Synthesis of structure and composition controlled metal nanostructures and their application as catalyst for electroreduction of carbon dioxide

Abstract

Electrochemical $CO_2$ reduction reaction (CO2RR) has been actively investigated because it enables to decrease the $CO_2$ existing in atmosphere and to produce valuable chemicals such as hydrocarbon or alcohols. However, there are many obstacles still remains that originated from individual characteristics of catalyst materials. The numerous attempts have been reported to achieve efficient CO2RR from changing catalyst elements to modifying size, surface structure, lattice structure, and composition of catalyst. In this dissertation, we study the synthesis of structure and composition controlled metal nanostructures and their enhanced properties in applications as catalysts of CO2RR. In chapter 2, the study on the lattice structure modified heteroatom-doped Pd nanosheets (Pd NSs) was described. Solvothermal treatment of synthesized Pd NSs with DMF, $NaH_2PO_2$·x$H_2O$, and borane THF yielded H, P, and B doped Pd NSs, respectively. The prepared doped Pd NSs possess 2D Pd structures composed of modified lattice structure, resulting in enhanced CO2RR catalytic activity as well as suppressing hydrogen evolution reaction (HER), the competing reaction. Moreover, the B doped Pd NSs exhibited unique selectivity toward ethanol due to their enlarged fcc/hcp intermediate lattice structure. In chapter 3, the study on the carbon monoxide (CO) assisted synthesis of Au nanoparticles (NPs) and their applications toward CO2RR was described. Hydrothermal treatment of CO gas bubbled CTAC solutions with $HAuCl_4$ and ascorbic acid yielded Au NP synthesized with CO (Au-CO NPs). The surface structure synthesized by CO as blocking agent and the low coordination atoms on Au-CO NPs exhibited significantly desirable selectivity, selectivity toward ethanol due to their enhanced binding strength of key intermediate CO in CO2RR.