The direct formic acid fuel cell holds great promise as a next generation portable power source. Here we report an experimental study on Pt and Pd monolayer (Pt* and Pd*) atop the close-packed facet of transition metal substrates (denoted Pt*/M or Pd*/M, where M = Pt, Pd, Ir, Au, Rh and Ru) model catalysts for formic acid oxidation (FAO) and demonstrate a promotional effect on Pt*/Au(111) and Pd*/Pt(111) surfaces. Contrary to findings on monometallic surfaces, in situ infrared reflection adsorption spectroscopy collected during formic acid oxidation at potentials anodic of 375 mV reveal that the poisoning reaction intermediate CO is not formed on the monolayer surfaces, suggesting a promotion of the direct mechanisms of FAO at the expense of the indirect mechanism through CO. Our density functional theory calculations on model surfaces with 1:1 stoichiometry for overlayer to support metal atoms for the thermochemistry of the elementary steps defined by adsorbed CO, OH, COOH, and HCOO on the (111) facet of Pt, Pt_ML/Au, Pd, and Pd_ML/Pt largely attribute the promotional effect observed for the monolayer catalysts to easier removal of CO brought about by easier activation of water, relative to the monometallic catalysts. This synergy between experiments and theory brings us closer to a fundamental understanding of FAO electrocatalysts under reaction conditions, paving the way to achieving more active electrocatalysts possibly with less Pt or Pd; a pre-requisite for the mass commercialization of this technology.

直接甲酸燃料电池作为下一代便携式电源具有广阔的前景。在这里，我们报告了在过渡金属基材（表示为Pt * / M或Pd * / M，其中M = Pt，Pd，Ir，Au的密排小面）上的Pt和Pd单层（Pt *和Pd *）的实验研究，Rh和Ru）用于甲酸氧化（FAO）的模型催化剂，并证明对Pt * / Au（111）和Pd * / Pt（111）表面具有促进作用。与单金属表面上的发现相反，在甲酸氧化过程中以375 mV的阳极电位采集的原位红外反射吸附光谱表明，在单层表面上未形成中毒反应中间体CO，这提示了粮农组织在该层上的直接机制得到了促进。通过CO间接机制的费用。我们在模型表面上的密度泛函理论计算为：相对于单金属催化剂，_ML / Au，Pd和Pd _ML / Pt在很大程度上将观察到的对单层催化剂的促进作用归因于由较容易的水活化引起的更容易除去的CO。实验与理论之间的这种协同作用使我们更加了解反应条件下对粮农组织电催化剂的基本了解，从而为可能以更少的Pt或Pd获得更多活性的电催化剂铺平了道路。该技术大规模商业化的前提条件。