甘氨酸修饰的Pt(111)电极上的氧还原

利用单晶旋转圆盘电极技术（Hanging Meniscus Rotating Disk Electrode,　HMRD）在硫酸和高氯酸溶液中分别研究了甘氨酸修饰的Pt(111)电极表面氧分子的电催化还原反应. 实验发现：在硫酸溶液中，经甘氨酸修饰的Pt(111)电极表面的氧还原活性明显提高，其中氧还原的半波电位与Pt(111)电极的相比正移约0.1 V，而在高氯酸溶液中，甘氨酸修饰的Pt(111)电极的活性几乎没有发生变化. 该实验结果表明：甘氨酸修饰的Pt(111)电极一方面抑制了SO₄^2-在电极表面的吸附，另一方面又能在电极表面提供相邻的空位供氧分子吸附. 通过与文献中报道的CN^-修饰的Pt(111)电极上的氧还原结果的对比，可以推测甘氨酸修饰的Pt(111)电极表面氧还原活性提高是由于甘氨酸在Pt(111)表面可能先被氧化成CN^-后吸附在电极表面，进而促进了氧分子的电催化还原反应.

Oxygen Reduction Reaction on Glycin Modified Pt(111) Electrode

Oxygen reduction reaction (ORR) on glycin (NH2CH2COOH) modified Pt(111) electrode has been investigated using hanging meniscus rotating disk electrode system (HMRD) in 0.05 mol•L^-1 H₂SO₄ and 0.1 mol•L^-1 HClO₄ solutions, respectively. Cyclic voltammograms of the glycin modified Pt (111) electrode measured in 0.05 mol•L^-1 H₂SO₄ solution similar to that of CN^- modified Pt(111) electrodes, demonstrating that sulfate adsorption is strongly inhibited at the glycin modified Pt(111). From the polarization curve of ORR recorded in 0.05 mol•L^-1 H₂SO₄ solution, it is found that the ORR activity at the glycin modified Pt (111) is greatly enhanced with the half wave potential (E_1/2) of ORR being shifted ca. 0.1 V positively, which is close to the activity of ORR at the unmodified Pt(111) in 0.1 mol•L^-1 HClO₄ solution. The improved ORR activity is explained by geometric effect due to the formation of well organized CN^- adlayer at Pt(111) from the oxidative decomposition of glycin, which effectively inhibits the adsorption of sulfate anions.