Yan-Xia Jiang

Adsorption and oxidation of ethanol on colloid-based Pt/C, PtRu/C and Pt3Sn/C catalysts: In situ FTIR spectroscopy and on-line DEMS studies

The interaction of colloid-based, carbon supported Pt/C (40 wt%), PtRu/C (45 wt%) and Pt3Sn/C (24 wt%) catalysts with ethanol and their performance for ethanol electrooxidation were investigated in model studies by electrochemical, in situ infrared spectroscopy and on-line differential electrochemical mass spectrometry measurements. The combined application of in situ spectroscopic techniques on realistic catalysts and under realistic reaction (DEMS, IR) and transport conditions (DEMS) yields new insight on mechanistic details of the reaction on these catalysts under the above reaction and transport conditions. Based on these results, the addition of Sn or Ru, though beneficial for the overall activity for ethanol oxidation, does not enhance the activity for C-C bond breaking. Dissociative adsorption of ethanol to form CO2 is more facile on the Pt/C catalyst than on PtRu/C and Pt3Sn/C catalysts within the potential range of technical interests (<0.6 V), but Pt/C is rapidly blocked by an inhibiting CO adlayer. In all cases acetaldehyde and acetic acid are dominant products, CO2 formation contributes less than 2% to the total current. The higher ethanol oxidation current density on the Pt3Sn/C catalyst at these potentials results from higher yields of C2 products, not from an improved complete ethanol oxidation to CO2.

Silver nanoparticles confined in SBA-15 mesoporous silica and the application as a sensor for detecting hydrogen peroxide

Silver nanoparticles within the pore channels of selectively grafted mesoporous silica SBA-15 were synthesized. Silanols on the external surface of as-SBA-15 were first capped by -Si(CH3)3 groups. After removal of the template of capped SBA-15 by calcination, silanols on the internal surface of SBA-15 were modified by 3-aminopropyltrimethoxysilane (APTMS), and then formaldehyde was grafted by amino groups of APTMS, and further Ag(NH3)2NO3SBA-15). High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), nitrogen adsorption/desorption isotherms, and UV-vis spectra confirm that the silver nanoparticles have been confined inside the channels of SBA-15. In addition, the Ag-mSBA-15 modified electrode (Ag-mSBA-15/GC) exhibited an excellent electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2). The proposed H2O2 sensor exhibits a linear range of 48.5 µM-0.97M with a detection limit of 12 µM (S/N = 3 ) and analytical time of 10 seconds per sample.

Flavins mediate extracellular electron transfer in Gram-positive Bacillus megaterium strain LLD-1

The extracellular electron transfer (EET) mechanism of an isolated Gram-positive Bacillus megaterium strain (LLD-1), identified by 16S rRNA gene sequencing and physiological analysis, was investigated in the present study. The electrochemical activity of strain LLD-1 was confirmed by electrochemical E-t and amperometric I-t tests. Flavins in culture suspension from strain LLD-1 were further proved to be able to act as electron shuttles, strengthening the electron transfer from LLD-1 to the electrode. The output voltage and current output were increased 2.8 times and 3.7 times, respectively, by adding 100nM exogenetic flavins into microbial fuel cells inoculated with LLD-1. Electricity generation by LLD-1 from different carbon sources can be enhanced by adding 100nM exogenetic flavins. This study indicated that flavins were essential to the EET process of the Gram-positive strain LLD-1. Furthermore, a putative EET model for B. megaterium strain LLD-1 and even for Gram-positive bacteria was proposed.

Preparation and characterization of a novel composite microporous polymer electrolyte for Li-ion batteries

A novel composite microporous polymer electrolyte composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and mesoporous SBA-15 was prepared. The composite solid polymer electrolyte (CSPE) exhibits ionic conductivity as high as 0.30 mS·cm −1 with a composition of SBA-15 : PVdF-HFP=3 : 8 at room temperature. Infrared transmission spectroscopic results suggested that the mechanism of micropore formation is similar to that of the phase inversion. X-ray diffraction (XRD) results demonstrated that the addition of SBA-15 inhibits the crystallization of PVdF-HFP, while the SBA-15 preserves well its ordered mesoporous structure during the course of preparation. The Li/CSPE/MCF of half-cell was assembled, and it showed a good electrochemical and cyclability performance during charge-discharge cycles.

Special IR properties of palladium nanoparticles and their aggregations in CO molecular probe infrared spectroscopy

Dispersed Pd nanoparticles (Pdπ) have been synthesized by reducing H2PdCl4 with ethanol, and stabilized using poly(vinylpyrrolidone) (PVP). The Pdπ is applied to the glassy carbon substrate to form a thin film, and then the potential cyclic scanning at 50 mV-s−1 from -0.25 to 1.25 V was carried out for about 30 min to form the aggregations of Pdπ (Pdagπ). FTIR spectroscopy of both transmission and reflection modes was employed to study CO adsorption on Pdπ and Pdagπ in both solid|liquid and solid|gas interfaces. It has been revealed that CO adsorption on Pdπ film yields two IR bands near 1964 and 1906 cm−1, which are assigned to IR absorption of CO bonded on asymmetric and symmetric bridge sites, respectively. In contrast to the IR properties of CO adsorbed on Pdπ, only species of CO bonded on asymmetric bridge sites was determined on Pdagπ, and the direction of the IR band near 1963 cm−1 is completely inverted. The full width at half-maximum (FWHM) of the COasinB band near 1964 cm−1 is measured to be 14 cm−1 on Pdπ film, while it is 24 cm−1 on Pdagπ film. The results of the present study demonstrated that the inverting of the IR band direction is a general phenomenon that is closely related to the interaction between nanoparticles in aggregation of Pdπ.

Interactions between iron mineral-humic complexes and hexavalent chromium and the corresponding bio-effects

The interfacial behaviors of chromium are fundamental for understanding the environmental effects of chromium in contaminated environments. However, complex surfaces can cause chromium to exhibit a variety of behaviors, especially when humic substances are considered. This work illustrated the role of humics (humic acid and fulvic acid) during the adsorption of Cr(VI) onto iron minerals (magnetite and hematite). The interfacial behaviors were investigated through their adsorption kinetics, adsorption isotherms, and thermodynamics. Then, the microbial diversity was monitored to reflect the bio-effects of Cr(VI) adsorbed onto four iron oxide-humic complexes. The differences in the adsorption capacities and mechanisms of Cr(VI) on the surfaces of the iron mineral-humic complexes were observed. Humics obviously decreased the adsorption capacities of Cr(VI) on the hematite complexes and relieved the decline in the microbial diversity; meanwhile, humics imposed relatively insignificant changes to the Cr(VI) adsorption capacity onto the magnetite complexes. Thus, the corresponding microbial diversity might be mainly affected by released micelles formed by Cr(VI) and humics. These results illustrate the complexities of the interfacial behaviors of Cr(VI) on the surfaces of iron mineral-humic complexes and broaden the current understanding of chromium migration and transportation.

Rational Design and Synthesis of Low-Temperature Fuel Cell Electrocatalysts

Recent progresses in proton exchange membrane fuel cell electrocatalysts are reviewed in this article in terms of cathodic and anodic reactions with a focus on rational design. These designs are based around gaining active sites using model surface studies and include high-index faceted Pt and Pt-alloy nanocrystals for anodic electrooxidation reactions as well as Pt-based alloy/core–shell structures and carbon-based non-precious metal catalysts for cathodic oxygen reduction reactions (ORR). High-index nanocrystals, alloy nanoparticles, and support effects are highlighted for anodic catalysts, and current developments in ORR electrocatalysts with novel structures and different compositions are emphasized for cathodic catalysts. Active site structures, catalytic performances, and stability in fuel cells are also reviewed for carbon-based non-precious metal catalysts. In addition, further developmental perspectives and the current status of advanced fuel cell electrocatalysts are provided.Graphical Abstract

Chapter 12 - Nanocrystal Catalysts of High-Energy Surface and Activity

Metal and metal oxide nanocrystals (NCs) enclosed by high-surface-energy facets (or high-energy surface) have attained enormous attention. The NCs of high-energy surface are thermodynamically unstable in their growth, resulting in a big challenge in the shape-controlled synthesis. To achieve this purpose, the indispensable kinetic control by electrochemical method or surfactant-based wet chemical route is widely exploited. Currently, high-energy surface monometallic NCs, such as Pt and Pd, and bimetallic NCs (surface decoration, alloy, and core-shell structure) are successfully synthesized. These metal NCs of uniform single crystallographic form as tetrahexahedron (THH), trapezohedron (TPH), hexoctahedron (HOH), or their concave morphology exhibit a remarkable performance in heterogeneous catalysis, electrocatalysis, and analysis. Apart from metal NCs, metal oxide NCs enclosed with high-surface-energy facets, such as TiO2 and BiVO4, present also an extensive application in photocatalysis, that is, water-splitting and dye-sensitized solar cells. The catalytic activity of NCs enclosed with high-energy facets possessing a high density of active sites is greatly enhanced compared with NCs enclosed with low-energy facets. More importantly, the NCs enclosed with high-energy facets provide a promising platform to fundamentally understand the principles in surface science and heterogeneous catalysis, shedding therefore new light on the rational design of practical catalysts with high activity, selectivity, and durability for energy conversion and storage. Future opportunity and challenge of NC catalysts of high-energy surface may consist in the fundamental understanding of surface structure-catalytic functionality of NCs in different catalytic environments and the development of synthesis technology to reach a rational design and mass production of supported NC catalysts with adjustable high-energy surface structure, controllable particle size, diversified substrate, and variable loadings for realistic applications.

Chapter 9:Nanoelectrochemistry in the people’s republic of China

This chapter reviews the main progresses on nanoelectrochemistry made in China during the last decade. It begins with an overview of the financial supports for electrochemistry studies from natural science foundation of China (NSFC), and follows with a survey about the publications and citations of papers contributed by Chinese researchers on nanoelectrochemistry. After a brief introduction of the main academic activities on electrochemistry in China, including the Chinese Society of Electrochemistry (CSE), the national conferences of electrochemistry and the Journal of Electrochemistry (the CSE sponsored journal), the chapter has summarized the major progresses made by Chinese researchers on nanoelectrochemistry in the period from 2001 to 2012, which consist in (1) High surface energy nanomaterials — shape-controlled synthesis and properties; (2) Enhanced optical properties of nanomaterials and applications; (3) Surface nanostructure construction and nanofabrication; (4) Electroanalytical Chemistry and physical electrochemistry based on nanomaterials; and (5) Nanomaterials for electrochemical energy conversion and storage. The chapter is ended with a conclusion and prospective statement about further R&D of nanoelectrochemistry.