Carbon Surface Characteristics after Electrochemical Oxidation in a Direct Carbon Fuel Cell Using a Single Carbon Pellet and Molten Carbonates

Abstract

This study investigates carbon surface characteristics after discharge in a direct carbon fuel cell using molten carbonates. In the experiment, the top surface of a single carbon pellet is pressed on the Au electrode submerged in molten carbonates, and discharge is started at a constant current. First, the effect of the press force of the carbon pellet on voltage was investigated. With decreasing press force, voltage reduction was observed at high current, whereas the voltage remained constant at low current. Then, after the pellet was washed, its top and side surfaces after discharge were observed and analyzed. In Auger electron spectroscopy spectra, Na peaks were not detected on the carbon surface after discharge, indicating that the washing of the pellet was sufficient to remove the carbonates. On the top surface that was in contact with the electrode, surface roughness parameters decreased after discharge, indicating that the surface became smooth after discharge. In addition, changes in surface morphologies were observed after discharge; smooth hemispherical particles were observed after discharge, whereas angular particles and edges were observed before discharge. Moreover, cleavages were observed after discharge. Meanwhile, on the side surface that was not in contact with the electrode, the only observed changes were thermal cracks caused by exposure to high temperature molten carbonates. The results suggest that hemispherical particles were formed after discharge because of the combination of press force and electrochemical oxidation on the flat Au electrode, which caused edges to be smoothed during discharge. Observations indicated that the triple phase boundary (carbon, electrolyte, and anode) played an important role in changing carbon surface morphologies during discharge.

In vivo confirmation of hydration-induced changes in human-skin thickness, roughness and interaction with the environment

“…In order to analyze these changes over time, we have employed 3D laser scanning microscopy, which allowed us to observe the surface of a skin replica under high magnification and provided 3D information. [31][32][33] In this paper, we present a pilot study focused on global changes in the appearance and properties of human skin caused by exposure to water or humid conditions. In order to investigate the multifaceted response of skin to water we have examined the hydration level of the superficial stratum corneum (SSC), being the surface of skin, depth profiles of skin before and after exposure to external sources of water, the skin's water uptake abilities, the SC thickness, the real contact area against smooth CaF 2 , the skin's surface roughness, and the evolution of the dimensions of the primary lines.…”

Hydroxide electrolyte direct carbon fuel cells—Technology review

“…The type of electrolyte determines both configuration of the device and operating temperature. There are four basic types of electrolytes: molten carbonates, [11][12][13][14] solid oxide ceramics (mostly Yttria-Stabilized Zirconia), [15][16][17] water solutions of hydroxides, 18,19 and molten hydroxides. 2,[20][21][22] Since recently, cells which combine two electrolytes (molten carbonate and solid oxide), so-called hybrid DCFCs, have also been developed.…”

A SnO2-samarium doped ceria additional anode layer in a direct carbon fuel cell

“…8. The voltage decreases sharply from 1.0 V to 0.94 V at the beginning of discharge due to polarization [50]. In the next 4800 s, the voltage of the cell decreases slowly to about 0.8 V because of the gradual consumption of the active carbon fuel [51].…”