Concentration-dependent Morphology Control of Pt-coated-Ag Nanowires and Effects of Bimetallic Interfaces on Catalytic Activity

Silver nanowires （NWs） coated with platinum （Pt） nanoparticles were synthesized via a galvanic partial replacement of Ag NWs in an aqueous K2PtC16 solution at room temperature. The products were char- acterized using a combination of electron microscopies, selected area electron diffraction, energy- dispersive X-ray mapping and X-ray diffraction. The surface morphology and Pt/Ag composition ratios are controlled by adjusting the K2PtC16 concentration. Different concentrations result in various surface morphologies including rough nanoparticle coating, porous and relatively smooth surfaces. The forma- tion mechanism was discussed based on the lattice constants＇ difference, concentration driven nucleation, consumption of Ag NWs, and stoichiometry of the replacement reaction. The effects of the bimetallic interface on the catalytic activity toward the reduction of 4-nitrophenol by sodium borohydride were studied. The activity of Ag-Pt NWs is highly enhanced over monometallic nanostructures, and opti- mized by a low Pt loading of 1.34 at.%, which indicates a catalytic role of the inter-metallic interface for the elecrrnn transfer.

Experimental research on electromagnetic continuous casting high-speed steel composite roll

A high speed steel composite roll billet was fabricated, which is regular in shape, smooth in surface, slight in trace, compact in internal structure, free of slag inclusion, shrinkage cavity, cracks and other flaws, and good in macro quality of junction surface using a vertical continuous casting machine. The interface zone microstructure of bimetallic in billet of high speed steel composite roll was analyzed by metallurgical microscope(OM), X-ray diffractmeter(XRD), scanning electron microscopy(SEM) and energy-dispersive X-ray analysis(EDS). The results indicate that the microstructure of roll billet is composed of chilled solidified layer, dendrite zone, interfacial zone of bimetal and core material zone. The microstructure of outer shell material is composed of martensite + bainite + residual austenite + some small labyrinth-shape, small-short lath-shape, or dollop-shape eutectic carbides. The microstructure of core material is slice-shape pearlite and a little ferrite along boundary of cells. The interface region microstructure of bimetallic composite roll consists of diffusion region, chilled solidified layer and columnar grain region.

Intimate atomic Cu-Ag interfaces for high CO2RR selectivity towards CH4 at low over potential

Developing highly efficient electrochemical catalysts for carbon dioxide reduction reaction(CO_(2)RR)provides a solution to battle global warming issues resulting from ever-increasing carbon footprint due to human activities.Copper(Cu)is known for its efficiency in CO_(2)RR towards value-added hydrocarbons;hence its unique structural properties along with various Cu alloys have been extensively explored in the past decade.Here,we demonstrate a two-step approach to achieve intimate atomic Cu-Ag interfaces on the surface of Cu nanowires,which show greatly improved CO_(2)RR selectivity towards methane(CH4).The specially designed Cu-Ag interfaces showed an impressive maximum Faradaic efficiency(FE)of 72%towards CH4 production at-1.17 V(vs.reversible hydrogen electrode(RHE)).

Effect of Al22Si/ZL102 bimetal interface fabricated by extrusion at neareutectic temperature

The Al22Si/ZL102 bimetal was designed and prepared by extrusion at near-eutectic temperature.The properties and fracture behaviors of different surface treatments between oxide film and zinc coating were compared between the Al22 Si and ZL102 bimetal.The average bonding strength of bimetal with intermittent oxide film interface was about 89.3MPa,which is higher than that of the bimetal fabricated by zinc coating method（about 76.3MPa）.During the process of extrusion,the oxidation film was extruded to crush and the metal was extruded through the micro-cracks of the oxidation film,then the two surfaces were joined together.Altogether,the results showed that extrusion at near-eutectic temperature is favorable for achieving a high-quality metallurgical bonded interface.

Interfaced Ag/Cu nanostructures derived from metal thiolate nanoplates:A highly selective catalyst for electrochemical reduction of CO_(2) to ethanol

Selective reduction of CO_(2) into liquid products such as ethanol through electrochemical catalysis is promising in storing renewable energy in more deliverable chemicals and balancing the carbon footprint in the environment.However,the lack of efficient catalysts for electrochemical CO_(2) reduction reaction(eCO_(2)RR)makes the promise challenging because the formation of C2+alcohols requires coupling reactions between the shallow reduction intermediates and deep reduction intermediates that are usually difficult to form on uniform catalyst surfaces simultaneously with appropriate transient kinetics.Herein,we report a new strategy for synthesizing bimetallic nanostructures with high densities of interfaced Ag/Cu boundaries,which facilitate the coupling reaction of the high‐oxidation‐number intermediates(CO)formed on the Ag surface and the low‐oxidation‐number intermediates(CHx)formed on the Cu surface.The synthesis relies on the electrochemical reduction of bilayered nanoplates made of silver thiolate and copper thiolate,resulting in Ag/Cu nanostructures exposing Ag surface,Cu surface,and the Ag/Cu interfaced boundaries.Balancing the accessible surface areas of the Ag surface,Cu surface,and Ag/Cu boundaries is beneficial for maximizing the activity and selectivity of eCO_(2)RR towards ethanol production.Faradaic efficiency of forming ethanol has been observed as high as about 50%using the Ag/Cu nanostructure catalyst with molar ratio nAg:nCu of 1:1.Moreover,the promoted coupling reaction at the Ag/Cu boundaries and surface modification with thiolate anions significantly suppress the undesirable hydrogen evolution reaction,particularly at high cathodic potentials,maintaining high energy efficiency for eCO_(2)RR.