Recent developments in visible-light photocatalytic degradation of antibiotics

With the significant discharge of antibiotic wastewater into the aquatic and terrestrial ecosystems, antibiotic pollution has become a serious problem and presents a hazardous risk to the environment. To address such issues, various investigations on the removal of antibiotics have been undertaken. Photocatalysis has received tremendous attention owing to its great potential in removing antibiotics from aqueous solutions via a green, economic, and effective process. However, such a technology employing traditional photocatalysts suffers from major drawbacks such as light absorption being restricted to the UV spectrum only and fast charge recombination. To overcome these issues, considerable effort has been directed towards the development of advanced visible light-driven photocatalysts. This mini review summarises recent research progress in the state-of-the-art design and fabrication of photocatalysts with visible-light response for photocatalytic degradation of antibiotic wastewater. Such design strategies involve the doping of metal and non-metal into ultraviolet light-driven photocatalysts, development of new semiconductor photocatalysts, construction of heterojunction photocatalysts, and fabrication of surface plasmon resonance-enhanced photocatalytic systems. Additionally, some perspectives on the challenges and future developments in the area of photocatalytic degradation of antibiotics are provided.

二氧化氯的生产方法

本发明涉及一种二氧化氯的生产方法。该法是在质子催化剂强无机酸水溶液存在下，搅拌并将氯酸和过氧化氢同时加到质子催化剂强无机酸水溶液中，在30－95℃的温度下，使氯酸与过氧化氢反应生成二氧化氯。其反应速率高，转化率高，仅生成二氧化氯、氧和水，没有氯气生成。质子催化剂可循环使用，无废液废渣排出，又可适用于各种生产方式，工艺装置简单，操作方便，生产安全，且生产成本低。

甲基葡萄糖苷的合成工艺改进

甲基葡萄糖苷的合成为无水操作，工艺过程中用到的酸催化剂造价高，来源窄，使应用受到了很大的限制，本实验尝试采用廉价易得的氯化氢为质子酸催化剂，无水条件下加入氯化氢，取得了良好的效果，同时对催化剂的用量和后处理等因素进行了初步探索研究，结论是葡萄糖：催化剂：1：0．01时，产物收率达91．1％

Single-step conversion of lignin monomers to phenol: Bridging the gap between lignin and high-value chemicals

Transformation of lignin into high-value chemicals is hampered by the complexity of monomers obtained from lignin depolymerization. Here we report a strategy, composed of hy-dro-demethoxylation and de-alkylation reactions, that is able to chemically converge various lig-nin-derived phenolic monomers into phenol in a single-step. Using 2-methoxy-4-propylphenol as a model compound, Pt/C exhibited the best performance in hydro-demethoxylation reaction afford-ing 80% 4-propylphenol from 2-methoxy-4-propylphenol, while H-ZSM-5 was identified as the most suitable catalyst for de-alkylation, achieving 83% yield of phenol from 4-propylphenol. Since the two catalysts operate under compatible conditions, combining the two catalysts to simultane-ously promote both hydro-demethoxylation and de-alkylation reactions was achieved. Configura-tion of how to organize the catalysts is a critical parameter, where the physical mixture of the two was most effective, providing over 60% phenol from 2-methoxy-4-propylphenol in a single-step.

An effective FeCl_3 template assisted synthesis of nitrogen, sulfur and iron-tridoped carbon nanosheets from a protic salt for oxygen reduction electrocatalysis

Doping heteroatoms into carbon matrix was an efficient strategy to achieve a high-performance non-precious metal oxygen reduction electrocatalyst. Herein, an in situ templated synthesis strategy has been demonstrated to fabricate nitrogen, sulfur and iron-tridoped mesoporous carbon nanosheets（NSFC） with FeCl3 as the two-dimensional template. And a protic salt was used as the carbon, nitrogen and sulfur source, which realized one-step preparation of catalyst materials and the co-doping of various heteroatoms simultaneously. As a result, the optimized NSFC catalyst possessed comparable catalytic activity and selectivity, while superior durability and methanol permeability resistance to commercial 30 wt% Pt/C catalyst in alkaline media. Such excellent performance should be ascribed to the efficient multiple-element doping into the large-specific-surface-area and highly stable carbon nanosheets realized by the in situ synthesis route with a novel FeCl3 template.

Interatomic diffusion in Pd-Pt core-shell nanoparticles

Pt monolayer-based core-shell catalysts have garnered significant interest for the application of low temperature fuel cell technology as their use may enable a decreased loading of Pt while still providing sufficient current density to meet volumetric requirements. One promising candidate in this class of materials is a Pd@Pt core-shell catalyst, which shows enhanced activity toward oxygen reduction reaction(ORR). One concern with the use of Pd@Pt, however, is the durability of the core-shell structure as Pd atoms are thermodynamically favored to migrate to the surface. The pathway of the migration has not been systematically studied. The current study explores the stability of this structure to thermal annealing and probes the effect of this heat treatment on the catalyst surface structure and its oxygen reduction activity. It was found that surface alloying between Pd and Pt occurs at temperatures as low as 200 °C, and significantly alters the structure and ORR catalytic activity in the range of 200–300 °C. Our results shed lights on the thermal induced interatomic diffusion in all core-shell and thin film structures.

Recent developments of nanocarbon based supports for PEMFCs electrocatalysts

Nanocarbons,widely and commonly used as supports for supported Pt-based electrocatalysts in PEMFCs,play a significant role in Pt dispersion and accessibility,further determining their corresponding electrocatalytic performance.This paper provides an overview of the nanoarchitectures and surface physicochemical properties of nanocarbons affecting the electrocatalyst performance,with an emphasis on both physical characteristics,including pore structure,and chemical properties,including heteroatom doping and functional carbon-based supports.This review discusses the recent progress in nanocarbon supports,guides the future development direction of PEMFC supports,and provides our own viewpoints for the future research and design of PEMFCs catalysts,advancing the commercialization of PEMFCs.

Fe,N,S-doped porous carbon as oxygen reduction reaction catalyst in acidic medium with high activity and durability synthesized using CaCl_2 as template

Proton exchange membrane fuel cells suffer from the sluggish kinetics of the oxygen reduction reaction(ORR)and the high cost of Pt catalysts.In the present work,a high‐performance ORR catalystbased on Fe,N,S‐doped porous carbon(FeNS‐PC)was synthesized using melamine formaldehyderesin as C and N precursors,Fe(SCN)3as Fe and S precursors,and CaCl2as a template via a two‐stepheat treatment without a harsh template removal step.The results show that the catalyst treated at900℃(FeNS‐PC‐900)had a high surface area of775m2/g,a high mass activity of10.2A/g in anacidic medium,and excellent durability;the half‐wave potential decreased by only20mV after10000potential cycles.The FeNS‐PC‐900catalyst was used as the cathode in a proton exchangemembrane fuel cell and delivered a peak power density of0.49W/cm2.FeNS‐PC‐900therefore hasgood potential for use in practical applications.

Pd catalysts supported on rGO-TiO_2 composites for direct synthesis of H_2O_2: Modification of Pd^(2+)/Pd^0 ratio and hydrophilic property

The use of nanostructured composites as catalyst supports is a promising route to prepare catalysts with high selectivity and productivity. In this work, reduced graphene oxide-TiO_2(rGP-x) composites with a variation of reduced graphene oxide(rGO) content were synthesized by hydrothermal method. Pd/rGP-x catalysts were prepared in incipient-wetness impregnation method for the direct synthesis of H_2O_2 from H2 and O_2. The morphology and electronic properties of catalysts were investigated by XPS, TEM, and Raman spectroscopy.The ratio of Pd^(2+)/Pd^0 and the hydrophobicity of the catalysts were increased with the rising content of rGO. As the amount of rGO in the catalysts varied in the range of 0.025 wt%–2 wt%, the selectivity of H_2O_2 exhibited a tendency of increasing firstly and then decreasing from 0.1 wt% to 2 wt%. It indicates that good catalytic performance for H_2O_2 synthesis can be achieved only when appropriate amount of rGO is introduced. The H_2O_2 selectivity and productivity of Pd/r GP-0.025 both improved remarkably compared with Pd/P25. This enhancement originated from the combined effects of the proper ratio of Pd^(2+)/Pd^0 and hydrophobicity of the catalyst.

Multimetallic AuPd@Pd@Pt core-interlayer-shell icosahedral electrocatalysts for highly efficient oxygen reduction reaction

Incorporating Pt with core metals into Pt-based core-shell catalysts is regarded as a promising strategy to substantially enhance the catalytic properties towards oxygen reduction reaction(ORR) in fuel cells due to the synergetic effect between distinct metals. In this wok, ultrathin Pt skins with two atomic layers were epitaxially coated on as-prepared icosahedral Au_50Pd_50, Au_60Pd_40 and Au_66Pd_34 nanocrystal seeds,which are constructed with alloyed cores and Pd shells with different thickness. Through electron microscopic characterizations, Pd interlayers with tunable thickness of 3, 6, and 12 atomic layers can be found in the Au_66Pd_34@Pt, Au_60 Pd_40@Pt and Au_50Pd_50@Pt icosahedra, respectively. These icosahedral Au Pd@Pd@Pt nanocrystals show substantially enhanced activities and durabilities in electrocatalytic measurements towards ORR compared to Au_75Pd_25@Pt icosahedra without Pd interlayer and commercial Pt/C catalysts. Specifically, Au_60Pd_40@Pt icosahedra with 6 atomically thick Pd interlayer display the best electrocatalytic performances, whose mass activities before and after durability tests of 50,000 cycles are11.6 and 30.2 times, respectively, as high as that of the commercial Pt/C.

A DFT study on PtMo resistance to SO_2 poisoning

Pt is a catalyst in proton exchange membrane fuel cell （PEMFC）, and its activity will be degraded in the air due to the exist- ence of SOx impurities. On strategy is introducing of Mo into the Pt catalyst because it can improve the SOx-tolerance capacity. Based on the aforementioned phenomenon, a density function theory （DFT） study on SOx adsorbed on Pt（111） and PtMo（111） was performed to enhance Pt catalytic activity. The adsorption energy of adsorbed species, the net change, partial density of state （PDOS）, and d-band center were calculated and analyzed comparatively. The results show that the presence of Mo-atom weakens the S-Pt bond strength and reduces the adsorption energies for SO2, S and SO3 on PtMo（111）. Moreover, the Mo atom weakens the effects of SO2 on the PtMo（lll） electronic structure and makes the catalyst maintains its original electronic structure after SO2 adsorption as compared with Pt（111）.

Highly dispersed Pt species anchored on W_(18)O_(49)nanowires mediate efficient and durable hydrogen evolution in acidic water

Platinum-based material is the most efficient and durable electrocatalyst for motivating the hydrogen evolution reaction(HER)in an acidic electrolyte;however,its low abundance and high cost limit its further application in proton-exchange membrane water electrolysis(PEMWE)technology.Therefore,minimizing the Pt amount while retaining high activity would be desirable.Herein,we use defect-rich W_(18)O_(49)nanowires to anchor well-dispersed,ultrafine Pt species(Pt-W_(18)O_(49))via a freeze-drying method to avoid aggregation,further mediating an efficient and durable HER in acidic water.Density functional theory analyses also demonstrate that the strong electronic interaction between the Pt species and W_(18)O_(49)support greatly improves the HER performance.With a 1/10 Pt loading amount of the commercial 20 wt%Pt/C,the Pt-W_(18)O_(49)catalyst requires the overpotentials of 116 and 743 mV to achieve high current densities of 100 and 1000 mA cm^(−2)in 0.5 mol L^(−1)H_(2)SO_(4),outperforming those of the 20 wt%Pt/C benchmark.More importantly,the Pt-W_(18)O_(49)catalyst can sustain a high-currentdensity HER at 500 mA cm^(−2)for more than 38 h without obvious degradation.This work paves a new avenue for synergistically reducing the Pt amount and retaining high activity for real-world PEMWE.

Enhanced stability of Pt nanoparticle electrocatalysts for fuel cells

Although polymer electrolyte membrane fuel cells （PEMFCs） have received broad attention due to their virtually zero emission, high power density, and high efficiency, at present the limited stability of the electrocatalysts used in PEMFCs is a critical limitation to their large-scale commercialization. As a type of popularly used electrocatalyst material, carbon black supported platinum （Pt/C）--although highly efficient--undergoes corrosion of carbon, Pt dissolution, Ostwald ripening, and aggregation of Pt nanoparticles （NPs） under harsh chemical and electro- chemical oxidation conditions, which results in performance degradation of the electrocatalysts. In order to overcome these disadvantages, many groups have tried to improve the carbon support materials on which Pt is loaded. It has been found that some novel carbon nanomaterials and noncarbon materials with high surface areas, sufficient anchoring sites, high electrical conductivities, and high oxidation resistance under the strongly oxidizing condition in PEMFCs are ideal alternative supports. This review highlights the following aspects： （i） Recent advances in using novel carbon nanomaterials and noncarbon support materials to enhance the long-term durability of electrocatalysts; （ii） solutions to improve the electrical conductivity, surface area, and the strong interaction between metal and supports; and （iii） the synergistic effects in hybrid supports which help improve the stability of electrocatalysts.

SC-IrO_2 NR-carbon hybrid:A catalyst with high electrochemical stability for oxygen reduction

The enhanced electrochemical stability of the synthesized hybrid catalyst has been demonstrated by the introduction of the synergistic effect between carbon powder additive and the prepared catalyst.Single crystal IrO 2 nanorod (SC-IrO 2 NR) catalyst was prepared by a sol-gel method.The structure and performance of the catalyst sample were characterized by X-ray diffraction spectroscopy (XRD),scanning electron microscope (SEM),transmission electron microscope (TEM),rotating disk electrode (RDE) and cyclic voltammetry (CV) measurements.XRD patterns and TEM images indicate that the catalyst sample has a rutile IrO 2 single crystal nanorod structure.The onset potential for oxygen reduction reaction (ORR) of the SC-IrO 2 NR-carbon hybrid catalyst specimen is 0.75 V (vs.RHE) in RDE measurement.CV and RDE test results show that the SC-IrO 2 NR-carbon hybrid catalyst has a better electrochemical stability in comparison with the commercial Pt/C catalyst,with attenuation ratios of 17.67% and 44.60% for the SC-IrO 2 NR-carbon hybrid catalyst and the commercial Pt/C catalyst after 1500 cycles,respectively.Therefore,in terms of stability,the SC-IrO 2 NR-carbon hybrid catalyst has a promising potential in the application of the proton exchange membrane fuel cell.

Characterization of different plasma-treated cobalt oxide catalysts for oxygen reduction reaction in alkaline media

Plasma-synthesized cobalt oxide supported on carbon has been analyzed for its use for electrocatalytic oxygen reduction reaction （ORR） in alkaline anion exchange membrane fuel cells （AEMFC）. This work presents the ORR activity in 0.1 mol L-1 KOH and 0.1 tool L-1 K2CO3 at 25 ℃. Cyclic voltammetry （CV） was used to determine the potentials at which the ORR occurs and to evaluate the stability of catalyst. Moreover, a rotating ring-disk electrode （RRDE） was used to investigate the activity of the catalysts and the formation of the by-product hydroperoxide anion （HO2-） as well as to identify the preferred pathway of the ORR. Calculated kinetic parameters for the ORR for the cobalt catalysts are shown in this work together with a comparison to a commercial platinum catalyst. However, the cobalt oxide produced more by-products which could lead to damage of the membrane in a fuel cell through a radical attack of the polymer backbone.