Jain Noopur, Roy Ahin, De Angana
Department of Biological Sciences, National University of Singapore (NUS) Singapore.
Materials Research Centre, Indian Institute of Science (IISc) Bangalore-560012 India
Nanoscale Adv. 2019 Oct 29;1(12):4938-4946. doi: 10.1039/c9na00540d. eCollection 2019 Dec 3.
Surface reducibility engineering is one of the vital tools to enhance the catalytic activity of materials. A heavy redox treatment can be utilized to affect the structure and surface of catalytic materials. Here, we choose SrTiO (STO) with a cubic perovskite structure as a system to induce oxygen vacancies by using nascent hydrogen from NaBH leading to a heavily reduced version of SrTiO (RSTO). To further understand the surface reduction and its dependence on foreign-ion (Ba) incorporation into SrTiO, SrBaTiO (SBTO) and BaTiO (BTO) are synthesized using a facile hydrothermal method. The reduced version of the pristine and mixed oxide shows distinct optical absorptions, indicating oxygen vacancy-mediated reducibility engineering. Detailed CO oxidation experiments suggest the order of activity over the as-prepared and reduced supports as STO > SBTO > BTO and RSBTO > RSTO > RBTO, respectively. The interesting observation of reversal of CO oxidation activity over STO and SBTO after reduction negates the assumption of a similar intensity of reduction on the surfaces of these oxide supports. The fundamental aspect of surface reducibility is addressed using temperature programmed reduction/oxidation (TPR/TPO) and XPS.
表面还原度工程是提高材料催化活性的重要工具之一。重度氧化还原处理可用于影响催化材料的结构和表面。在此，我们选择具有立方钙钛矿结构的SrTiO（STO）作为体系，利用NaBH产生的新生氢诱导氧空位，从而得到SrTiO的深度还原版本（RSTO）。为了进一步了解表面还原及其对SrTiO中掺入外来离子（Ba）的依赖性，采用简便的水热法合成了SrBaTiO（SBTO）和BaTiO（BTO）。原始氧化物和混合氧化物的还原版本表现出明显的光吸收，表明氧空位介导的还原度工程。详细的CO氧化实验表明，在所制备的载体和还原后的载体上，活性顺序分别为STO > SBTO > BTO和RSBTO > RSTO > RBTO。还原后STO和SBTO上CO氧化活性逆转这一有趣的观察结果否定了这些氧化物载体表面还原强度相似的假设。使用程序升温还原/氧化（TPR/TPO）和XPS来探讨表面还原度的基本问题。
