Platinum Electrode Properties Tailored to Respond to Ultra-Low Concentrations of H2S in Gaseous Hydrogen Fuel
Hydrogen pump experiments were performed at 30oC and 100% RH using 100sccm of hydrogen gas at each electrode without any applied backpressure. The VI curves and cyclic voltammograms (CVs) before and after exposing the working electrode to H2S were measured. Figure 1 shows an increase in the H2 pumping resistance in the presence of H2S. After 4 sweeps to 1.0V were performed, some of the H2S was removed from the surface of the Pt and the H2 pump resistance indicated a partial recovery. Figure 2 illustrates the effect of the 10 ppb H2S over 5 hours and shows an increased degree of poisoning (larger increase in resistance) which can be completely recovered after 4 potential sweeps to 1.0V followed by 4 more potential sweeps to 1.4V. The observed resistance change is the direct result if H2S adsorbing onto active platinum sites preventing hydrogen dissociation from occurring. Figure 3 illustrates the decrease in the hydrogen desorption from the Pt surface due to H2S adsorption and its recovery after the H2S is desorbed at the higher potentials.
- Quesada, Calita (2014), Electrochemical Analyzer for Hydrogen Fuel, Master’s Thesis, New Mexico Tech, Socorro, NM.
- SAE J2719: Hydrogen Fuel Quality for Fuel Cell Vehicles, www.sae.org
- ISO 14687-2, Hydrogen Fuel – Product Specification, Part 2: PEM fuel cell applications for road vehicles,http://www.iso.org/iso/catalogue_detail.htm?csnumber=55083
The authors gratefully acknowledge the financial support of the DOE Fuel Cell Technologies Office and the support of Technology Development Manager Charles (Will) James, Jr.