Cobalt catalysts are used on a commercial scale to produce synthetic fuels via the Fischer-Tropsch synthesis process. As adsorbed hydrogen atoms are involved in many of the elementary reaction steps that occur on the catalyst surface during the reaction it is of interest to study how the structure of the catalyst surface affects the reactivity with di-hydrogen as well as with adsorbed hydrogen atoms. In the present study we use a combination of experimental and theoretical methods to gain insight into how the structure of a cobalt surface affects the H₂ dissociation reaction and the adsorption bond strength of the hydrogen atoms produced in this step. A comparison of the open Co(11–20) and (10–12) surfaces with the flat, close packed Co(0001) surface confirms that undercoordinated Co atoms strongly enhance the rate of H₂ dissociation. At the same time, the lower desorption temperatures found on the more open surfaces indicate that the bond strength of adsorbed hydrogen decreases, in the following order: Co(0001)>Co(10–12)>Co(11–20). DFT calculations confirm this trend, showing that hydrogen adsorbs weaker on the more open surfaces for both low and high coverages. In the context of the Fischer-Tropsch synthesis reaction we propose that step and kink sites are important for efficient H₂ dissociation. After dissociation, the higher hydrogen adsorption strength on terrace sites would promote diffusion away from the dissociation site to flat terraces where they can participate in hydrogenation reactions.

钴催化剂以商业规模用于通过费-托合成工艺生产合成燃料。由于吸附的氢原子参与了反应过程中催化剂表面上发生的许多基本反应步骤，因此有必要研究催化剂表面的结构如何影响与二氢以及与吸附的氢原子的反应性。在本研究中，我们使用实验方法和理论方法的组合来深入了解钴表面的结构如何影响H _2。解离反应和在该步骤中产生的氢原子的吸附键强度。将开放的Co（11–20）和（10–12）表面与平坦，紧密堆积的Co（0001）表面进行比较，可以证实，配位不足的Co原子会大大提高H _2的解离速率。同时，在更开放的表面上发现的较低的解吸温度表明吸附的氢的结合强度按以下顺序降低：Co（0001）> Co（10-12）> Co（11-20）。DFT计算证实了这种趋势，表明无论是低覆盖率还是高覆盖率，氢在较开放的表面上吸附的能力都较弱。在费-托合成反应的背景下，我们提出，阶跃和扭结位点对于有效的H ₂是重要的离解。解离后，平台位置上较高的氢吸附强度将促进从解离位置扩散到平坦平台，在平台上它们可以参与氢化反应。