First-Principles Insights Into Surface Processes: From Electrochemical Transformations To Mechanochemical Molecular Motion

Surface chemistry has wide-ranging applications, spanning from heterogeneous catalysis and optoelectronics to the realization of new chemical processes. This dissertation provides first-principles insights into two specific domains: a) role of surface reconstruction and multi-component active sites in heterogeneous catalysis, and b) geometry-driven mechanochemical molecular motion and application of such in catalysis. Electrocatalytic CO2 conversion toward value added chemicals and green H2 production constitute two major cornerstones of a future based on sustainable energy technologies. Nickel phosphides (NixPy) are a class of metallic materials that are made from earth abundant elements and therefore can be deployed as cost-effective electrocatalysts. First, we show how one can leverage the role of surface reconstructions in NixPy under electrocatalytic conditions to perform selective H2 evolution and CO2 conversion. We unravel the catalytic engines of NixPy surfaces and establish their structure-property relationships. Furthermore, we design a multi-component active site for alkane dehydrogenation (ADH) which is an integral reaction of the chemical industry. Via first-principles calculations, we demonstrate that a dual atom alloy, i.e., a heterodimer active site on a host metal, with a metal carbonyl molecular additive can help overcome several limitations of ADH. On another front, we predict that geometric effect, specifically curvature, can be harnessed to achieve directional molecular motion of adsorbates on two-dimensional materials such as graphene. By envisioning these molecular walkers as carriers of charge and disruptors of local bonding, our findings offer a novel approach to tune the electronic structure of two-dimensional materials for crucial applications. Furthermore, we show that directional motion of non-covalently attached molecules can be exploited to create binding sites with tunable chemisorption energy on curved graphene. Therefore, we predict that mechanochemical molecular motion can help perform dynamic catalysis and has the potential to overcome fundamental limitations in heterogeneous catalysis.