A central topic in single-atom catalysis is building strong interactions between single atoms and the support for stabilization. Herein we report the preparation of stabilized single-atom catalysts via a simultaneous self-reduction stabilization process at room temperature using ultrathin two-dimensional Ti3–x C2T y MXene nanosheets characterized by abundant Ti-deficit vacancy defects and a high reducing capability. The single atoms therein form strong metal–carbon bonds with the Ti3–x C2T y support and are therefore stabilized onto the sites previously occupied by Ti. Pt-based single-atom catalyst (SAC) Pt1/Ti3–x C2T y offers a green route to utilizing greenhouse gas CO2, via the formylation of amines, as a C1 source in organic synthesis. DFT calculations reveal that, compared to Pt nanoparticles, the single Pt atoms on Ti3–x C2T y support feature partial positive charges and atomic dispersion, which helps to significantly decrease the adsorption energy and activation energy of silane, CO2, and aniline, thereby boosting catalytic performance. We believe that these results would open up new opportunities for the fabrication of SACs and the applications of MXenes in organic synthesis.

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Intrinsic self-healing and highly stretchable electro-conductive hydrogels demonstrate wide-ranging utilization in intelligent electronic skin. Herein, we propose a new class of strain sensors prepared by cellulose nanofibers (CNFs) and graphene (GN) co-incorporated poly (vinyl alcohol)-borax (GN-CNF@PVA) hydrogel. The borax can reversibly and dynamically associate with poly (vinyl alcohol) (PVA) and GN-CNF nanocomplexes as a cross-linking agent, providing a tough and flexible network with the hydrogels. CNFs act as a bio-template and dispersant to support GN to create homogeneous GN-CNF aqueous dispersion, endowing the GN-CNF@PVA gels with promoted mechanical flexibility, strength and good conductivity. The resulting composite gels have high stretchability (break-up elongation up to 1000%), excellent viscoelasticity (storage modulus up to 3.7 kPa), rapid self-healing ability (20 s) and high healing efficiency (97.7 ± 1.2%). Due to effective electric pathways provided by GN-CNF nanocomplexes, the strain sensors integrated by GN-CNF@PVA hydrogel with good responsiveness, stability and repeatability can efficiently identify and monitor the various human motions with the gauge factor (GF) of about 3.8, showing promising applications in the field of wearable sensing devices.

The gold-catalyzed acetylene hydrochlorination reaction is an important process to produce vinyl chloride monomer in the polyvinyl chloride industry. The traditional catalyst of carbon-supported AuCl 3 is inclined to be reduced by acetylene and lose its activity during the reaction process. Here, we presented the construction of Au I −N 3 active sites through single gold atom dispersed on g-C 3 N 4 (Au 1 /g-C 3 N 4 ), which shows robust catalytic performance toward acetylene hydrochlorination. The Au species is shown to have Au I oxidation state, and it is coordinated with three nitrogen atoms of tri-s-triazine repeating units, which is consistent with density functional theory (DFT) modeling and XAFS measurements. Through DFT study, we demonstrate that the Au I −N 3 sites tend to coordinate with HCl than C 2 H 2 in the initial reaction. The Au I −N 3 sites cannot be reduced into Au 0 oxidation state easily and thus maintain their activity as stable catalytic active sites. The single-atom-site Au catalyst with nitrogen coordination environment and corresponding electronic state provides an efficient pathway for acetylene hydrochlorination reaction.

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It is highly desired yet challenging to steer the CO 2 electroreduction reaction (CO 2 ER) toward ethanol with high selectivity, for which the evolution of reaction intermediates on catalytically active sites holds the key. Herein, we report that K doping in Cu 2 Se nanosheets array on Cu foam serves as a versatile way to tune the interaction between Cu sites and reaction intermediates in CO 2 ER, enabling highly selective production of ethanol. As revealed by characterization and simulation, the electron transfer from K to Se can stabilize Cu I species which facilitate the adsorption of linear *CO L and bridge *CO B intermediates to promote CÀ C coupling during CO 2 ER. As a result, the optimized K 11.2% -Cu 2 Se nanosheets array can catalyze CO 2 ER to ethanol as a single liquid product with high selectivity in a potential area from À 0.6 to À 1.2 V. Notably, it offers a Faradaic efficiency of 70.3 % for ethanol production at À 0.8 V with as is stable for 130 h.