电化学原位扫描显微红外反射光谱及其对铂表面CO吸附的红外成象

利用fOurIEr变换红外光谱仪 ,红外显微镜和X y扫描平台 ,通过设计和研制原位红外显微池和计算机接口及控制软件 ,建立了电化学原位扫描显微红外反射光谱 .研究工作显示 ,这一新的空间分辨原位红外反射光谱技术不仅可以获得固 /液界面环境中表面微区振动光谱的信息 ,还可以用于电极表面红外成象 .获得的CO在PT多晶电极表面吸附性能的化学图象在 10 -2 CM尺度上给出电极表面微区反应性能的不均一性及其分布 .国家杰出青年科学基金资助项目!(批准号:29525307

Electrochemical and in situ FTIR Spectroscopic Studies of CO2 Reduction on Polycrystalline Rh Surface

应用程序电位扫描法和电化学原位fTIr反射光谱从定量角度在分子水平上研究了CO2在rH电极上的电催化还原性能.红外光谱结果指出CO2还原的吸附产物为线型和桥式吸附态CO物种.在所研究的还原电位范围（-0.15~-0.40V）和相同还原时间，CO2还原吸附物种的氧化电量随还原电位的负移而增大，在每个还原电位下，时间超过250S时都可达到一个相应的饱和值.原位红外光谱和电化学研究结果均表明，CO2的还原与rH电极表面氢吸附反应密切相关，同时需要一定数量相邻表面位的参与.因此生成的CO不能在rH电极表面达到满单层吸附，而是形成均匀的亚单层分布The reduction of carbon dioxide on polycrystalline Rh electrode is studied by using programmed potential sweep method and in situ FTIR spectroscopy.Emphases are laid on the study of surface processes involved in the reduction.The adsorbed species derived from CO2 reduction (rCO2) have been determined by in situ FTIR as bridge(COB) and linear(COL) bonded CO, which yield IR absorption bands respectively around 1 905 and 2 020 cm-1.The onset potential of CO2 reduction has been determined at -0.05 V.The programmed potential sweep experiments demonstrated that the oxidation of rCO2 occurred in a current peak at about 036 V, from which the charge of rCO2 oxidation(Qox) has been measured quantitatively.It has been revealed that the Qox varies with the potential(Er) and the time(tr) applied for CO2 reduction.At a given tr, Qox increases along with the decrease of Er from -015 V to -040 V.At each Er, Qox reaches its saturation value (Qsox) when tr is longer than 250 s.In comparison with the oxidation charge(498 Ccm-2) for a saturation adsorption of CO on Rh electrode, the small value of Qsox(e.g., 270 Ccm-2 even for Er at -040 V) indicates that the quantity of adsorbed CO species produced in CO2 reduction is far from that of a monolayer coverage.The ratio of the intensity of IR band of bridge bonded CO to that of linear bonded CO is served to figure out the surface site occupancy by rCO2.In considering that the number of surface site occupied by bridge and linear bonded CO is 2 and 1 respectively, the surface site occupancy by rCO2 has been evaluated at only 73% for CO2 reduction at -025 V for 600 s.It has been demonstrated that the subsequent adsorption of CO on the 27% vacancy surface sites yields mainly linear bonded CO species, implying that the reduction of a CO2 molecule may need the assistance of a few adjacent surface sites.The in situ FTIR results also confirmed that the submonolayer of rCO2 is in a uniform distribution over Rh electrode surface.Finally, a reduction mechanism of CO2 on Rh electrode has been proposed based on results of both programmed potential sweep method and in situ FTIR spectroscopy, in which the hydrogen adsorption is considered as an important step assisting the reduction.国家自然科学基

Electrochemical and in situ FTIR spectroscopic studies of CO2 reduction on polycrystalline Rh surface

The reduction of carbon dioxide on polycrystalline Rh electrode is studied by using programmed potential sweep method and in situ FTIR spectroscopy. Emphases are laid on the study of surface processes involved in the reduction. The adsorbed species derived from CO2 reduction (r-CO2) have been determined by in situ FTIR as bridge(COB) and linear(COL) bonded CO2 which yield IR absorption bands respectively around 1905 and 2020 cm(-1). The onset potential of CO2 reduction has been determined at -0.05 V. The programmed potential sweep experiments demonstrated that the oxidation of r-CO2 occurred in a current peak at about 0.36 V, from which the charge of r-CO2 oxidation(Q(ox)) has been measured quantitatively. It has been revealed that the Q(ox) varies with the potential (E-r) and the time (t(r)) applied for CO2 reduction. At a given t(r), Q(ox) increases along with the decrease of E-r from -0.15 V to -0.40 V. At each E-r, Q(ox) reaches its saturation value (Q(ox)(s)) when t(r) is longer than 250 s. In comparison with the oxidation charge(498 mu C . cm(-2)) for a saturation adsorption of CO on Rh electrode, the small value of Q(ox)(s) (e. g., 270 mu C . Cm-2 even for E-r at -0.40 V) indicates that the quantity of adsorbed CO species produced in CO2 reduction is far from that of a monolayer coverage. The ratio of the intensity of IR band of bridge bonded CO to that of linear bonded CO is served to figure out the surface site occupancy by r-CO2. In considering that the number of surface site occupied by bridge and linear bonded CO is 2 and 1 respectively t the surface site occupancy by r-CO2 has been evaluated at only 73% for CO2 reduction at -0.25 V for 600 s. It has been demonstrated that the subsequent adsorption of CO on the 27% vacancy surface sites yields mainly linear bonded CO species, implying that the reduction of a CO2 molecule may need the assistance of a few adjacent surface sites. The in situ FTIR results also confirmed that the submonolayer of r-CO2 is in a uniform distribution over Rh electrode surface. Finally, a reduction mechanism of CO2 on Rh electrode has been proposed based on results of both programmed potential sweep method and in situ FTIR spectroscopy, in which the hydrogen adsorption is considered as an important step assisting the reduction

Studies of Electrocatalytic Properties of Electrode of Dispersed Pt on GC Support in Ethylene Glycol Oxidation

运用电化学循环伏安、阶跃电位、以及Ｘ－光衍射（ＸＲＤ）和扫描电镜（ＳＥＭ）等方法，研究了玻碳表面高分散铂电催化剂在不同条件下的结构与性能．结果指出，玻碳表面沉积的高分散铂黑经高温处理后具有一定的择优取向，晶粒尺寸变大，具有更好的稳定性和对乙二醇的电催化活性．The structures and properties of electrocatalyst of dispersed Plutinum(Pt) on glassy carbon(GC) support under different conditions were studied using cyclic voltammetry,potential step technique,x ray diffraction(XRD) and scanning Electron microscopy(SEM). The results indicated that after having been treated in high temperature,the dispersed Pt on GC support was recrystallised with preferented orientation,and the grain of Pt microcrystal become large and regular.It was illustrated that the dispersed Pt on GC support after high temperature treatment exhibited better stability and high activity for ethylene glycol oxidation.作者联系地址：厦门大学化学系固体表面物理化学国家重点实验室物化所,张掖师专化生系Author's Address: Dept. of chem., State Key Lab. for Phy. Chem. of the Solid Surf., Inst. of Phy. Chem., Xiamen Univ., Xiamen 361005 Xue Guoqing Dept. of Chem. and Biochem., teachers col

新重丰中子同位素~（239）Pa

用５０ＭｅＶ／ｕ１８Ｏ离子同天然铀靶反应产生了新重丰中子同位素２３９Ｐａ．用放射化学法从反应产物中分离Ｐａ活性，通过观测２３９Ｐａ及子体２３９Ｕ衰变所得到的结果显示：首次合成和鉴别了新重丰中子核素２３９Ｐａ，并测定出２３９Ｐａ的半衰期为１０６±３０ｍｉｎ．A new heavy neutron-rich isotope (239)Pa has been observed for the. first time in the interaction of 50MeV/u (18)O with (nat)U targets. Protactinium products were separated radiochemically from the complex mixture of the reaction products. The results observed from the decay of (239)Pa and its daughter (239)U show that a new heavy neutron-rich isotope (239)Pa was produced and identified. The measured half-life is 106±30 min.国家自然科学基金,中国科学院八·五重大项