Surface properties of ferroelectrics are promising for catalysis due to the spontaneous electric polarization that can be reversed by an applied electric field. While several theoretical studies show different catalytic activities for differently polarized ferroelectric surfaces at zero electric potential, little work was devoted to catalysis on ferroelectric surfaces at higher electric potentials. Under these conditions that are relevant for photocatalytic experiments and applications, surfaces are usually oxidized. Using density functional theory calculations, we show for LaTiO2N and BaTiO3 that this oxidation heavily impacts and even determines the electronic properties of the catalyst surface and therefore leads to similar reaction free energies for the catalytic steps of the oxygen evolution reaction, irrespective of the bulk polarization. This is opposed to experimental studies, which found different activities for differently polarized catalyst surface domains under oxidizing conditions. We therefore conclude that the experimentally observed activity difference does not originate from the surface polarization following the bulk polarization, but rather from different bulk polarization directions leading to different adsorbate coverages or even surface reconstructions.

中文翻译：

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氧化铁电表面上的催化-外延应变LaTiO2N和BaTiO3用于光催化水分解。

铁电体的表面性质由于可以被施加的电场逆转的自发极化而有望用于催化。尽管一些理论研究表明，在零电势下，不同极化的铁电表面的催化活性不同，但在高电势下，对铁电表面的催化作用却很少。在与光催化实验和应用相关的这些条件下，表面通常会被氧化。使用密度泛函理论计算，我们发现，对于LaTiO2N和BaTiO3，这种氧化作用会严重影响甚至确定催化剂表面的电子性能，因此，无论本体极化如何，都会在氧释放反应的催化步骤中产生相似的反应自由能。 。这与实验研究相反，实验研究发现在氧化条件下，不同极化的催化剂表面域具有不同的活性。因此，我们得出的结论是，实验观察到的活度差异并非源于本体极化后的表面极化，而是源自不同的本体极化方向，从而导致不同的吸附物覆盖率甚至表面重构。