Sun Shigang

Kinetics of dissociative adsorption of formic acid on Pt(100), Pt(610), Pt(210) and Pt(110) single-crystal electrodes in perchloric acid solutions

Abstract The kinetics of dissociative adsorption of HCOOH on Pt(100), Pt(610), Pt(210) and Pt(110) single-crystal electrodes has been investigated. The oxidation of dissociative adsorbate (DA) derived from the dissociative adsorption of HCOOH was used as a probe reaction together with the potential-step technique of short time windows. The quantity Q ad of DA produced at a given potential E ad and in a defined time window t ad of adsorption has been determined systematically. At fixed t ad peaked curves of Q ad versus E ad in the potential range between −0.25 and 0.25 V/SCE have been obtained on all four electrodes. The maximum rate of dissociative adsorption of HCOOH decreases in the order Pt(110) ⪢ Pt(210) ⪢ Pt(610) ⪢ Pt(100).

INVESTIGATIONS OF COADSORPTION OF CARBON-MONOXIDE WITH S OR BI ADATOMS AT A PLATINUM-ELECTRODE BY IN-SITU FTIR SPECTROSCOPY AND QUANTUM-CHEMISTRY ANALYSIS

Abstract The adsorption of CO on a Pt electrode was used as a molecular probe, and the surface properties with respect to the electronic structure of the Pt electrocatalyst during modification by S or Bi adatoms were investigated by a combination of cyclic voltammetry, in-situ Fourier transform IR (FTIR) spectroscopy and cluster model analysis using self-consistent charge discrete variational X α (SCC-DV-X α ) calculations. It is found that the S adatom decreases the ability of the Pt surface to donate electrons, resulting in weakened CO adsorption and increasing vibrational frequency of the CO band of adsorbed CO molecules. However, the opposite effects were observed in the case of Bi adatoms. The electronic and vibrational properties of the potential dependence of CO adsorbed on a Pt electrode were also studied carefully. The results of quantum chemistry calculations are in good agreement with the experimental results of in-situ FTIR spectroscopy and also reveal the deeper significance of the IR spectroscopy data.

In situ FTIRS features during oxygen adsorption and carbon monoxide oxidation at a platinum electrode in dilute alkaline solutions

Abstract Oxygen adsorption and CO oxidation at a Pt electrode in dilute alkaline solutions were studied using the single-potential alteration Fourier transform IR spectroscopy (SPAFTIRS) technique. The results demonstrated that the concentration of OH − in solution plays an important role in the oxidation of CO ad and the retention of the CO 2 product of this oxidation. The band due to the CO 2 asymmetrical stretch will appear in spectra only when OH − species near the Pt surface in the thin layer between the electrode and the IR window have reached a very low concentration. The experimental data reported here show that CO ad may be attacked by OH − species in solution even in the potential region of hydrogen adsorption. In a concentrated base solution the negative-going peak of the CO ad bipolar band corresponding to IR absorption by CO ad at the sample potential disappears rapidly from the spectra with increasing sample potential, and no CO 2 band is observed. During oxygen adsorption and CO oxidation the FTIR spectra are dominated by a curved region between 3000 and 1700 cm −1 and a progressive increase in the intensity of a band near 1650 cm −1 , which is defined as “OH − loss structure” and is due to the concentration variation of components, i.e. the loss of OH − and the production of H 2 O species in the thin layer.

Study of pyrolyzed hemin/C as non-platinum cathodic catalyst for direct methanol fuel cells

Biological reduction of O2 to H2O justifies a serious look at heme as a potential O2 reduction reaction (ORR) catalyst for low temperature fuel cells. In this study, a novel non-platinum electrocatalyst for ORR was prepared through hemin, which is hydrochloride of heme, supported on Black Pearls 2000 carbon black (Hm-BP) pyrolyzed at 700–900 °C in Ar atmosphere. The physical and electrocatalytic properties of as-prepared catalysts were characterized by TGA, XRD, XPS, TEM, rotating disk electrode (RDE) and rotating ring disk electrode (RRDE). It has found that the catalyst treated at 750 °C (Hm-BP-750) exhibits the best property among the Hm-BP catalysts prepared. The onset potential of ORR on the Hm-BP-750 at 30 °C was measured ca. 0.90 V (vs. RHE) in 0.1 M H2SO4, and mass current density was reached 15.3 mA mg−1 at 0.75 V. It has revealed that O2 could be reduced directly to water in a 4e process between 0.9 and 0.83V, and the yield of H2O2 was 0–18% in the potential range of 0.83–0.63 V. This methanol-tolerant catalyst also presents excellent stability in medium-term test of direct methanol fuel cell at 80 °C.

Room Temperature Synthesis of Thorn-Like Pd Nanoparticles and Their Enhanced Electrocatalytic Property for Ethanol Oxidation

National Natural Science Foundation of China [20833005, 20873116, 60936003]; Supramolecular Structure and Materials, State Key Laboratory, China [SKLSSM200910]

Electrochemically shape-controlled formation of concave AuPd alloy nanoparticles on ITO substrate

Shape-control of AuPd alloy nanoparticles (AuPd NPs) substrated on indium-tin oxide (ITO) was successfully achieved, for the first time, by using electrochemical square-wave-potential (SWP) method. Concave trisoctahedral AuPd alloy NPs (TOH AuPd NPs) and concave hexoctahedral AuPd alloy NPs (HOH AuPd NPs) were prepared under SWP conditions with lower potential of 0.3 V while different upper potentials of 0.64 and 0.70 V, respectively. Different techniques including SEM, EDX and electrochemical cyclic voltammetry were employed to characterize the morphology and composition of AuPd alloy NPs. The results demonstrated that the as-prepared TOH AuPd NPs and HOH AuPd NPs are uniform in shape of correspondingly concave TOH and concave HOH, and are well dispersed on the ITO substrate. The composition in terms of and Au:Pd atomic ratio of both TOH and HOH AuPd alloy NPs is determined by EDX around 3:1. However, a surface enrichment of Au on the AuPd NPs was observed, and is ascribed to the lower surface energy of Au in comparison with that of Pd. It has been found that, starting from the as-synthesized TOH AuPd NPs, shape transformation from TOH to HOH can be accomplished by applying a treatment of square wave with lower potential of 0.3 V and upper potential of 0.7 V. Prolonging the treatment time results in increasing the size of AuPd NPs, while the HOH shape is preserved.

不同碳源合成Na 2 MnPO 4 F/C及其作为锂离子电池正极材料的性能

National Natural Science Foundation of China [50574063, 21021002, 21003102]; Sichuan University Funds for Young Scientists, China [2011SCU11081]; Research Fund for the Doctoral Program of Higher Education, the Ministry of Education, China [20120181120103]

铁、氮掺杂石墨烯/碳黑复合材料的制备及氧还原电催化性能

以高含氮量的2-氨基咪唑为氮源,三氯化铁为铁源,高比表面积的KJ600碳黑为载体,通过水热法制得氨基咪唑聚合物前驱体,再经二次高温热处理,制得石墨烯/碳黑复合材料.透射电镜表征显示该材料为石墨烯纳米片与碳黑颗粒的复合结构.BET表征表明这是一种多孔结构,具有很高的比表面积（882 m~2·g~（-1））,这有利于暴露更多活性位点,并促进传质.XRD证实催化剂中存在石墨烯,且石墨烯结构是在第一次热处理过程中形成的.电化学测试表明,该催化剂在酸性和碱性介质中都具有很高的氧还原电催化活性和低H_2O_2产率,并且在碱性介质中对甲醇小分子的抗毒化性能明显优于商业Pt/C催化剂,展示出在实际燃料电池系统中的应用潜力.

Effects of Surface Properties and Microstructures of Carbon Nanofibers on Their Electrocatalytic Activity for Oxygen Reduction Reaction

Two types of carbon nanofibers(CNFs),tubular CNFs(t-CNFs) and fish-bone CNFs(f-CNFs) were synthesized and the effects of surface properties of CNFs on their electrocatalytic activity for oxygen reduction reaction(ORR) in alkaline media were investigated.Oxygen- and nitrogen-containing functional groups were introduced onto the CNF surface by sonochemical oxidation in mixed acids(concentrated sulfuric acid and nitric acid) and ammonia,respectively.The ORR activities of the CNF catalyst were measured in an oxygen-saturated 0.1 mol/L KOH electrolyte solution by rotating disk electrode(RDE) technique.The RDE results show that the electrocatalytic activities of the two types of CNFs increase in the same sequence untreated CNFs oxygen-containing CNFs nitrogen-containing CNFs,while the f-CNFs-based catalysts have higher electrocatalytic activities for ORR than t-CNFs-based counterparts.The results indicate that both the surface properties and the microstructures of CNFs have effects on the electrocatalytic activity of CNFs for ORR,although the former may have a dominant effect.

Preparation of Dendritic Pt Thin Films and Their Anomalous Infrared Effects

National Natural Science Foundation of China [21073152, 20933004, 20833005, 21021002]; Outstanding Young Scientific Talents Cultivation Plan of Colleges in Fujian Province, China [JA10003]