NH_4^+对甲酸在炭载Pd催化剂上氧化性能的影响

Effect of NH_4^+ on the Electrocatalytic Performance of Carbon Supported Pd Catalyst for Formic Acid Oxidation

为了解HClO4、NH4ClO4和NaClO4电解液对炭载Pd(Pd/C)催化剂电极对甲酸氧化的电催化性能的影响,在用X射线衍射(XRD)谱、能量色散谱(EDS)和透射电子显微镜(TEM)对Pd/C催化剂进行表征的基础上,采用电化学方法测量了Pd/C催化剂在不同电解液中对甲酸氧化的电催化性能.发现在不同电解液中,Pd/C催化剂对甲酸氧化的电催化活性和稳定性按NH4ClO4>NaClO4>HClO4的次序降低.由于甲酸的存在,不同电解液的pH相差较小,因此,电解液的pH影响较小,而阳离子的影响较大.在NaClO4电解液中的性能优于在HClO4电解液中的性能是pH的影响.在NH4ClO4电解液中的性能优于在NaClO4电解液中是由于NH4+能降低CO在Pd/C催化剂电极上的吸附强度和吸附量,这一发现对提高直接甲酸燃料电池(DFAFC)的性能很有意义.

We investigated the effect of HClO4, NH4ClO4, and NaClO4 electrolytes on the electrocatalytic performance of a Pd/C catalyst electrode for formic acid oxidation. The Pd/C catalyst was characterized by X-ray diffraction （XRD）, energy dispersive spectroscopy （EDS）, and transmission electron microscopy （TEM）. The performance of the Pd/C catalyst electrode during formic acid oxidation in different electrolytes was measured using electrochemical methods. We found that the electrocatalytic activity and stability of the Pd/C catalyst electrode for formic acid oxidation decreased in the following order： NH4ClO4〉 NaClO4〉 HClO4. The difference in pH between the different electrolytes was small because of the presence of formic acid. Therefore, the electrolyte pH has a small effect and the cations have a large effect. The better performance of the NaClO4 electrolyte compared to the HClO4 electrolyte is due to a pH effect. The better performance of the NH4ClO4 electrolyte compared to the NaClO4 electrolyte is due to NH4＋ decreasing the adsorption strength and amount of CO on the Pd/C catalyst. This finding has large significance for the increase in the performance of the direct formic acid fuel cell （DFAFC）.