Technology to reduce carbon dioxide and produce fuels is drawing attention as a solution to the problem of global warming. The development of catalysts for reducing carbon dioxide may enable one to convert carbon dioxide into a high value-added compound, decreasing the carbon dioxide concentration in the atmosphere and storing electric energy in the form of chemical energy in combination with new renewable energy sources.

Based on the basic ideas of nanochemistry, the present study was conducted to increase the efficiency of a catalytic reaction by modifying the surface structure and adjusting the element composition of noble metal-based catalysts. To increase the catalytic activity, the surface of the nanostructured catalysts was modified to have a high-indexed facet. For the elemental control, the overpotential, the essential aspect of energy efficiency, of a noble metal hybrid structure of gold and silver, was much lower than that of the catalyst prepared using only one of either gold or silver. Besides, because the gold-silver hybrid catalyst has a lower price than gold and higher stability than silver, it may help the commercialization of electrochemical carbon dioxide conversion.


Surface structure modification of nanocatalysts: noble metal nanostars and catalyst comprising the same

A simple overgrowth method was applied to the surface of icosahedral gold nanoparticles to synthesize nanostar gold particles having a high-indexed facet, which were used as a catalyst for reducing carbon dioxide. Compared to nanoparticles having a low-index (111) facet, the gold nanostars showed significantly higher carbon monoxide selectivity, current density, and catalytic activity per unit mass of catalyst. This surface overgrowth of nanocatalysts may be applied to various catalysts to improve the efficiency of electrochemical reactions.


Elemental control of nanocatalysts: hollow polyhedral carbon dioxide reduction catalysts

Both gold and silver can convert carbon dioxide to carbon monoxide through an electrochemical reaction selectively. The galvanic replacement of silver nanocubes provided Au-Ag hollow nanocubes having an Au:Ag ratio of 1:1. The Au-Ag hollow nanocubes were used as electrochemical catalysts to reduce carbon dioxide to carbon monoxides with increasing the Faradaic efficiency to 90%. In comparison with pure gold or silver, the metal alloy nanocubes significantly decreased the overpotential while maintaining the carbon monoxide selectivity. Such a relatively simple synthesis with high efficiency and low overpotential is very promising to achieve the economic feasibility of electrochemical carbon dioxide conversion. These strategies are not only active on carbon dioxide conversion but also effective for general heterogeneous reactions. Therefore, the present technologies can make a significant contribution to making large catalytic area and mass production, which are necessary for the improvement of the catalytic performance and the commercialization, respectively.


Prof. Song, Hyunjoon
2019 KI Annual Report