Active sites engineering of Pt/CNT oxygen reduction catalysts by atomic layer deposition

Understanding carbon-supported Pt-catalyzed oxygen reduction reaction(ORR)from the perspective of the active sites is of fundamental and practical importance.In this study,three differently sized carbon nanotube-supported Pt nanoparticles(Pt/CNT)are prepared by both atomic layer deposition(ALD)and impregnation methods.The performances of the catalysts toward the ORR in acidic media are comparatively studied to probe the effects of the sizes of the Pt nanoparticles together with their distributions,electronic properties,and local environments.The ALD-Pt/CNT catalysts show much higher ORR activity and selectivity than the impregnation-Pt/CNT catalysts.This outstanding ORR performance is ascribed to the well-controlled Pt particle sizes and distributions,desirable Pt^04f binding energy,and the Cl-free Pt surfaces based on the electrocatalytic measurements,catalyst characterizations,and model calculations.The insights reported here could guide the rational design and fine-tuning of carbon-supported Pt catalysts for the ORR.

Platelet carbon nanofibers as support of Pt-CoO electrocatalyst for superior hydrogen evolution

Exploration of cost-effective Pt/C catalysts has been a significant issue for electrochemical hydrogen evolution reaction(HER) toward sustainable energy conversion and storage.Herein,we report a fabrication strategy by employing platelet carbon nanofibers(p-CNF) as the support to immobilize Pt-CoO HER electrocatalyst using atomic layer deposition method.The edge-rich p-CNF support is found to act as the anchoring sites of Pt nanoparticles and favorably capture electrons from Pt to yield electron-deficient Pt surfaces for the boosted HER.Additionally,the sequential growth of CoO onto the Pt/p-CNF catalyst elaborately constructs the Pt-CoO interface and facilitates the electron transfer from Pt to CoO,which further enhances the HER activity.These advantages endow the fabricated Pt-CoO/p-CNF catalyst with the superior HER activity,e.g.,a very low overpotential of 26 mV at the current density of 10 mA·cm-2 and a mass activity of 4.42 A·mgPt-1at the overpotential of 30 mV,18.8 times higher than that of the commercial20 wt% Pt/C catalyst.The insights reported here could shed light on for the fabrication of cost-effective Pt-based composite HER catalysts.

Mapping three-dimensional co-seismic surface deformations associated with the 2015 MW7.2 Murghab earthquake based on InSAR and characteristics of crustal strain

Three-dimensional(3 D) co-seismic surface deformations are of great importance to interpret the characteristics of coseismic deformations and to understand the geometries and dynamics of seismogenic faults. In this paper, we propose a method for mapping 3 D co-seismic deformations based on InSAR observations and crustal strain characteristics. In addition, the search strategy of correlation points is optimized by adaptive correlation distance, which greatly improves the applicability of the proposed method in restoring deformations in decorrelation areas. Results of the simulation experiment reveal that the proposed method is superior to conventional methods in both the accuracy and completeness. The proposed method is then applied to map the 3 D co-seismic surface deformations associated with the 2015 MW7.2 Murghab earthquake using ascending and descending ALOS-2 PALSAR-2 images. The results show that the seismogenic fault is the Sarez-Karakul fault(SKF), which is dominated by NE-SW strike slips with an almost vertical dip angle. The north section and the south segment near the epicentre have obvious subsidence along with a southwestward motion in the northwest wall, and the southeast wall has northeast movement and surface uplift trend along the fault zone. The strain field of the earthquake is also obtained by the proposed method. It is found that the crustal block of the seismic area is obviously affected by dilatation and shear forces, which is in good agreement with the movement character of the sinistral slip.

Large Curvature Folding Strategies of Butterfly Proboscis

Due to its real-time control,high folding ratio,and structure self-locking,flexible large curvature self-folding devices have broad application prospects,such as foldable human implants,flexible electronics,and flexible robots.Driven by this background,flexible large curvature folding butterfly(Polyura eudamippus)proboscises were studied in this work.The folding ratio of the proboscises was about 15.The curvature of coiled proboscises ranged from about 150 m_1 to 880 m The external and internal structures of the proboscises were studied by different methods.Three main strategies for large-curvature folding of proboscises were identified:a gradual decrease in thickness,a lower elastic modulus,and(most importantly)large numbers of regular corrugated cracks arranged on the surface.These corrugated cracks can effectively accommodate the coiled strain and provide space for the large curvature folding of proboscises.Finally,a 4D printed coiled sample with corrugated cracks was fabricated to mimic the proboscises stretching process.Large-curvature folding strategies,based on these proboscises,provide insights for the biomimetic design of artificial highly folded components.