在4H晶相Au纳米带上外延生长非常规晶相4H-Pd基合金纳米结构用于高效甲醇电催化氧化

Pd基合金纳米材料通常具有传统的面心立方(fcc)晶相。本文以密排六方4H相Au(4H-Au)纳米带为模板,外延生长非常规4H晶相的PdFe、PdIr和PdRu,形成4H-Au@PdM(M=Fe、Ir和Ru)核壳合金纳米带。合成的4H-Au@PdFe纳米带被用于碱性环境中甲醇电催化氧化反应(MOR)的催化剂,表现出优越的质量活性(3.69 A·mgPd^(−1)),分别为Pt/C和Pd黑催化剂质量活性的2.4和10.5倍,也跻身于最好的Pd基和Pt基MOR电催化剂之列。这一策略为合理设计和可控合成具有非常规晶相的多金属纳米结构提供了策略,从而为深入研究多金属纳米结构晶相依赖的性质和应用提供了可能。

二维材料最新研究进展

Research on two-dimensional(2D) materials has been explosively increasing in last seventeen years in varying subjects including condensed matter physics, electronic engineering, materials science, and chemistry since the mechanical exfoliation of graphene in 2004. Starting from graphene, 2D materials now have become a big family with numerous members and diverse categories. The unique structural features and physicochemical properties of 2D materials make them one class of the most appealing candidates for a wide range of potential applications. In particular, we have seen some major breakthroughs made in the field of 2D materials in last five years not only in developing novel synthetic methods and exploring new structures/properties but also in identifying innovative applications and pushing forward commercialisation. In this review, we provide a critical summary on the recent progress made in the field of 2D materials with a particular focus on last five years. After a brief backgroundintroduction, we first discuss the major synthetic methods for 2D materials, including the mechanical exfoliation, liquid exfoliation, vapor phase deposition, and wet-chemical synthesis as well as phase engineering of 2D materials belonging to the field of phase engineering of nanomaterials(PEN). We then introduce the superconducting/optical/magnetic properties and chirality of 2D materials along with newly emerging magic angle 2D superlattices. Following that, the promising applications of 2D materials in electronics, optoelectronics, catalysis, energy storage, solar cells, biomedicine, sensors, environments, etc. are described sequentially. Thereafter, we present the theoretic calculations and simulations of 2D materials. Finally, after concluding the current progress, we provide some personal discussions on the existing challenges and future outlooks in this rapidly developing field.

Tandem catalysis in electrochemical CO_(2) reduction reaction

Electrochemical CO_(2) reduction reaction(CO_(2)RR)is an attractive pathway for closing the anthropogenic carbon cycle and storing intermittent renewable energy by converting CO_(2) to valuable chemicals and fuels.The production of highly reduced carbon compounds beyond CO and formate,such as hydrocarbon and oxygenate products with higher energy density,is particularly desirable for practical applications.However,the productivity towards highly reduced chemicals is typically limited by high overpotential and poor selectivity due to the multiple electron-proton transfer steps.Tandem catalysis,which is extensively utilized by nature for producing biological macromolecules with multiple enzymes via coupled reaction steps,represents a promising strategy for enhancing the CO_(2)RR performance.Improving the efficiency of CO_(2)RR via tandem catalysis has recently emerged as an exciting research frontier and achieved significant advances.Here we describe the general principles and also considerations for designing tandem catalysis for CO_(2)RR.Recent advances in constructing tandem catalysts,mainly including bimetallic alloy nanostructures,bimetallic heterostructures,bimetallic core-shell nanostructures,bimetallic mixture catalysts,metal-metal organic framework(MOF)and metal-metallic complexes,metal-nonmetal hybrid nanomaterials and copper-free hybrid nanomaterials for boosting the CO_(2)RR performance are systematically summarized.The study of tandem catalysis for CO_(2)RR is still at the early stage,and future research challenges and opportunities are also discussed.

Crystal phase-controlled growth of PtCu and PtCo alloys on 4H Au nanoribbons for electrocatalytic ethanol oxidation reaction

Crystal phase can greatly affect the physicochemical properties and applications of nanomaterials.However,it stil remains a great challenge to synthesize nanostructures with the same composition and morphology but different phases in order to explore the phase-dependent properties and applications.Herein,we report the crystal phase-controlled synthesis of PtCu alloy shells on 4H Au nanoribbons(NRBs),referred to as 4H-Au NRBs,to form the 4H-Au@PtCu core-shell NRBs.By tuning the thickness of PtCu,4H-PtCu and face-centered cubic(cc)phase PICu(cc-PtCu)alloy shells are successtully grown on the 4H-Au NRB cores.This thickness-dependent phase-controlled growth strategy can also be used to grow PtCo alloys with 4H or fcc phase on 4H-Au NRBs.Significantly,when used as electrocatalysts for the ethanol oxidation reaction(EOR)in alkaline media,the 4H-Au@4H-PtCu NRBs show much better EOR performance than the 4H-Au@fcc-PtCu NRBs,and both of them possess superior performance compared to the commercial Pt black.Our study provides a strategy on phase-contolled synthesis of nanomaterials used for crystal phase-dependent applications.

Hard nanocrystalline gold materials prepared via high-pressure phase transformation

As one of the important materials,nanocrystalline Au(n-Au)has gained numerous interests in recent decades owing to its unique properties and promising applications.However,most of the current n-Au thin films are supported on substrates,limiting the study on their mechanical properties and applications.Therefore,it is urgently desired to develop a new strategy to prepare nAu materials with superior mechanical strength and hardness.Here,a hard n-Au material with an average grain size of~40 nm is prepared by cold-forging of the unique Au nanoribbons(NRBs)with unconventional 4H phase under high pressure.Systematic characterizations reveal the phase transformation from 4H to face-centered cubic(fcc)phase during the cold compression.Impressively,the compressive yield strength and Vickers hardness(HV)of the prepared n-Au material reach~140.2 MPa and~1.0 GPa,which are 4.2 and 2.2 times of the microcrystalline Au foil,respectively.This work demonstrates that the combination of high-pressure cold-forging and the in-situ 4H-to-fcc phase transformation can effectively inhibit the grain growth in the obtained n-Au materials,leading to the formation of novel hard n-Au materials.Our strategy opens up a new avenue for the preparation of nanocrystalline metals with superior mechanical property.