De-Sheng Kong

Synergistic degradation of rhodamine B on BiOClxBr1−x sheets by combined photosensitization and photocatalysis under visible light irradiation

BiOClxBr1−x sheets were synthesized by a simple precipitation method. These samples showed good activities in the degradation of rhodamine B (RhB) under visible light irradiation (420 nm < λ < 800 nm). From a series of characterization techniques, the results showed that the degradation was driven by the photosensitization of RhB and photocatalysis of BiOClxBr1−x. The mechanism of the synergistic degradation processes was explored by comparing the degradation properties of BiOClxBr1−x (Cl : Br = 1 : 1) and BiOBr. The main active species that played important roles in the degradation process were electrons and O2˙− in the BiOClxBr1−x (Cl : Br = 1 : 1) system, while in the BiOBr system, electrons, O2˙− and holes were the main active species. Such a heterogeneous synergistic degradation reaction has much significance in revealing the degradation mechanism of organic pollutants in ordinary photocatalysis.

An Electrochemical Study on the Anodic Oxygen Evolution on Oxide Film Covered Titanium

Anodic oxygen evolution reaction on titanium oxide film and its affect on the surface and bulk properties of the film is an important subject in the Ti-based studies and applications. In this work, the behavior of oxygen evolution and some other related electrode processes occurring at anodically grown TiO 2 films on titanium were investigated within a relatively wide potential range by electrochemical measurements in 1 M perchloric acid solution. For the formation of the oxide film, three potential regions (two passive regions and the film breakdown region) were selected. The changes both in surface properties (mainly caused by oxygen evolution) and in bulk properties (mainly caused by increased potential) were taken into account for the observed different oxygen evolution behavior. The origin of a cathodic current peak at -0.2 V revealed in cyclic voltammograms was attributed to the reduction of the oxygen atoms adsorbed/absorbed at the oxide film surface, which were generated during anodic oxygen evolution. The flatband potential for the anodically formed titanium oxide films in 1.0 M HClO 4 was estimated as -0.2 V. With the semiconducting energy band structure models constructed for the Ti/oxide film/1 M HClO 4 electrode system, both the different behavior for anodic oxygen evolution on the titanium oxide films formed at different potentials and the electron transfer processes for the electrochemical reactions observed in this work were further interpreted.

Relationship between surface hydroxyl groups and liquid-phase photocatalytic activity of titanium dioxide.

Both theories and experiments show that surface hydroxyl radicals (OH) are the most important intermediate species in the photocatalytic process. As a source of OH, surface hydroxyl (OH) groups play an important role in its generation. In this paper, the OH groups were divided into surface acidic hydroxyl (OH(a)) and surface basic hydroxyl (OH(b)) groups. From the detection by a method of surface acid-base, ion-exchange reactions, the total surface density of OH groups was about 9.58×10(-5) mol m(-2). The results measured by Fourier transform infrared spectroscopy, (1)H magnetic-angle spinning NMR and electron spin resonance techniques demonstrated that the role of OH(a) groups was greater than that of OH(b) groups on the generation of OH radicals. By degradation of methyl orange, rhodamine B and p-chlorophenol, the photocatalytic activities of the catalysts were directly influenced by the amount of OH groups.

Electrochemical Anodic Dissolution Kinetics of Titanium in Fluoride-Containing Perchloric Acid Solutions at Open-Circuit Potentials

The influence of fluoride on the anodic dissolution kinetics of titanium was studied by several electrochemical techniques at steady-state open-circuit potentials in 1.0 M HClO 4 containing fluoride with various concentrations ranging from 0 to 0.1 M. The promoting effect of fluoride (especially when [F - ] > 1 × 10 -3 M) on the anodic dissolution behavior of titanium was characterized and discussed by taking into account the changes in the estimated electrochemical and kinetic parameters. The faradaic impedance for the anodic dissolution of titanium was analyzed both by fitting based on an equivalent electrical circuit model and by theoretical derivation based on a two-step mechanism involving one adsorbed intermediate species. By correlating the faradaic impedance expression derived from the dissolution mechanism with that deduced from the equivalent electrical circuit model, some important kinetic parameters (such as the apparent rate constants K 1 and K 2 and the surface coverage θ ss ) could be estimated from the equivalent circuit elemental parameters (such as R c1 , R a , and C a ). The charge-transfer reaction was the rate-determining step at lower fluoride concentrations of [F - ] ≤ 1 × 10 -3 M, leading to a high surface coverage of θ ss = 1, while the chemical dissolution reaction is the rate-determining step at higher fluoride concentrations of [F-] > 1 × 10 -3 M, leading to a decreased surface coverage of θ ss < 0.5.

Promoting effect of polyaniline on Pd catalysts for the formic acid electrooxidation reaction

Abstract Pd-based nanomaterials have been considered as an effective catalyst for formic acid electrooxidation reaction (FAOR). Herein, we reported two types of polyaniline (PANI)-promoted Pd catalysts. One was an n PANI/Pd electrocatalyst prepared by the electropolymerization of aniline and the electrodeposition of Pd. The other was a Pd/C/ n PANI catalyst prepared by the direct electropolymerization of aniline on a commercial Pd/C catalyst. The results show that PANI alone has no catalytic activity for FAOR; however, PANI can exhibit a significant promoting effect to Pd. The current densities of FAOR on the Pd catalysts with a PANI coating show a significant increase compared with that of the Pd reference catalyst without PANI as a promoter. The promoting effects of PANI are strongly dependent on the electropolymerization potential cycles ( n ). The highest catalytic activities for FAOR of all the n PANI/Pd and Pd/C/ n PANI catalysts were those of 15PANI/Pd and Pd/C/20PANI. The mass-specific activity (MSA) of Pd in 15PANI/Pd was 7.5 times that of the Pd catalyst, and the MSA and intrinsic activity of Pd/C/20PANI were 2.3 and 3.3 times that of the Pd/C catalyst, respectively. The enhanced performance of Pd catalysts is proposed as an electronic effect between Pd nanoparticles and PANI.

Dealloyed PdAg core Pt monolayer shell electrocatalyst for oxygen reduction reaction

A core–shell nanostructure (Pt–PdAg/C–D) with dealloyed PdAg nanoparticles (PdAg/C–D) as the core and a Pt monolayer as the shell is prepared and employed as an electrocatalyst toward oxygen reduction reaction (ORR). Compared with its counterpart alloyed PdAg core-Pt monolayer shell catalyst (Pt–PdAg/C), the Pt–PdAg/C–D catalyst shows significantly higher catalytic activities for ORR. The half wave potential (E1/2) on Pt–PdAg/C–D is located at −0.17 V, which is comparable to that on the commercial Pt/C catalyst and ca. 30 mV more positive than that on Pt–PdAg/C. The MSA of Pt in Pt–PdAg/C–D is 171.8 A gPd+Pt−1, which is 3.2 and 2.4 times higher than those of Pt–PdAg/C and commercial Pt/C catalysts, respectively. The Pt monolayer shell on the surface of the nanoparticles would induce much higher utilization of Pt atoms, and the dealloying process would result in a nanostructured PdAg core with a rough surface and a Pt shell with a numbers of low-coordinated atoms. It is concluded that the change in the electronic and geometric structure of Pt in the Pt–PdAg/C–D catalyst may contribute to the increase in catalytic performance for ORR.

Electrochemical Fabrication and Pseudocapacitive Performance of a Porous Nanostructured Nickel-Based Complex Film Electrode

[Kong De-Shuai; Wang Jian-Ming; Pi Ou-Yang; Shao Hai-Bo; Zhang Jian-Qing] Zhejiang Univ, Dept Chem, Hangzhou 310027, Peoples R China. [Zhang Jian-Qing] Chinese Acad Sci, Inst Met Res, State Key Lab Corros & Protect Met, Shenyang 110016, Peoples R China.;Wang, JM (reprint author), Zhejiang Univ, Dept Chem, Hangzhou 310027, Peoples R China;wjm@zju.edu.cn