os). Many other studies have targeted supported Pt catalysts because of their high activity and moderate selectivity.In addition to the different metals that can be used to control selectivity in CAL hydrogenation processes, the supports may play an important role to define the selectivity. Indeed, differences in activity and selectivity may be obtained by varying the nature of the interaction between the support and nanoparticles (NPs). For instance, the selectivity toward COL production may be enhanced by using reducible oxides such as CeO 2 , [15] MnO 2 , [16] SnO 2 , [17] TiO 2 , [18] and ZnO [19] because of the electron transfer that takes place between these supports and Catalysts made of Pt nanoparticles dispersed on graphene (X wt %Pt/G, X = 2.0, 3.5, and 5.0) were prepared and characterized by XRD, Raman spectroscopy, BET surface area measurements, TEM, and X-ray photoelectron spectroscopy (XPS), and a 3.5 wt % Pt supported on Vulcan Carbon catalyst (3.5 wt %Pt/ VC) was included as a reference. Although the mean Pt nanoparticle size is approximately 4.4 nm for all X wt %Pt/G and 3.5 wt %Pt/VC catalysts, cinnamal alcohol was produced with high selectivity only with the graphene-supported catalysts:92 % conversion and 88 % selectivity toward cinnamal alcohol were obtained with 3.5 wt %Pt/G. This catalyst also showed good stability in recycling tests. The good selectivity observed with the graphene-based catalysts is attributed to the higher fraction of reduced surface Pt 0 atoms seen on the surface of the Pt nanoparticles (determined by XPS). This interpretation is consistent with D...