Staykov Aleksandar, Tellez Helena, Druce John, Wu Ji, Ishihara Tatsumi, Kilner John
International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka, Japan.
Faculty of Engineering, Department of Applied Chemistry, Kyushu University, Fukuoka, Japan.
Sci Technol Adv Mater. 2018 Mar 2;19(1):221-230. doi: 10.1080/14686996.2018.1440136. eCollection 2018.
Surface reactivity and near-surface electronic properties of SrO-terminated SrTiO and iron doped SrTiO were studied with first principle methods. We have investigated the density of states (DOS) of bulk SrTiO and compared it to DOS of iron-doped SrTiO with different oxidation states of iron corresponding to varying oxygen vacancy content within the bulk material. The obtained bulk DOS was compared to near-surface DOS, i.e. surface states, for both SrO-terminated surface of SrTiO and iron-doped SrTiO. Electron density plots and electron density distribution through the entire slab models were investigated in order to understand the origin of surface electrons that can participate in oxygen reduction reaction. Furthermore, we have compared oxygen reduction reactions at elevated temperatures for SrO surfaces with and without oxygen vacancies. Our calculations demonstrate that the conduction band, which is formed mainly by the d-states of Ti, and Fe-induced states within the band gap of SrTiO, are accessible only on TiO terminated SrTiO surface while the SrO-terminated surface introduces a tunneling barrier for the electrons populating the conductance band. First principle molecular dynamics demonstrated that at elevated temperatures the surface oxygen vacancies are essential for the oxygen reduction reaction.
采用第一性原理方法研究了以SrO为端的SrTiO以及铁掺杂的SrTiO的表面反应性和近表面电子性质。我们研究了块状SrTiO的态密度（DOS），并将其与具有不同氧化态铁的铁掺杂SrTiO的DOS进行比较，这些不同氧化态的铁对应于块状材料内不同的氧空位含量。将所得的块状DOS与以SrO为端的SrTiO和铁掺杂SrTiO的近表面DOS（即表面态）进行比较。研究了电子密度图以及通过整个平板模型的电子密度分布，以了解可参与氧还原反应的表面电子的来源。此外，我们比较了有氧空位和无氧空位的SrO表面在高温下的氧还原反应。我们的计算表明，主要由Ti的d态形成的导带以及SrTiO带隙内的Fe诱导态仅在以TiO为端的SrTiO表面上可及，而以SrO为端的表面为填充导带的电子引入了一个隧穿势垒。第一性原理分子动力学表明，在高温下表面氧空位对于氧还原反应至关重要。
