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.

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.

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.

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.