HyungKuk Ju

Sustainable production of formic acid by electrolytic reduction of gaseous carbon dioxide

A tin (Sn) nanostructure has been applied to a gas diffusion electrode for the direct electro-reduction of carbon dioxide (CO2) in a zero-gap electrolytic cell. A Sn catalyst layer was evenly applied to a carbon substrate by a controlled spraying technique and the efficient catalytic conversion of gas-phase CO2 to formic acid (HCOOH) demonstrated. We observed that the overall mean faradaic efficiency towards HCOOH remained above 5.0% over the entire reduction time. In addition, due to its compact configuration and surroundings at near ambient conditions the approach described is promising in both modularity and scalability. Sustainable energy sources such as solar, wind, or geothermal electricity could be used as a power source to minimize the large-scale operating cost.

Influence of the mediating behaviour of Sn according to its particle size on a Ni/yttria-stabilised zirconia porous anode structure in a direct carbon fuel cell

Direct carbon fuel cells (DCFCs) are devices that convert the chemical energy of a carbon fuel into electrical energy with high efficiency. Although they can theoretically yield a high efficiency, DCFCs have considerable polarisation resistance, resulting from a solid-state interface between the fuel and anode surface. Here, we have employed Sn nanoparticles ( 150 μm in diameter), an interfacial resistance became alleviated with the aid of liquid-state Sn; however, the Sn microparticles tended to accumulate on the anode surface because the Sn microparticles hardly permeated into the submicron anode structure. As a result, we chose Sn nanoparticles to demonstrate the effect of the size of Sn on mediation of the Ni/YSZ (Ni/Yttria-Stabilised Zirconia) surface in this study. Unlike microparticles, the nanoparticles were observed to more deeply permeate into the Ni/YSZ pores without accumulation. Nevertheless, Sn nanoparticles are more prone to oxidation, resulting in an ionically and electronically insulating material. Therefore, the power performance of Sn nanoparticle-mounted DCFCs is, in general, lower than that of Sn microparticle-mounted DCFCs. In addition, we found that there are two possible mediation mechanisms: one is physical mediation by improving both the mass transfer and electron transfer, and the other is a Sn redox looping cycle.