Proton transfer design issues

Theorists have been addressing the issue of tunneling as the predominant reaction mode in proton-transfer reactions for more than 20 years [10]. However, from an experimental perspective, there have been few significant advances relating to tunneling as a predominant reaction mode in the condensed phase at ambient temperature [20, 21]. In part, this is because design of experiments to test the predictions of the various theoretical formulations has been exceedingly difficult. 

VI. Managing Proton Reactions in Photosynthesis A. Design Issues for Proton Transfer... 

Answers to these questions are predicated on the ingenious design of new supra-molecular systems. First and foremost, well-defined model systems that allow the independent timing of proton and electron are needed some systems—notably those described in Section 4.4.10—are poised to attack this issue because they display unique spectroscopic signatures for the transfer of the electron and the proton. In addition to directly probing the sequence and rates of the two events, kinetic isotope effects for the proton and the electron transfers may be ascertained. Isotope effects have been used to infer PCET mechanisms in oxygen activation by model... 

PEM fuel cells have emerged as the most common type of fuel cell under development today. As stated above, they also are commonly referred to as proton exchange membrane fuel cells based on the key characteristic of the solid electrolyte membrane to transfer protons from the anode to the cathode. The solid electrolyte avoids problems caused by liquid electrolytes used in other systems, and the temperature range of <100°C enables rapid start-up under low temperature operation, with operation possible down to subfreezing temperatures. The lower temperature also allows a wider range of materials to be used and enables relatively easy stack design in terms of sealing issues and material selection. This type of fuel cell is the most feasible for use under transportation applications. 

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