Wang Lei, Zeng Zhenhua, Gao Wenpei, Maxson Tristan, Raciti David, Giroux Michael, Pan Xiaoqing, Wang Chao, Greeley Jeffrey
Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA.
Science. 2019 Feb 22;363(6429):870-874. doi: 10.1126/science.aat8051.
Tuning surface strain is a powerful strategy for tailoring the reactivity of metal catalysts. Traditionally, surface strain is imposed by external stress from a heterogeneous substrate, but the effect is often obscured by interfacial reconstructions and nanocatalyst geometries. Here, we report on a strategy to resolve these problems by exploiting intrinsic surface stresses in two-dimensional transition metal nanosheets. Density functional theory calculations indicate that attractive interactions between surface atoms lead to tensile surface stresses that exert a pressure on the order of 10 atmospheres on the surface atoms and impart up to 10% compressive strain, with the exact magnitude inversely proportional to the nanosheet thickness. Atomic-level control of thickness thus enables generation and fine-tuning of intrinsic strain to optimize catalytic reactivity, which was confirmed experimentally on Pd(110) nanosheets for the oxygen reduction and hydrogen evolution reactions, with activity enhancements that were more than an order of magnitude greater than those of their nanoparticle counterparts.
调节表面应变是调整金属催化剂反应活性的有效策略。传统上，表面应变是由异质衬底的外部应力施加的，但这种效应常常被界面重构和纳米催化剂的几何形状所掩盖。在此，我们报告一种通过利用二维过渡金属纳米片中的固有表面应力来解决这些问题的策略。密度泛函理论计算表明，表面原子之间的吸引相互作用会导致拉伸表面应力，该应力对表面原子施加约10个大气压的压力，并产生高达10%的压缩应变，其确切大小与纳米片厚度成反比。因此，通过原子级控制厚度能够产生和微调固有应变以优化催化反应活性，这在用于氧还原和析氢反应的Pd(110)纳米片上得到了实验证实，其活性增强比相应的纳米颗粒高出一个多数量级。
