Research perspectives for catalytic valorization of biomass

Efficient utilization of biomass for the supply of energy and synthetic materials would mitigate the heavy reliance on fossil resources and the growing CO_(2) emission, thus contributing to establishing sustainable and carbon–neutral societies. Much effort has been devoted to catalytic transformations of lignocellulosic biomass, the most abundant and nonedible form of biomass.

水在金属硫化矿体自燃中的作用

金属硫化矿物氧化起因于硫化矿石固液相界面的电化学反应。水是硫化矿石自热、自燃的关键。注水、石灰水及其他阻化剂的阻燃方法忽视了水溶液中游离氧在硫化矿物氧化过程中所起的巨大作用，因而收效甚微。注水对自燃的矿石有一定的物理降温作用，但对未燃矿石则起了电化学升温作用，对深部矿体则起了预热预氧化作用。

Bio-inspired carbon electro-catalysts for the oxygen reduction reaction

We report the synthesis, characterisation and catalytic performance of two nature-inspired biomassderived electro-catalysts for the oxygen reduction reaction in fuel cells. The catalysts were prepared via pyrolysis of a real food waste（lobster shells） or by mimicking the composition of lobster shells using chitin and CaCO3 particles followed by acid washing. The simplified model of artificial lobster was prepared for better reproducibility. The calcium carbonate in both samples acts as a pore agent, creating increased surface area and pore volume, though considerably higher in artificial lobster samples due to the better homogeneity of the components. Various characterisation techniques revealed the presence of a considerable amount of hydroxyapatite left in the real lobster samples after acid washing and a low content of carbon（23%）, nitrogen and sulphur（〈1%）, limiting the surface area to 23 m^2/g, and consequently resulting in rather poor catalytic activity. However, artificial lobster samples, with a surface area of ≈200 m^2/g and a nitrogen doping of 2%, showed a promising onset potential, very similar to a commercially available platinum catalyst, with better methanol tolerance, though with lower stability in long time testing over 10,000 s.

Unique Nafion-Os(bpy)3^(2+) Modified Electrodes

It was newly found that the electrodes modified by applying ethanol solutions of Nationcontaining os(bpy)32+ onto the substrate electrode (the one-step method) show two pairs of stableredox peaks of Os(bpy)32+/3+ on cyclic voltammogram near 0.54V and 0.25V, respectively. Thesemoditied electrodes can effectively mediate and catalyze the first and second steps of nitritereduction in acidic media in the potential region 0-0.9V when the loading in the coating (X=F(Os2+) / F(SO3-)) and pH in solution are below 0. 17 and 4, respectively. When X is between 0.33and 0. 17. only the current peak near 0.54V appears regardless of solution pH and only the first stepof NO2 reduction is catalyzed. Thus the modified electrode provides a very useful flexibility thatone can control the reaction pathway and catalytic activity of nitrite reduction by simply changingthe concentration of the mediator in the coating.

纳米氧化铜片用于高效电化学还原一氧化氮

一氧化氮电还原反应将工业废气转化为有价值的氨,表现出极具潜力的应用前景.在本工作中,我们合成了具有高比表面积和丰富缺陷的氧化铜纳米片催化剂,在流动池中氨法拉第效率达到92.1%,在-0.2 V vs.RHE时,一氧化氮电还原电流密度和氨的生产速率分别达到1.1 A cm^(-2)和7356μmol cm^(-2)h^(-1).在电流密度超过400 m A cm-2时,氨法拉第效率在50小时保持在80%以上.准原位X射线光电子能谱和原位X射线吸收光谱结果表明氧化铜纳米片在一氧化氮电还原过程中被电化学还原成单质铜.与铜纳米颗粒相比,氧化铜纳米片展现出较高的电化学表面积和一氧化氮电还原的内在活性.

Self-powered electrochemical water treatment system for pollutant degradation and bacterial inactivation based on high-efficient Co(OH)_(2)/Pt electrocatalyst

Electrochemical system with electro-Fenton reaction is an effective pathway for oxidative degradation of refractory organic pollutants for water treatment.However,the method is limited by the low catalytic efficiency and high electrical cost in practical applications.This work presents a self-powered and high-efficient electrochemical system for water treatment including pollutant degradation and bacterial inactivation,which is composed of a self-powered triboelectric nanogenerator(TENG)converting mechanical energy into electrical energy,a power management circuit integrated with a supercapacitor to store the harvesting electrical energy temporarily,and an electrochemical setup integrated with two-dimentional Co(OH)_(2)/Pt nanosheet as electrocatalyst.The nanocatalyst,ultrafine Pt nanoparticles(Pt NPs)loaded on Co(OH)_(2) nanosheet(Co(OH)_(2)/Pt),is synthesized by a facile one step hydrothermal reaction without any surfactant,which can improve H_(2)O_(2)and hydroxyl radical production via redox reaction.This self-powered electrocatalytic system is able to degrade nearly 100%of organic pollutant within 100 min,and efficiently kill bacteria.This work shows great potential to develop high-efficient and self-powered electrochemical water treatment system through integrating TENG and nanocatalyst.

H_(2)O_(2) treatment boosts activity of NiFe layered double hydroxide for electro-catalytic oxidation of urea

Urea oxidation reaction(UOR)provides a method for hydrogen production besides wastewater treatment,but the current limited catalytic activity has prevented the application.Herein,we develop a novel H_(2)O_(2) treatment strategy for tailoring the surface oxygen ligand of NiFe-layered double hydroxides(NiFe-LDH).The sample after H_(2)O_(2) treatment(NiFeOLDH)shows significant enhancement on UOR efficiency,with the potential of 1.37 V(RHE)to reach a current density of 10 mA/cm^(2).The boost is attributed to the richness adsorption O ligand on NiFeO-LDH as revealed by XPS and Raman analysis.DFT calculation indicates formation of two possible types of oxygen ligands:adsorbed oxygen on the surface and exposed from hydroxyl group,lowered the desorption energy of CO_(2) product,which lead to the lowered onset potential.This strategy is further extended to NiFe-LDH nano sheet on Ni foam to reach a higher current density of 440 mA/cm^(2) of UOR at 1.8 V(RHE).The facile surface O ligand manipulation is also expected to give chance to many other electro-catalytic oxidations.

PtxCuy nanocrystals with hexa-pod morphology and their electrocatalytic performances towards oxygen reduction reaction

Bimetallic PtxCuy nanocrystals （NCs） with well-defined hexa-pod morphology were synthesized via a wet chemistry approach. The as-synthesized convex NCs with dimensions of around 20 nm show exposed low-index （111） facets on the seeds and various high-index facets on the pods. The growth mechanism involved preferred growth along the 〈100〉 crystallographic direction on cuboctahedral seeds. The synthetic protocol could be applied to the synthesis of PtxCuy NCs with various Cu/Pt ratios. The electro-catalytic activity of the hexa-pod PtxCuy NCs supported on carbon black towards the oxygen reduction reaction （ORR） was studied. The hexa-pod PtCu2/C catalysts exhibit the highest specific activity （3.7 mA/cm^2pt） and mass activity （2.4 A/mget） reported to date for PtxCuy. Comparison with other morphological forms of PtxCuy indicated that the enhanced activity originated from morphological factors. The existence of high-index facets as well as abundant edges and steps on the pods could reasonably explain the enhanced catalytic activity. The hexa-pod PtxCuy/C catalysts also show high morphological stability and activity after accelerated durability tests. The as-synthesized hexa-pod PtxCuy NCs have high potential as cathode electro-catalysts for proton exchange membrane fuel cells.

One-step synthesis of the PdPt bimetallic nanodendrites with controllable composition for methanol oxidation reaction

This paper demonstrates a one-pot approach to produce highly dispersed dendritic palladium-platinum bi- metallic nanoparticles （NPs） with small particle size, tunable composition and high catalytic activity. Herein, the PdPt bi- metallic NPs have been obtained using bayberry tannin （BT） as both the reducing agent and surfactant. Additionally, the PdPt bimetallic NPs with different Pd/Pt atomic ratios can be prepared by just varying the amounts of the Pd and Pt pre- cursors. Most importantly, the as-prepared Pd52Pt4s catalyst exhibits the optimal catalytic activities compared with the other compositional PdPt NPs （Pds2Ptls, Pd69Ph~, and Pd36 Pt64） and commercial Pt/C （20 wt.%） catalyst for the methanol oxidation reaction （MOR）. Meanwhile, Pd52Pt4s also shows better CO tolerance, which can be attributed to the unique dendritic structure and the synergistic effect between Pd and Pt. With evident advantages of the facile preparation and enhanced catalytic performance, it holds great promise as a high-performance catalyst for electrochemical energy con- version.

Direct catalytic nitrogen oxide removal using thermal, electrical or solar energy

Considering the significant importance in both ecological and environmental fields, converting nitrogen oxide(NO_(x), especially NO) into value-added NH3or harmless N2lies in the core of research over the past decades. Exploring catalyst for related gas molecular activation and highly efficient reaction systems operated under low temperature or even mild conditions are the key issues. Enormous efforts have been devoted to NO removal by utilizing various driving forces, such as thermal, electrical or solar energy,which shine light on the way to achieve satisfying conversion efficiency. Herein, we will review the stateof-the-art catalysts for NO removal driven by the above-mentioned energies, including a comprehensive introduction and discussion on the pathway and mechanism of each reaction, and the recent achievements of catalysts on each aspect. Particularly, the progress of NO removal by environmentally friendly photocatalysis and electrocatalysis methods will be highlighted. The challenges and opportunities in the future research on the current topic will be discussed as well.

Single entity electrochemistry and the electron transfer kinetics of hydrazine oxidation

The mechanism and kinetics of the electro-catalytic oxidation of hydrazine by graphene oxide platelets randomly decorated with palladium nanoparticles are deduced using single particle impact electrochemical measurements in buffered aqueous solutions across the pH range 2–11. Both hydrazine, N2H4, and protonated hydrazine N2H5+ are shown to be electroactive following Butler-Volmer kinetics, of which the relative contribution is strongly pH-dependent. The negligible interconversion between N2H4 and N2H5+ due to the sufficiently short timescale of the impact voltammetry, allows the analysis of the two electron transfer rates from impact signals thus reflecting the composition of the bulk solution at the pH in question. In this way the rate determining step in the oxidation of each specie is deduced to be a one electron step in which no protons are released and so likely corresponds to the initial formation of a very short-lived radical cation either in solution or adsorbed on the platelet. Overall the work establishes a generic method for the elucidation of the rate determining electron transfer in a multistep process free from any complexity imposed by preceding or following chemical reactions which occur on the timescale of conventional voltammetry.