Liaoyong Wen

Photoelectrodes based upon Mo:BiVO4 inverse opals for photoelectrochemical water splitting.

BiVO4 has been regarded as a promising material for photoelectrochemical water splitting, but it suffers from a major challenge on charge collection and utilization. In order to meet this challenge, we design a nanoengineered three-dimensional (3D) ordered macro-mesoporous architecture (a kind of inverse opal) of Mo:BiVO4 through a controllable colloidal crystal template method with the help of a sandwich solution infiltration method and adjustable post-heating time. Within expectation, a superior photocurrent density is achieved in return for this design. This enhancement originates primarily from effective charge collection and utilization according to the analysis of electrochemical impedance spectroscopy and so on. All the results highlight the great significance of the 3D ordered macro-mesoporous architecture as a promising photoelectrode model for the application in solar conversion. The cooperating amplification effects of nanoengineering from composition regulation and morphology innovation are helpful for creating more purpose-designed photoelectrodes with highly efficient performance.

Large-scale highly ordered Sb nanorod array anodes with high capacity and rate capability for sodium-ion batteries

Na-ion batteries are a potential substitute to Li-ion batteries for energy storage devices. However, their poor electrochemical performance, especially capacity and rate capability, is the major bottleneck to future development. Here we propose a performance-oriented electrode structure, which is 1D nanostructure arrays with large-scale high ordering, good vertical alignment, and large interval spacing. Benefiting from these structural merits, a great enhancement in electrochemical performance could be achieved. Taking Sb as an example, we firstly report large-scale highly ordered Sb nanorod arrays with uniform large interval spacing (190 nm). In return for this electrode design, high ion accessibility, fast electron transport, and strong electrode integrity are presented here. Used as additive- and binder-free anodes for Na-ion batteries, Sb nanorod arrays showed a high capacity of 620 mA h g−1 at the 100th cycle with a retention of 84% up to 250 cycles at 0.2 A g−1, and a superior rate capability for delivering reversible capacities of 579.7 and 557.7 mA h g−1 at 10 and 20 A g−1, respectively. A full cell coupled by a P2-Na2/3Ni1/3Mn2/3O2 cathode and a Sb nanorod array anode was also constructed, which showed good cycle performance up to 250 cycles, high rate capability up to 20 A g−1, and large energy density up to 130 Wh kg−1. These excellent electrochemical performances shall pave the way for developing more applications of Sb nanorod arrays in energy storage devices.

Ultrathin alumina membranes for surface nanopatterning in fabricating quantum-sized nanodots.

Using ultrathin alumina membranes (UTAMs) as evaporation or etching masks large-scale ordered arrays of surface nanostructures can be synthesized on substrates. However, it is a challenge for this technique to synthesize quantum-sized surface structures. Here an innovative approach to prepare UTAMs with regularly arrayed pores in the quantum size range is reported. This new approach is based on a well-controlled pore-opening process and a modulated anodization process. Using UTAMs with quantum-sized pores for the surface patterning process, ordered arrays of quantum dots are synthesized on silicon substrates. This is the first time in realizing large-scale regularly arrayed surface structures in the quantum size range using the UTAM technique, which is an important breakthrough in the field of surface nanopatterning.

Cost-effective atomic layer deposition synthesis of Pt nanotube arrays: application for high performance supercapacitor.

Due to the unique advantages of Pt, it plays an important role in fuel cells and microelectronics. Considering the fact that Pt is an expensive metal, a major challenging point nowadays is how to realize efficient utilization of Pt. In this paper, a cost-effective atomic layer deposition (ALD) process with a low N2 filling step is introduced for realizing well-defined Pt nanotube arrays in anodic alumina nano-porous templates. Compared to the conventional ALD growth of Pt, much fewer ALD cycles and a shorter precursor pulsing time are required, which originates from the low N2 filling step. To achieve similar Pt nanotubes, about half cycles and 10% Pt precursor pulsing time is needed using our ALD process. Meanwhile, the Pt nanotube array is explored as a current collector for supercapacitors based on core/shell Pt/MnO2 nanotubes. This nanotube-based electrode exhibits high gravimetric and areal specific capacitance (810 Fg(-1) and 75 mF cm(-2) at a scan rate of 5 mV s(-1) ) as well as an excellent rate capability (68% capacitance retention from 2 to 100 Ag(-1) ). Additionally, a negligible capacitance loss is observed after 8000 cycles of random charging-discharging from 2 to 100 Ag(-1) .

Designing Heterogeneous 1D Nanostructure Arrays Based on AAO Templates for Energy Applications.

In order to fulfill the multiple requirements for energy production, storage, and utilization in the future, the conventional planar configuration of current energy conversion/storage devices has to be reformed, since technological evolution has promoted the efficiency of the corresponding devices to be close to the theoretical values. One promising strategy is to construct multifunctional 1D nanostructure arrays to replace their planar counterparts for device fabrication, ascribing to the significant superiorities of such 1D nanostructure arrays. In the last three decades, technologies based on anodic aluminium oxide (AAO) templates have turned out to be valuable meaning for the realization of 1D nanostructures and have attracted tremendous interest. In this review, recent progress in energy-related devices equipped with heterogeneous 1D nanostructure arrays that fabricated through the assistance of AAO templates is highlighted. Particular emphasis is given on how to develop efficient devices via optimizing the componential and morphological parameters of the 1D nanostructure arrays. Finally, aspects relevant to the further improvement of device performance are discussed.

Multiple nanostructures based on anodized aluminium oxide templates

Several physico-chemical effects and properties in the solid state involve nanoscale interactions between adjacent materials and morphologies. Arrays of binary nanostructures can generate intimate interactions between different sub-components, but fabricating binary nanostructures is challenging. Here, we propose a concept to achieve diverse binary nanostructure arrays with high degrees of controllability for each of the sub-components, including material, dimension and morphology. This binary nanostructuring concept originates with a distinctive binary-pore anodized aluminium oxide template that includes two dissimilar sets of pores in one matrix, where the openings of the two sets of pores are towards opposite sides of the template. Using the same growth mechanism, the binary-pore template can be extended to multi-pore templates with more geometrical options. We also present photoelectrodes, transistors and plasmonic devices made with our binary nanostructure arrays using different combination of materials and morphologies, and demonstrate superior performances compared to their single-component counterparts.

Manipulation of charge transfer and transport in plasmonic-ferroelectric hybrids for photoelectrochemical applications

Utilizing plasmonic nanostructures for efficient and flexible conversion of solar energy into electricity or fuel presents a new paradigm in photovoltaics and photoelectrochemistry research. In a conventional photoelectrochemical cell, consisting of a plasmonic structure in contact with a semiconductor, the type of photoelectrochemical reaction is determined by the band bending at the semiconductor/electrolyte interface. The nature of the reaction is thus hard to tune. Here instead of using a semiconductor, we employed a ferroelectric material, Pb(Zr,Ti)O3 (PZT). By depositing gold nanoparticle arrays and PZT films on ITO substrates, and studying the photocurrent as well as the femtosecond transient absorbance in different configurations, we demonstrate an effective charge transfer between the nanoparticle array and PZT. Most importantly, we show that the photocurrent can be tuned by nearly an order of magnitude when changing the ferroelectric polarization in PZT, demonstrating a versatile and tunable system for energy harvesting.

Fabrication and characterization of well-aligned, high density ZnO nanowire arrays and their realizations in Schottky device applications using a two-step approach

We report a two-step general and viable approach for preparing a large area of high density and horizontally well-aligned arrays of zinc oxide nanowires (ZnO NWs) for the realization of Schottky device applications on inexpensive, flexible polymer substrate. A modified chemical vapor deposition (CVD) process is initially used for synthesizing the highly efficient and rapid growth of vertical ZnO NW arrays along their [0001] direction, which is perpendicular to the donor substrate surface without using any metal catalyze. This is followed by transferring the NWs to a receiver substrate by a dry contact printing method. Utilizing the ZnO NWs synthesized by our method, a fully controllable and relatively large separation between the adjacent rows of silver (Ag) electrodes for the electrical contact with the NWs can be obtained using a photolithographic process. The printed ZnO NWs are well aligned along their c-axis, resulting in a spontaneous polarization which leads to a potential gradient along the length of the individual NW. This coupled with the effect of the surface states in the ZnO NWs result in the formation of a Schottky contact at the Ag/ZnO NW interface. Hence, virtually all of the ZnO NW arrays are functional as Schottky diodes which display non-linear current–voltage characteristics with good rectifying diode-like behaviour.

p-Type CuBi2O4: an easily accessible photocathodic material for high-efficiency water splitting

In view of the disadvantages of the conventional photocathodic materials, we focus on exploiting new candidates for a high-efficiency photoelectrochemical (PEC) system. Herein, we report on the fabrication of CuBi2O4 (CBO) films on FTO (fluorine doped tin oxide) and FTO/Au substrates, respectively, through the electrochemical deposition approach. It was observed that the presence of a Au thin layer could help to improve the crystal quality of the grown CBO films, promote the separation of photo-generated charges in the corresponding material and reduce the resistance of the system. In comparison with the FTO/CBO, the FTO/Au/CBO photocathode presents a remarkable improvement in the photocurrent, from −0.23 mA cm−2 to −0.50 mA cm−2 at 0.1 V vs. RHE. After optimizing the PEC system by depositing Pt nanoparticles on the CBO films, the plateau photocurrent was further amplified to −1.24 mA cm−2. These data indicate an attractive p-type material in photoelectrochemistry, without concern for the corrosion problem in aqueous electrolytes.

Fully understanding the positive roles of plasmonic nanoparticles in ameliorating the efficiency of organic solar cells

Herein, we constructed inverted PBDTTT-CF:PC70BM bulk-heterojunction organic solar cells by introducing Au nanoparticles to a ZnO buffer layer and a great improvement in energy conversion efficiency has been realized. To discover the positive roles of such plasmonic nanoparticles in the process of solar energy conversion, photovoltaic devices with the same architecture but different sized Au nanoparticles were purposely fabricated and it has been observed that the overall efficiency can be remarkably improved from 6.67% to 7.86% by embedding 41 nm Au nanoparticles in the buffer layer. The devices with other sizes of Au nanoparticles show a relatively low performance. Subsequent investigations including finite difference time domain simulation and transient photoluminescence studies reveal that the existence of the plasmonic particles could not only improve the optical absorption and facilitate the exciton separation, but can also benefit the collection of charge carriers. Thus, this paper provides a comprehensive perspective on the roles of plasmonic particles in organic solar cells and insights into the photo energy conversion process in the plasmonic surroundings.