The referenced article by Ross and Sokol in the Journal of the Electrochemical Society can be found here.
In the article, the authors study the corrosion of carbon black in an alkaline system. Specifically, they use an electrode made from acetylene black which has been labelled using carbon-14 (14C), along with mass spectroscopy to determine the current efficiencies of oxygen evolution, as well as the various corrosion processes, all using a potassium hydroxide (KOH) electrolyte. The study was carried out at different temperatures and operating potentials, as well as both with and without the addition of cobalt (II, III) oxide (CO3O4) as a catalyst.
Much of the corrosion of the carbon black in a fuel cell will take the form of carbon monoxide (CO) generation. In the normal operation of a fuel cell, the electrode is supposed to evolve gas (namely oxygen). Because of this, the observed current cannot, itself, be regarded as representative of corrosion. Instead, it is necessary to separate out the contributions from the different anodic processes. Analysis of the gas that is produced via mass spectrometry can determine the relative yields of the gases that are evolved by the electrode. For solution-phase species that are generated, another technique is necessary. The 14C labeled acetylene black, along with quantum radiochemical techniques were used to the products in the electrolyte solution.
For their experiments, the working electrode solution was isolated from the counter electrode and reference electrode solutions, with solution samples being drawn with a syringe through a rubber septum. The reference electrode that was used was a Hg/HgO electrode. For the mass spectroscopic analysis, gas was collected from the space over the electrolyte solution of the working electrode. The rate of gas evolution was calculated from the moles of gas found to be evolved, and the times between the sample collections. For the samples with cobalt oxide, transmission electron microscopy (TEM) was used to confirm the macroscopically uniform distribution of the cobalt oxide particles.
It was found that the dominant anodic processes for the acetylene black without cobalt oxide were oxygen evolution, gasification of carbon as CO, and dissolution of carbon as carbonate ions. For this plain acetylene black, there were found to be three regimes of behavior:
1. Potentials below 500 mV and temperatures below 50°C – carbon dissolution is the primary process
2. Potentials 500 – 600 mV and temperatures below 50°C – oxygen evolution and carbon dissolution occur at about equal rates
3. Above 600 mV or above 60°C – oxygen and CO evolution are dominant
The addition of cobalt oxide increased the current efficiency of oxygen evolution severalfold, but also accelerated the corrosion processes of carbon dissolution and gasification. Indeed, all three processes were seen throughout the potential region of interest. In addition to these, the cobalt oxide also catalyzed the formation of organic compounds from the carbon, which were only seen in trace amounts previously with the acetylene black sans cobalt oxide.
Source: P. N. Ross and H. Sokol. J. Electrochem. Soc., 131, 1742 (1984).