A pinboard by
Hyeyoung Shin

Postdoc, California Institute of Technology


2D Covalent Metals: A New Materials Domain of Electrochemical CO2 Conversion

Electrochemical CO2 conversion into useful chemicals is regarded as a promising technology for a sustainable carbon cycle and easing climate change. Towards a successful deployment of the technology activating thermodynamically stable CO2, it is essential to develop catalysts with high activity, selectivity and stability. However, there has been an intrinsic limitation in the optimization of catalyst performance, a strong interdependence among binding energies of adsorbates involved during the CO2 reduction steps, which is called a scaling relationship. Recently, we have suggested that an extrinsic treatment such as the introduction of a heterogeneous boundary between metallic and non-/semi-metallic elements can be a way to pave a path to overcome the limitation, but the blending of different constituents may invoke some concerns about the catalytic stability and electrical conductivity. In this work, we offer a new idea to break the scaling relationship by using the intrinsic nature of two-dimensional (2D) covalent metals. We find that there exists a vast of 2D covalent metals with zero bandgap (i.e., good electrical conductivity), most of which are covered with non-/semi-metallic elements at the surface. Using high-throughput catalyst screening of such 61 2D covalent metals, we demonstrated an entire disruption of the scaling relation between COOH and CO binding energies, leading to the computational design of new catalysts for CO2 reduction either into CO or CH4. We also investigated the catalytic activity of the hydrogen evolution reaction (HER), a key side reaction of CO2 reduction, which was used to design catalysts not only for CO2 reduction with high selectivity, but also for HER with high activity. It should be emphasized that these finding are important because this provides insight into the way to break the strong scaling relationship limiting the catalyst performance and thereby offers a new list of materials to the field, which can be fully validated by experimental groups in the future.