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Bismuth vanadate (BiVO4) as an outstanding semiconductor material has been extensively used in visible-light-driven photocatalytic oxidation. However, the fast electron-hole recombination on the surface of BiVO4 photoanode impairs its photoelectrochemical oxidation performance. In this work, we demonstrate, for the first time, that a cobalt-polyoxometalate (Ag10[Co4(H2O)2(PW9O34)2], PW9Co) is exploited as a hole extraction layer on the surface of BiVO4 photoanode for boosting photoelectrochemical activity by promoting hole extraction and transfer. Compared to the pure BiVO4 photoanode, the PW9Co-modified BiVO4 photoanode in photoelectrochemical water oxidation reaction exhibited a higher photocurrent density of 3.06 mA cm−2 at 1.23 V vs. RHE under AM 1.5G illumination, achieving a 3.3-fold improvement in photocurrent density. Furthermore, we performed a photoelectrochemical reaction of oxidizing benzyl alcohol into benzaldehyde, in which the reaction yield of using the modified BiVO4 photoanode is significantly superior to the pure BiVO4 photoanode. These results prove that a rational selection of cobalt-polyoxometalate as a hole extraction layer can efficiently enhance the photoelectrochemical oxidation activity of BiVO4 photoanode.

An X-band transverse-deflecting structure is a crucial RF unit for bunch-length measurement conducted at the Shanghai Soft-X-ray Free Electron Laser Facility (SXFEL) at the Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences. The target of this prototype deflector is to operate at 30 MW to have a deflection of 10 MV/structure to realize 20-fs resolution in a full-size structure (0.6 meters long, used on user facility of SXFEL), which satisfies the requirement of the linac beam size measurement at 840 MeV. The program was started in 2010 focusing on X-band deflectors, including design, fabrication, and RF measurement. The electrical tuning of the deflector was successfully done using a unique “cage”-type bead. Recently, a high-power test was conducted at KEK on the first prototype deflector. The high-gradient features at the nominal gradient was proven, but the further increase of power and pulse width was limited at 45 MW with a 173-ns pulse width due to approaching the feasible limit of the modified pointing vector value 5 MW/mm2. In this final stage, frequent breakdowns near the badly brazed point occurred and further conditioning had to be suspended owing to limited available time.

Three-dimensional hierarchical nanoflowers self-assembled with the orthorhombic molybdenum oxide (α-MoO3) nanoflowers were synthesized by the modified hydrothermal method. The structure characterizations of the three-dimensional α-MoO3 nanoflowers were carried out by scanning electron microscope (SEM), Energy Disperse Spectroscopy (EDS), X-ray diffraction (XRD) and nitrogen adsorption-desorption measurement. Moreover, the three-dimensional α-MoO3 nanoflowers as photocatalyst exhibited enhanced photocatalytic activity towards photodegradation of Rhodamine B (RhB) under xenon (Xe) lamp irradiation. The results of SEM, EDS, XRD and nitrogen adsorption-desorption measurement showed the three-dimensional α-MoO3 nanoflowers have a better morphology, pore size (7.99 nm) and surface areas (50.788 m2 g−1) than hexagonal MoO3 (h-MoO3) nanosheets, photocatalytic activity studies confirmed that the three-dimensional α-MoO3 nanoflowers photocatalyst exhibits a high visible-light-driven activity for photodegradation of RhB solution of 91.57% within 160 min under Xe lamp irradiation. A mechanism was also proposed for the degradation of RhB by three-dimensional α-MoO3 nanoflowers.

An ultrafast electron diffraction (UED) facility is located at Shanghai Jiao Tong University. The layout of the UED is divided into two modules. The accelerating module has one S-band photocathode RF gun, one C-band harmonic buncher, and one C-band deflector. The power-generating module has one S-band klystron and one C-band klystron. To meet the high-precision requirements, a MicroTCA.4-based low level radio frequency (LLRF) system is used to provide a stable RF field in the cavities. In this paper, we introduce the RF distributions, LLRF system, firmware and software of the feedback controller, and field stability of the RF gun; and present an analysis of the measurement results for UED.

An X-band high gradient accelerating structure is a challenging technology for implementation in advanced electron linear accelerator facilities. The present work discusses the design of an X-band accelerating structure for dedicated application to a compact hard X-ray free electron laser facility at the Shanghai Institute of Applied Physics, and numerous design optimizations are conducted with consideration for radio frequency (RF) breakdown, RF efficiency, short-range wakefields, and dipole/quadrupole field modes, to ensure good beam quality and a high accelerating gradient. The designed X-band accelerating structure is a constant gradient structure with a 4π/5 operating mode and input and output dual-feed couplers in a racetrack shape. The design process employs a newly developed effective optimization procedure for optimization of the X-band accelerating structure. In addition, the specific design of couplers providing high beam quality by eliminating dipole field components and reducing quadrupole field components is discussed in detail.

A tuning method augmented by the bead-pull technique based on nonresonant perturbation field distribution measurements has been widely applied for traveling-wave (TW) accelerating structures. The method is also suitable for deflecting structures, but some key considerations of the field components of the HEM 11 mode and the selection of bead merit discussion. A “cage”-type perturbing object has been designed, fabricated and applied in nonresonant perturbation measurements. Measurements on an S-band TW deflecting structure are carried out, and the measurement and tuning method will be used on the newly developed X-band deflecting structure at Shanghai Institute of Applied Physics.

A serial of CdS/POM (POM denotes polyoxometalate: P2MoxW18-x, x = 3, 9, 15) nanospheres were fabricated through electrostatic self-assembly method. For the first time, the semiconductor properties of the three polyoxometalates were investigated to direct the rational design of the type-II heterojunction photocatalysts. The morphology and semiconducting properties of the as-prepared materials were characterized by using X-ray powder diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectra, Mott-Schottky plots, surface photovoltage spectroscopy and time-resolved photocurrent curves. The band gap of P2Mo3W15, P2Mo9W9 and P2Mo15W3 is taken respectively to be 2.34 eV, 2.26 eV and 2.15 eV. The average diameters of CdS and CdS/P2MoxW18-x (X = 3, 9, 15) nanospheres are all around 80–100 nm, and CdS/P2MoxW18-x (X = 3, 9, 15) nanospheres have better photoelectric performance than pure CdS. The formation of type II heterostructure between CdS and P2MoxW18-x could promote the separation and transfer of photoinduced electron-hole pairs, so the photocatalytic activities of CdS/POM nanospheres for Cr(VI) reduction were improved significantly. Among them, the CdS/P2Mo15W3 photocatalyst exhibited the highest photocatalytic yield of 64% for the Cr(VI) removal. Our study provides new insight into developing novel CdS/P2MoxW18-x nanocomposite photocatalysts for environmental applications.

C-band RF acceleration is a crucial technology for the compact Free Electron Laser (FEL) facility at the Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences. A project focusing on C-band RF acceleration technology was launched in 2008, based on high-gradient accelerating structures powered by klystron and pulse compressor units. The target accelerating gradient is 40 MV/m or higher. Recently one prototype of C-band RF unit, consisting of a 1.8 m accelerating structure and a klystron with a TE0115 mode pulse compressor, has been tested with high-power and electron beam. Stable operation at 40 MV/m was demonstrated and, 50 MV/m approached by the end of the test. This paper introduces the C-band R&D program at SINAP and presents the experiment results of high-power and beam tests.

Modification of semiconductor materials by polyoxometalates (POMs) is a promising strategy for increasing their photoelectrocatalytic (PEC) activity. In this work, we synthesized POM-modified CdS composite nanocrystals based on three kinds of Keggin-type mixed-addendum Mo/W POMs (Ag3PMo3W9O40, Ag3PMo6W6O40, and Ag3PMo9W3O40). This is the first report on the semiconductor properties of the three Keggin-type mixed-addendum Mo/W POMs. Their PEC performances were studied by transient photocurrent responses, electrochemical impedance spectroscopy, and PEC oxidation of As(III) to As(V). The PEC performances of POM-modified CdS composite nanocrystals (CdS/Ag3PMo3W9O40, CdS/Ag3PMo6W6O40, and CdS/Ag3PMo9W3O40) were superior to the performance of pure CdS nanocrystals. CdS/Ag3PMo3W9O40 composite nanocrystals exhibited the highest efficiency for the PEC oxidation of As(III) to As(V), which was about 85% higher than that of the pure CdS nanocrystals. The present study provides insight into developing novel composite nanocrystals with Keggin-type mixed Mo/W POMs for efficient PEC oxidation.

Full utilization of the incident light is an effective strategy to enhance photovoltaic performance of perovskite solar cells (PSCs). Here, we used lanthanide-containing polyoxometalate Na9[EuW10O36] (EuW10) as a luminescent down-conversion material incorporated in mesoporous TiO2 layer for boosting the power conversion efficiency (PCE) of the printable hole transport material-free PSCs. The EuW10 can convert the high energy photons into the low energy visible photons matched well with the absorption of perovskite, so that photogenerated current carriers increase substantially. This research represents the first example of using lanthanide-containing polyoxometalate as down-conversion materials to effectively improve PCE in solar cells. Compared with pristine TiO2 based PSCs, the EuW10-TiO2 based PSCs showed an enhanced power conversion efficiency (PCE) from 11.42% to 14.36% and obtained a remarkable photocurrent density of 23.46 mA/cm2. Besides, the EuW10-TiO2 based device exhibited a better long-term stability, which could maintain 98% initial efficiency after storage for 14 days. Since the efficiency of the printable perovskite solar cells has been a key factor to achieve commercial implementations, we consider that the results from this work demonstrate a new kind of down-conversion materials to boost PCE and stability.