Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Champaign, IL 61801, USA.
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.
Science. 2021 Feb 5;371(6529):626-632. doi: 10.1126/science.abc1339.
Solvent molecules influence the reactions of molecular hydrogen and oxygen on palladium nanoparticles. Organic solvents activate to form reactive surface intermediates that mediate oxygen reduction through pathways distinct from reactions in pure water. Kinetic measurements and ab initio quantum chemical calculations indicate that methanol and water cocatalyze oxygen reduction by facilitating proton-electron transfer reactions. Methanol generates hydroxymethyl intermediates on palladium surfaces that efficiently transfer protons and electrons to oxygen to form hydrogen peroxide and formaldehyde. Formaldehyde subsequently oxidizes hydrogen to regenerate hydroxymethyl. Water, on the other hand, heterolytically oxidizes hydrogen to produce hydronium ions and electrons that reduce oxygen. These findings suggest that reactions of solvent molecules at solid-liquid interfaces can generate redox mediators in situ and provide opportunities to substantially increase rates and selectivities for catalytic reactions.
溶剂分子影响氢气和氧气在钯纳米粒子上的反应。有机溶剂被激活形成反应性表面中间产物，通过与纯水反应不同的途径来介导氧气还原。动力学测量和从头算量子化学计算表明，甲醇和水通过促进质子-电子转移反应共同催化氧气还原。甲醇在钯表面生成羟甲基中间体，有效地将质子和电子转移给氧气，形成过氧化氢和甲醛。随后，甲醛将氢气氧化以再生羟甲基。另一方面，水异裂氧化氢气生成氢离子和电子，从而还原氧气。这些发现表明，固液界面处溶剂分子的反应可以原位生成氧化还原介质，并为提高催化反应的速率和选择性提供了机会。
