Multi-twinned gold nanoparticles with tensile surface steps for efficient electrocatalytic CO_(2) reduction

CO_(2) reduction reactions(CO_(2)RR) powered by renewable electricity can directly convert CO_(2) to hydrocarbons and fix the intermittent sustainable energy in portable chemical fuels. It is of great importance to develop advanced catalysts that can boost CO_(2)RR with high activity, selectivity, and efficiency at low overpotentials. Here, we report the solution synthesis using H_(2)O_(2) to modify the surface structures of gold multi-twinned nanoparticles(AuMPs) and create tensile surface steps. Calculations predicted significantly enhanced CO_(2) adsorption and boosted CO_(2)RR capabilities with inhibited hydrogen evolution reaction activity for the tensile surface steps with modified electronic structure. The H_(2)O_(2)-treated AuMPs with surface steps and 3.83% tensile lattices showed much higher activity and selectivity at lower overpotentials for CO_(2)RR than pristine gold nanoparticles.The CO-production current density reached about 98 mA cm^(-2) with a Faradaic efficiency of 95.7% at -0.30 V versus reversible hydrogen electrode in the flow cell, showing a half-cell energy efficiency as high as ~83%. Our strategy represents a rational catalyst design by engineering the surface structures of metal nanoparticles and may find more applicability in future electrocatalysis.

Adsorption and Vibration of O on the Pt Stepped Surfaces

The 5-parameter Morse potential （5-MP） of interaction between an adatom and metal surface cluster is put forward and performed on O-Pt stepped surface systems. We have primarily studied O/Pt（331）, O/Pt（221） and O/Pt（553） systems and drawn some conclusions from the calculated results in good agreement with experimental and theoretical information. The O atom adsorbs stably near the step, so the step is the active place in the reaction. There are two types of atomic states, β1 and β2, in the adsorbed systems, corresponding to the three-fold states and four-fold long-bridged state behind the step respectively. Moreover, the length of （Ⅲ） terrace affects weakly the properties of all critical points in these systems.

Oxygen Atom Adsorption and Diffusion on Pd Low-index Surfaces and (311) Stepped Surface

The 5-parameter Morse potential (5-MP for short) of the interaction system between an oxygen atom and palladium surface clusters was constructed. The adsorption and diffusion of an oxygen atom on low index surfaces Pd (100). Pd (111). Pd (110) and Pd (311) stepped surface were investigated in detail with 5-MP. It is found that fcc and hcp sites on the (111) surface and (111) microfacets are equivalent. The calculation results show that O atom adsorbs in the three-fold hollow site, and the long-bridge site is a stable site both in regular Pd (110) surface and in the (1×2) missing-row reconstruction structure. Moreover, in the study of O-Pd (311) surface system, We conclude that there are two stable adsorption states (four-fold site: H4, three-fold site: Hn) on O-Pd (311) surface and the three-fold site (Hf) is the metastable adsorption. At low coverage oxygen atom favors the four-fold hollow site (H4).

Why a mosquito leg possesses superior load-bearing capacity on water:Experimentals

Mosquitoes possess the striking ability to walk on water because each of their legs has a huge water supporting force（WSF） that is 23 times their body weight.Aiming at a full understanding of the origins of this extremely large force,in this study,we concentrate on two aspects of it：the intrinsic properties of the leg surface and the active control of the initial stepping angle of the whole leg.Using a measurement system that we developed ourselves,the WSFs for the original leg samples are compared with those whose surface wax and microstructures have been removed and with those of a different stiffness.The results show that leg f exibility plays a dominant role over surface wax and microstructures on the leg surface in creating the supporting force.Moreover,we discuss the dependence relationship between the maximum WSF and the initial stepping angle,which indicates that the mosquito can regulate this angle to increase or decrease the WSF during landing or takeoff.These finding are helpful for uncovering the locomotion mechanism of aquatic insects and for providing inspiration for the design of microfluids miniature boats,biomimetic robots,and microsensors.

Studies of surface processes of electrocatalytic reduction of CO_(2) on Pt(210), Pt(310) and Pt(510)

Surface processes of CO_(2)reduction on Pt(210),Pt(310),and Pt(510)electrodes were studied by cyclic voltammetry.Different surface structures of these platinum single crystal electrodes were obtained by various treatment conditions.The experimental results illustrated that the electrocatalytic activity of Pt single crystal electrodes towards CO_(2)reduction is decreased in an order of Pt(210)>Pt(310)>Pt(510),i.e.,with the decrease of(110)step density on well-defined surfaces.When the surfaces were reconstructed due to oxygen adsorption,the catalytic activity of all the three electrodes has been enhanced to a cer-tain extent.Although the activity order remains unchanged,the electrocatalytic activity has been en-hanced more significantly as the density of(110)step sites is more intensive on the Pt single crystal surface.It has revealed that the more open the surface structure is,the more active the Pt single crystal electrode will be,and the easier for the electrode to be transformed into a surface structure that exhib-its higher activity under external inductions.However,the relatively ordered surfaces of Pt single crystal electrode are comparatively stable under the same external inductions.The present study has gained knowledge on the interaction between CO_(2)and Pt single crystal electrode surfaces at a micro-scopic level,and thrown new insight into understanding the surface processes of electrocatalytic re-duction of CO_(2).

Frictional shear stress of ZnO nanowires on natural and pyrolytic graphite substrates

The friction behaviour of ZnO nanowires on natural graphite(NG)and highly oriented pyrolytic graphite(HOPG)substrates was tested in ambient conditions by use of optical microscopy based nanomanipulation.Nanowires on the step-free and waviness-free NG substrate exhibit a diameter-independent nominal frictional shear stress of 0.48 MPa,and this provides a benchmark for studying how the surface topography of graphite influences nanowire friction.Nanowires on the HOPG substrate present a significant diameter-dependent frictional shear stress,increasing from 0.25 to 2.78 MPa with the decrease of nanowire diameter from 485 to 142 nm.The waviness of HOPG has a limited effect on the nanowire friction,as a nanowire can fully conform to the substrate.The surface steps on the HOPG can significantly enhance the nanowire friction and lead to a much higher frictional shear stress than that on NG due to mechanical blocking and the presence of a Schwoebel barrier at step edges.The surface steps,however,can also generate small wedge-shaped gaps between a nanowire and substrate,and thus reduce the nanowire friction.With the decrease in nanowire diameter,the capacity for the nanowire to better conform to the substrate reduces the length of the wedge-shaped gaps,leading to the observed increase in nanowire friction.The results have improved our understanding of the unique friction behaviour of nanowires.Such an improved understanding is expected to benefit the design and operation of nanowire-friction-based devices,including bio-inspired fibrillar adhesives,soft grippers,rotary nanomotors,and triboelectric nanogenerators.

Effect of H_2O_2 and nonionic surfactant in alkaline copper slurry

For improving the polishing performance, in this article, the roles of a nonionic surfactant（Fatty alcohol polyoxyethylene ether） and H2O2 were investigated in the chemical mechanical planarization process, respectively.Firstly, the effects of the nonionic surfactant on the within-wafer non-uniformity（WIWNU） and the surface roughness were mainly analyzed. In addition, the passivation ability of the slurry, which had no addition of BTA, was also discussed from the viewpoint of the static etch rate, electrochemical curve and residual step height under different concentrations of H2O2. The experimental results distinctly revealed that the nonionic surfactant introduced in the slurry improved the WIWNU and surface roughness, and that a 2 vol% was considered as an appropriate concentration relatively. When the concentration of H2O2 surpasses 3 vol%, the slurry will possess a relatively preferable passivation ability, which can effectively decrease the step height and contribute to acquiring a flat and smooth surface. Hence, based on the result of these experiments, the influences of the nonionic surfactant and H2O2 are further understood, which means the properties of slurry can be improved.