水是这个行星上最常见也是最重要的物质之一。它不仅和人们的日常生活密切相关，而且在科学研究中扮演着非凡的角色。作为有前途的清洁能源，燃料电池的主要反应产物是水。电极反应的速率决定于燃料电池阴极的氧还原反应。通常在使用一段时间之后，燃料电池的铂电极表面会覆盖上一层主要成分为beta-PtO2的氧化物薄膜。我们将应用第一性原理计算研究水在这层氧化物表面的吸附结构，beta-PtO2对氧还原反应的活性，以及水在氧还原反应中扮演的角色。我们还将研究表面缺陷对水吸附结构以及氧还原反应的影响。我们的工作将从原子尺度上建立起在beta-PtO2表面发生的氧还原反应的微观图像。基于这些研究结果评估水和氧化物薄膜的存在对电极反应的影响，为改善燃料电池的性能提供理论支持。

Water is one of the most ubiquitous and important substances of this planet. It not only relates closely to people's life, but also plays a nontrivial role in scientific research. As a promising clean energy resource, a fuel cell produces water as the main reaction product. The rate of electrode reactions is determined by the oxygen reduction reaction (ORR) that takes place at the cathode of a fuel cell. Generally, after some time of application, the platinum (Pt) electrodes are covered by thin films of Pt oxides whose major component is beta-PtO2. Using first-principles calculations, we will study the adsorption structures of water molecules on the surfaces of beta-PtO2, the activity of beta-PtO2 for ORR, as well as the role of water in ORR. We will also study the effects of surface defects on the adsorption structures of water and ORR. Our work will establish a microscopic picture from the atomic level for the ORR that takes place on the beta-PtO2 surfaces. Based on the results, we can evaluate the influences of the presence of water and Pt oxide thin films on the electrode reactions, which would provide theoretical supports for improving the performance of fuel cells.