Shao M H, Adzic R R
Department of Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA.
J Phys Chem B. 2005 Sep 8;109(35):16563-6. doi: 10.1021/jp053450s.
Surface enhanced infrared reflection-absorption spectroscopy with an attentuated total reflection configuration (ATR-SEIRAS) was used for the first time to identify the intermediates of the oxygen reduction reaction (ORR) on gold electrodes. Our study employed a Au thin-film electrode in acidic and alkaline solutions. In alkaline solutions, a potential dependent band at 1268 cm(-1), which we assigned to the antisymmetric bending mode of OOH of adsorbed HO2-, was observed between 0.1 and -0.6 V versus Ag|AgCl, Cl-, exactly in the potential range where the ORR occurred. The assignment was supported by our isotope exchange experiment. The adsorbed HO2- is a reaction intermediate in the 4e- serial mechanism. In acidic solutions, there was only a very weak band at the same position, reflecting the fast protonation of HO2-. This finding may imply that the interaction between HO2- and Au surfaces is very weak in acidic solutions, in agreement with the observed 2e- reduction mechanism.
首次使用具有衰减全反射配置的表面增强红外反射吸收光谱(ATR - SEIRAS)来识别金电极上氧还原反应(ORR)的中间体。我们的研究在酸性和碱性溶液中使用了金薄膜电极。在碱性溶液中,相对于Ag|AgCl,Cl -,在0.1至 - 0.6 V之间观察到一个位于1268 cm(-1) 的与电位相关的谱带,我们将其归属于吸附的HO2- 的OOH的反对称弯曲模式,该电位范围恰好是ORR发生的电位范围。我们的同位素交换实验支持了这一归属。吸附的HO2- 是4e - 串联机制中的反应中间体。在酸性溶液中,在相同位置只有一个非常弱的谱带,这反映了HO2- 的快速质子化。这一发现可能意味着在酸性溶液中HO2- 与金表面之间的相互作用非常弱,这与观察到的2e - 还原机制一致。