Perry S C, Denuault G
Chemistry, University of Southampton, Southampton, SO17 1BJ, UK.
Phys Chem Chem Phys. 2016 Apr 21;18(15):10218-23. doi: 10.1039/c6cp00106h. Epub 2016 Mar 29.
Using chronoamperometry and voltammetry at oxide-free microelectrodes in non-adsorbing electrolyte, KClO4, we investigated the reduction of oxygen containing species which adsorb at potentials below those where oxides are grown electrochemically when the electrode is exposed to dissolved oxygen. Their coverage is found to vary with the metal substrate as follows, Ni > Cu > Pt > Ag, and is negligible on Au microdiscs. This dependence is consistent with the adsorption energy of atomic oxygen for the respective metals predicted by DFT. Furthermore the adsorption energies derived from the stripping peak potentials for the different metals agree very well with those predicted by the DFT calculations. We exploit the oxygen coverage differences between Pt, Pt0.9Rh0.1 and Pt0.9Ir0.1 microdiscs to predict the adsorption energy of these species on the Pt alloys and demonstrate a clear correlation between the metal activity towards the ORR and the charge associated with the reduction of the adsorbed oxygen species. In effect the coverage - adsorption energy relationship turns the charge associated with the reduction of the adsorbed oxygen species into a descriptor of the electrode activity towards the ORR. This study provides new insight into the oxygen reduction reaction and offers a new methodology to investigate low temperature fuel cell ORR catalysts.
在非吸附性电解质高氯酸钾（KClO₄）中，使用无氧化物微电极上的计时电流法和伏安法，我们研究了含氧化合物的还原过程。当电极暴露于溶解氧时，这些含氧化合物在低于电化学生长氧化物的电位下吸附。发现它们的覆盖度随金属基底变化如下：Ni > Cu > Pt > Ag，在金微盘上可忽略不计。这种依赖性与密度泛函理论（DFT）预测的各金属对原子氧的吸附能一致。此外，从不同金属的溶出峰电位得出的吸附能与DFT计算预测的结果非常吻合。我们利用铂（Pt）、铂铑（Pt₀.₉Rh₀.₁）和铂铱（Pt₀.₉Ir₀.₁）微盘之间的氧覆盖度差异来预测这些物种在铂合金上的吸附能，并证明了金属对氧还原反应（ORR）的活性与吸附的氧物种还原相关电荷之间存在明显的相关性。实际上，覆盖度 - 吸附能关系将与吸附的氧物种还原相关的电荷转化为电极对ORR活性的描述符。这项研究为氧还原反应提供了新的见解，并提供了一种研究低温燃料电池ORR催化剂的新方法。
