Optimal Electrocatalytic Pd/MWNTs Nanocatalysts toward Formic Acid Oxidation

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• 作者：Yiran Wang^a ; Qingliang He^a ; Huige Wei^b ; Jiang Guo^a ; Keqiang Ding^c ; Qiang Wang^d ; Zhe Wang^e ; Suying Wei^b ; ^{suying.wei@lamar.edu" class="auth_mail" title="E-mail the corresponding author} ; Zhanhu Guo^a ; ^{zguo10@utk.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：formic acid oxidation ; dual pathway ; palladium based catalysts ; concentration effect ; temperature effect
• 刊名：Electrochimica Acta
• 出版年：2015
• 出版时间：1 December 2015
• 年：2015
• 卷：184
• 期：Complete
• 页码：452-465
• 全文大小：2229 K

文摘

The operating conditions such as composition of electrolyte and temperature can greatly influence the formic acid (HCOOH) oxidation reaction (FAOR). Palladium decorated multi-walled carbon nanotubes (Pd/MWNTs) were successfully synthesized and employed as nanocatalysts to explore the effects of formic acid, sulfuric acid (H₂SO₄) concentration and temperature on FAOR. Both the hydrogen adsorption in low potential range and the oxidation of poisoning species during the high potential range in cyclic voltammetry were demonstrated to contribute to the enhanced electroactivity of Pd/MWNTs. The as-synthesized Pd/MWNTs gave the best performance under a condition with balanced adsorptions of HCOOH and H₂SO₄ molecules. The dominant dehydrogenation pathway on Pd/MWNTs can be largely depressed by the increased dehydration pathway, leading to an increased charge transfer resistance (R_ct). Increasing HCOOH concentration could directly increase the dehydration process proportion and cause the production of CO_ads species. H₂SO₄ as donor of H⁺ greatly facilitated the onset oxidation of HCOOH in the beginning process but it largely depressed the HCOOH oxidation with excess amount of H⁺. Enhanced ion mobility with increasing the temperature was mainly responsible for the increased current densities, improved tolerance stabilities and reduced R_ct values, while dehydration process was also increased simultaneously.