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用循环伏安法研究了多晶金电极在0.1 mol/L HClO4和0.1 mol/L KOH中氢析出反应的温度效应.在278~333 K时,随温度和电位的增加氢析出反应电流显著增加, 在酸性溶液中Tafel斜率从118 mV/dec增加到146 mV/dec,超电势从0.2 V增加到0.35 V时,其活化能从37 kJ/mol降低至30 kJ/mol,反应的指前因子比在碱性溶液中的高出一个数量级.在碱性溶液中Tafel斜率约为153±15 mV/dec,且未呈现明显随温度变化的趋势.平衡电位的反应活化能在酸性和碱性溶液中分别约为48和34 kJ/mol.当超电势增加时,在碱性溶液中的指前因子单调增加,在酸性溶液中指前因子不随电位而变化.还讨论了金电极上氢析出反应在酸性和碱性溶液中具有不同的随电势变化的动力学参数的原因及其与反应机理的联系. 相似文献
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本文利用循环伏安法和电化学原位红外光谱的联用,研究了Pt(111)和Pt膜电极在CO2饱和的酸性溶液中氢析出和CO2还原的竞争. 发现:(i)在pH>2的溶液中,主要反应是氢析出,界面pH值随着氢析出突然增加;(ii)通过红外光谱检测,COad是CO2还原过程中唯一的吸附中间体;(iii)COad生成速率随着欠电位沉积氢(UPD-H)覆盖的增加而增大,并在氢析出的起始电位达到最大值;(iv)在氢析出时,COad的减少与CO2吸附和还原所必需的的中间产物(Had)有限的可用位点和停留时间相关. 相似文献
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本文使用循环伏安法和电势阶跃法分别研究了添加和不添加Na2SO4的0.1 mol/LH2SO4+0.1 mol/LHCOOH溶液中Pd(111)电极上甲酸氧化反应(FAO)的动力学行为,并与同样条件下0.1 mol/LHClO4中的动力学行为进行比较. 加入0.05 mol/L或者0.1 mol/LNa2O4后,在相同的电位下负向扫描的FAO电流比正向扫描的显著减小. 本文推测在(SO4*ad)m+[(H2O)n-H3O+]或(SO4*ad)m+[Na+(H2O)n-H3O+]吸附层相转变电势以正的电位, 这个吸附层的结构可能随着电位的增加或Na2SO4的加入变得更加致密和稳定. 因此,破坏或者脱附致密的硫酸(氢)根吸附层变得更加困难,使得FAO 动力学在较高电位和随后的负扫电位受到明显的抑制. 相似文献
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The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) occurring at the Raney-Ni mesh electrode in 30 wt.-% aqueous KOH solution were studied in the absence (silent) and presence of ultrasound (408 kHz, ∼54 W, 100% acoustic amplitude) at different electrolyte temperatures (T = 25, 40 and 60 °C). Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) experiments were performed to analyse the electrochemical behaviour of the Raney-Ni electrode under these conditions. Under silent conditions, it was found that the electrocatalytic activity of Raney-Ni towards the HER and the OER depends upon the electrolyte temperature, and higher current densities at lower overpotentials were achieved at elevated temperatures. It was also observed that the HER activity of Raney-Ni under ultrasonic conditions increased at low temperatures (e.g., 25 °C) while the ultrasonic effect on the OER was found to be insignificant. In addition, it was observed that the ultrasonic effect on both the HER and OER decreases by elevating the temperature. In our conditions, it is suggested that ultrasound enhances the electrocatalytic performance of Raney-Ni towards the HER due to principally the efficient gas bubble removal from the electrode surface and the dispersion of gas bubbles into the electrolyte, and this effect depends upon the behaviour of the hydrogen and oxygen gas bubbles in alkaline media. 相似文献