Yongfu Qiu

Nanowires of α- and β-Bi2O3: phase-selective synthesis and application in photocatalysis

This paper is focused on the first selective synthesis of α-and β-Bi2O3 nanowires by an oxidative metal vapour transport deposition technique. The nanowires growth conditions have been systematically investigated, providing insights into the mechanism of nanowires formation. We make a critical comparison of photocatalytic properties of the α- and β-Bi2O3 nanowires by the photo-degradation of Orange G under visible light. The β-Bi2O3 nanowires have shown the highest photo-catalytic activity under visible light of all the tested samples of Degussa TiO2 P25 and α-/β-Bi2O3 nanowires, which can be interpreted by the narrowest band gap of the β-Bi2O3 nanowires for the most effective harvest of the visible light as well as their smallest size for the most facile transfer of photo-excited electrons and the consequent most effective electron-hole separation.

Electrochemical route to the synthesis of ultrathin ZnO nanorod/nanobelt arrays on zinc substrate

An electrochemical route has been developed for the synthesis of highly ordered ZnO ultrathin nanorod and hierarchical nanobelt arrays on zinc substrate. A H2 gas sensor based on the ZnO nanobelt array exhibits excellent sensitivity, rapid response, and good reproducibility even at room temperature.

Surface functionalization of ZnO nanotetrapods with photoactive and electroactive organic monolayers.

Two strategies have been explored for organic functionalizations of ZnO nanotetrapods via anchoring groups of carboxylate and phosphonate. With these methods, oleyl chains were assembled on the surfaces of the ZnO nanotetrapods, significantly enhancing their solubility in nonpolar solvents, such as chloroform and toluene. The surface functionalization strategies have been extended to electroactive and photoactive molecules such as protoporphyrin and C(60) on the ZnO nanotetrapods. The surface-modified ZnO nanotetrapods were characterized comprehensively, revealing a uniform, covalently linked monolayer assembled on the surface. This work opens a broad perspective for the application of the organically functionalized nanotetrapods in optoelectronics and biomedicine.

Platinum(II) cyclometallates featuring broad emission bands and their applications in color-tunable OLEDs and high color-rendering WOLEDs

Two phosphorescent platinum(II) cyclometallated complexes with phenoxy groups (1 and 2) have been developed. The modified organic ligands derived by combining the phenoxy moiety and 2-phenylpyridine conferred them with a more flexible structure, leading to superior intermolecular interaction properties of the resulting Pt(II) metallophosphors. Because of the excimer formation induced by Pt(II) complexes 1 and 2, the emission color can be tuned over a wide range from cyan to orange by simply increasing the concentration of the Pt(II) metallophosphors. Inspired by their broad emission band, color tunability and outstanding electroluminescence (EL) performance, these two Pt(II) phosphors complemented with blue fluorescent emitter 4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl (BCzVBi) were employed in manufacturing high color-rendering white organic light-emitting devices (WOLEDs). In such simple two-emitter systems, 1-based WOLEDs exhibited reasonable EL performance with an external quantum efficiency (ηext) of 11.7%, luminance efficiency (ηL) of 29.1 cd A−1, power efficiency (ηp) of 16.9 lm W−1 and color rendering index (CRI) of 77, whereas 2-based WOLEDs demonstrated an ηext of 10%, ηL of 21.7 cd A−1, ηp of 10.7 lm W−1 and CRI of 88.

High performance electrochemical capacitors based on MnO2/activated-carbon-paper

In this research, the surface of commercial carbon paper was firstly activated with potassium dichromate lotion and then MnO2 nanoribbons were anchored onto the activated carbon paper (denoted as ACP) through an electrodeposition route. The as-prepared composite MnO2/ACP possessed a specific capacitance as high as 640.8 F g−1 calculated from the discharge curve with a current density of 10.0 A g−1 and this observation was deemed to originate from its enlarged specific surface area and improved electronic conductivity. Accordingly, the specific capacitances calculated from cyclic voltammograms were 617.0 and 395.0 F g−1 at a potential scan rate of 20 and 50 mV s−1, which kept 81.5% and 52.2% specific capacitance at 10 mV s−1 (757.0 F g−1). This indicated that the composite MnO2/ACP possessed good rate capability as an active electrode material for pseudo-capacitors. In a word, for the first time the composite MnO2/ACP has been reported as a promising electrode material for efficient supercapacitors.

Electrodeposition of manganese dioxide film on activated carbon paper and its application in supercapacitors with high rate capability

In this research magnesium dioxide (MnO2) is electrodeposited over activated carbon paper (ACP) to form a composited MnO2/ACP material. The as-prepared MnO2/ACP shows excellent capacitance performance with a high specific capacitance of 485.4 F g−1 calculated from a discharge curve with current density 2.0 A g−1, owing to its enlarged specific surface area and improved electronic conductivity. Moreover, the MnO2/ACP possesses remarkable rate capability due to the easy access of electrolytic ions, leading to complete utilization of MnO2 active material for supercapacitors. To summarize, the electrodeposition of MnO2 thin film on activated carbon paper is reported for the first time, and the composited MnO2/ACP is a promising electrode material for building up efficient supercapacitors.

Preparation of activated carbon paper through a simple method and application as a supercapacitor

As one of the most promising energy-storage devices, supercapacitors have drawn great research interests because of their outstanding electrochemical behavior. Carbon paper holds great prospect as an electrode material for supercapacitors since it is inexpensive and highly conductive. In this paper, the modified Hummer’s method is employed as an effective strategy to produce activated carbon paper with rougher surfaces and increased specific surface areas. It is further observed that hydrophilic groups such as hydroxyl (–OH), carbonyl (>C=O), and carboxyl (–COOH) have been introduced into the surface of carbon paper over treatment and they serve as strong polar sites to absorb water molecules, leading to improved hydrophilicity. Thus, the as-treated carbon papers with both increased specific surface areas and improved surface hydrophilicity exhibited excellent capacitive characteristics. Moreover, the charge/discharge test over 2000 cycles shows their excellent long-term capacitive retention.

Enhancing the photocatalytic H2 evolution activity of red phosphorous by using noble-metal-free Ni(OH)2 under photoexcitation up to 700 nm

Ni(OH)2 nanoparticles are demonstrated to be cost-efficient alternatives to Pt co-catalysts for enhancing the visible-light photocatalytic H2 evolution activity of red phosphorous (P) when deposited onto its surface. Ni(OH)2-modified red P exhibits 1.12 times higher photocatalytic activity for H2 evolution than that of Pt-deposited red P under a wide range of visible light.

Graphene-supported small tungsten carbide nanocrystals promoting a Pd catalyst towards formic acid oxidation

Using a microwave assisting method, we successfully synthesized tungsten carbide nanocrystals with a hexagonal prism shape on graphene (WCP/G). The WCP nanocrystals are 5 nm in size and dominated by (010), (100) and (100) facets with a preferred orientation of [0001]. An intermittent microwave heating (IMH) method is also utilized to load Pd nanoparticles (NPs) onto WCP/G to produce Pd–WCP/G, which displays a significant improvement as a catalyst for formic acid oxidation with peak current density increasing by a factor of 7, and notably enhanced durability. We believe this synthesis method of WCP/G opens new possibilities to research shape-controlled and high-surface-area transition metal carbide nanocrystals (TMCs) and developing them as efficient and low-cost catalysts or catalyst supports in a broad range of sustainable energy technologies.

Application of fault tree approach for the causation mechanism of urban haze in Beijing--Considering the risk events related with exhausts of coal combustion.

Haze weather has become a serious environmental pollution problem which occurs in many Chinese cities. One of the most critical factors for the formation of haze weather is the exhausts of coal combustion, thus it is meaningful to figure out the causation mechanism between urban haze and the exhausts of coal combustion. Based on above considerations, the fault tree analysis (FAT) approach was employed for the causation mechanism of urban haze in Beijing by considering the risk events related with the exhausts of coal combustion for the first time. Using this approach, firstly the fault tree of the urban haze causation system connecting with coal combustion exhausts was established; consequently the risk events were discussed and identified; then, the minimal cut sets were successfully determined using Boolean algebra; finally, the structure, probability and critical importance degree analysis of the risk events were completed for the qualitative and quantitative assessment. The study results proved that the FTA was an effective and simple tool for the causation mechanism analysis and risk management of urban haze in China.