Surface Engineered Ru_(2)Ni Multilayer Nanosheets for Hydrogen Oxidation Catalysis

The hydrogen oxidation reaction(HOR)in alkaline conditions is of great importance for the application of anion exchange membrane fuel cells(AEMFCs).However,the electrocatalysts for alkaline HOR generally suffer from the disadvantage of sluggish kinetics.Herein,we have fabricated Ru2Ni multilayered nanosheets(Ru2Ni MLNSs)in the layer-by-layer manner and engineered the surface properties via postannealing for efficient alkaline HOR.Detailed investigations reveal that such annealing at different temperatures can alter the surface properties of Ru2Ni MLNSs and thus regulate their adsorption abilities toward*H and*OH.In particular,the optimal catalyst exhibits a mass activity of 4.34 A mgRu−1 at an overpotential of 50 mV,which is 18.1 and 13.2 times higher than those of Ru/C(0.24 A mgRu−1)and Pt/C(0.33 A mgPt−1),respectively.Theoretical calculations indicate that the presence of surface O atoms can facilitate the HOR activity while the excessive coverage of O atoms on Ru2Ni surface leads to the strengthened H binding and the decay of HOR activity.This work not only provides an efficient catalyst for alkaline HOR,but it also may shed new light on the design of high-performance catalysts for electrocatalysis and beyond.We have fabricated Ru2Ni multilayer nanosheets(Ru2Ni MLNSs)and realized the surface engineering via an annealing process.Detailed investigations show that such surface engineering can regulate the surface properties and thus promote the alkaline HOR activity.Consequently,the optimal catalyst exhibits a much higher activity than those of commercial Ru/C and Pt/C and is a promising catalyst for alkaline HOR.

Structural and Mechanistic Aspects of Mn-oxo and Co-based Compounds in Water Oxidation Catalysis and Potential Applications in Solar Fuel Production

To address the issues of energy crisis and global warming, novel renewable carbon-free or carbon-neutral energy sources must be identified and developed. A deeper understanding of photosynthesis is the key to provide a solid foundation to facilitate this transformation. To mimic the water oxidation of photosystem II oxygen evolving complex, Mn-oxo complexes and Co-phosphate catalytic material were discovered in solar energy storage. Building on these discoveries, recent advances in solar energy conversion showed a compelling working principle by combing the active Mn-oxo and Co-based catalysts in water splitting with semiconductor heteronanostructures for effective solar energy harnessing. In this review the appealing systems including Mn-oxo tetramer/Nafion, Mn-oxo dimer/TiO2, Mn-oxo oligomer/WO3, Co-Pi/Fe2O3, and Co-Pi/ZnO are summarized and discussed. These accomplishments offer a promising framework and have a profound impact in the field of solar fuel production.

UV-Shielding and Catalytic Characteristics of Nanoscale Zinc-Cerium Oxides

Fine particles of zinc-cerium oxides （ZCO） used as an ultraviolet filter were prepared via combustion synthesis route. The catalytic activity, UV-shielding performance, surface modification and application of ZCO in polyester varnish were discussed in detail. The experimental results indicate that the photo-catalytic activity of ZCO is much smaller than these of ZnO and TiO2; the oxidation catalytic activity of ZCO is far lower than that of CeO2; the ZCO has shown excellent ultraviolet absorption in the range of UV; addition modified ZCO （MZCO） into polyester will enhance the UV-shielding capability of polyester.

Effect of hydrogen impurities on hydrogen oxidation activity of Pt/C catalyst in proton exchange membrane fuel cells

High-purity of hydrogen is vital to the guarantee of end usage in proton exchange membrane fuel cell(PEMFC)electric vehicles(EVs)with superior durability and low expense.However,the currently employed hydrogen,primarily from fossil fuel,still contains some poisoning impurities that significantly affect the durability of PEMFCs.Here,we investigate the poisoning effect of several typical hydrogen impurities(S^(2-),Cl^(-),HCOO^(-)and CO_(3)^(2-))on the hydrogen oxidation reaction(HOR)of the state-of-the-art carbon-supported platinum(Pt/C)catalyst used in the PEMFC anode.Electrochemical results indicate that the electrochemically active surface area of Pt/C is hampered by these hydrogen impurities with reduced effective Pt reactive sites due to the competitive adsorption against hydrogen at Pt sites showing the extent of the poisoning on Pt sites in the order:S^(2-)>Cl^(-)>HCOO^(-)>CO_(3)^(2-).Density functional theory calculations reveal that the adsorption energy of S2-on Pt(111)is greater than that of Cl^(-),HCOO^(-)and CO_(2),and the electronic structure of Pt is found to be changed due to the adsorption of impurities showing the downshift of the d-band centre of Pt that weakens the adsorption of hydrogen on the Pt sites.This work provides valuable guidance for future optimization of hydrogen quality and also emphasizes the importance of anti-poisoning anode catalyst development,especially towards H_(2)S impurities that seriously affect the durability of PEMFCs.

Supercritical water oxidation of polyvinyl alcohol and desizing wastewater: Influence of NaOH on the organic decomposition

Polyvinyl alcohol is a refractory compound widely used in industry. Here we report supercritical water oxidation of polyvinyl alcohol solution and desizing wastewater with and without sodium hydroxide addition. However, it is difficult to implement complete degradation of organics even though polyvinyl alcohol can readily crack under supercritical water treatment. Sodium hydroxide had a significant catalytic effect during the supercritical water oxidation of polyvinyl alcohol. It appears that the OH ion participated in the C-C bond cleavage of polyvinyl alcohol molecules, the CO2-capture reaction and the neutralization of intermediate organic acids, promoting the overall reactions moving in the forward direction. Acetaldehyde was a typical intermediate product during reaction. For supercritical water oxidation of desizing wastewater, a high destruction rate （98.25%） based on total organic carbon was achieved. In addition, cases where initial wastewater was alkaline were favorable for supercritical water oxidation treatment, but salt precipitation and blockage issues arising during the process need to be taken into account seriously.

Influence factors for the oxidation of pyrite by oxygen and birnessite in aqueous systems

The oxidation of exposed pyrite causes acid mine drainage, soil acidification, and the release of toxic metal ions. As the important abiotic oxidants in supergene environments,oxygen and manganese oxides participate in the oxidation of pyrite. In this work, the oxidation processes of natural pyrite by oxygen and birnessite were studied in simulated systems, and the influence of p H, Fe（II） and Cr（III） on the intermediates and redox rate was investigated. SO42-and elemental S were formed as the major and minor products,respectively, during the oxidation processes. Ferric（hydr） oxides including Fe（OH）3and goethite were formed with low degree of crystallinity. Low p H and long-term reaction facilitated the formation of goethite and ferric hydroxide, respectively. The rate of pyrite oxidation by birnessite was enhanced in the presence of air（oxygen）, and Fe（II） ions played a key role in the redox process. The addition of Fe（II） ions to the reaction system significantly enhanced the oxidation rate of pyrite; however, the presence of Cr（III） ions remarkably decreased the pyrite oxidation rate in aqueous systems. The introduction of Fe（II） ions to form a Fe（III）/Fe（II） redox couple facilitated the electron transfer and accelerated the oxidation rate of pyrite. The present work suggests that isolation from air and decreasing the concentration of Fe（II） ions in aqueous solutions might be effective strategies to reduce the oxidation rate of pyrite in mining soils.

Direct synthesis of nitriles by Cu/DMEDA/TEMPO-catalyzed aerobic oxidation of primary amines with air

By screening the copper catalysts,ligands,and the reaction conditions,a simple CuCl/DMEDA/TEMPO catalyst system readily available from commercial sources is developed for a direct and selective synthesis of the useful nitriles by an aerobic oxidation reaction of primary amines using air as an advantageous oxidant under mild conditions.

Conversion of the refractory ammonia and acetic acid in catalytic wet air oxidation of animal byproducts

Wet air oxidation （WAO） and catalytic wet air oxidation （CWAO） of slaughtered animal byproducts （ABPs） were investigated. Two step experiment was carried out consisting of a non-catalysed WAO run followed by a CWAO run at 170-275 ℃, 20 MPa, and reaction time 180 min. The WAO （lst step） of sample （5 g/L total organic carbon （TOC）） yielded （82.0 ±4）% TOC removal and （78.4 ± 13.2）% conversion of the initial organic-N into NH4＋-N. Four metal catalysts （Pd, Pt, Rh, Ru） supported over alumina have been tested in catalytic WAO （2nd step） at elevated pH to enhance ammonia conversion and organic matter removal, particularly acetic acid. It was found that the catalysts Ru, Pt, and Rh had significant effects on the TOC removal （95.1%, 99.5% and 96.7%, respectively） and on the abatement of ammonia （93.4%, 96.7% and 96.3%, respectively） with high nitrogen selectivity. The catalyst Pd was found to have the less activity while Pt had the best performance. The X-Ray diffraction analysis showed that the support of catalyst was not stable under the experimental conditions since it reacted with phosphate present in solution. Nitrite and nitrate ions were monitored during the oxidation reaction and it was concluded that CWAO of ammonia in real waste treatment framework was in good agreement with the results obtained from the literature for ideal solutions of ammonia.

Recent advances in inkjet printing synthesis of functional metal oxides

lnkjet printing （IJP） synthesis has emerged as a useful technique for the fabrication of functional metal oxides in the fields of nanotechnology and materials science. In this paper, we will review the fundamental state-of-the-art principles of the special ink formulations used for IJP synthesis of functional metal oxides and the applications of these oxides.

Monodispersed Pt nanoparticles on reduced graphene oxide by a non-noble metal sacrificial approach for hydrolytic dehydrogenation of ammonia borane

Downsizing noble metal nanoparticles,such as Pt,is an essential goal for many catalytic reactions.A non-noble metal sacrificial approach was used to immobilize monodispersed Pt nanoparticles （NPs） with a mean size of 1.2 nm on reduced graphene oxide （RGO）.ZnO co-precipitated with Pt NPs and subsequently sacrificed by acid etching impedes the diffusion of Pt atoms onto the primary Pt particles and also their aggregation during the reduction of precursors.The resulting ultrafine Pt nanoparticles exhibit high activity （a turnover frequency of 284 min-1 at 298 K） in the hydrolytic dehydrogenation of ammonia borane.The non-noble metal sacrificial approach is demonstrated as a general approach to synthesize well-dispersed noble metal NPs for catalysis.

A convenient catalytic oxidative 1,2-shift of arylalkenes for preparation of α-aryl ketones mediated by NaI

Using a catalytic amount of Nal and a stoichiometric oxidant Oxone-@,a convenient procedure has been developed for the catalytic oxidative 1,2-shift of arylalkenes in CH3CN/H2O at room temperature,which provides the corresponding α-aryl ketones in moderate to good yields.In this protocol,sodium iodide is first oxidized into hypoiodous acid,which reacts with arylalkene to afford iodohydrin.Then,the iodohydrin is transformed into the α-aryl ketone via an oxidative 1,2-shift rearrangement.