Exploration of Vapor Electrolysis for Chemical Transformations

Abstract

Electrolytic devices provide a carbon-free option to producing hydrogen, with many advantages such as modular, scalable design and flexibility of operating parameters (temperature, pressure, etc.).1 Typically, electrolyzers are run under conditions that require a significant amount of clean, liquid water and are run at several A/cm2. However, the solar flux limits achievable current densities to ~100 mA/cm2 and furthermore the strong solar resources are oftentimes located in regions away from a ready supply of clean water. Finally, multiphase flow in electrolyzers also complicate the transport physics and reaction kinetics. These above challenges can be surmounted through the use of vapor electrolyzer, where water vapor is split to oxygen and hydrogen directly. Vapor electrolysis has not been extensively studied due to a limitation in how much water can be supplied to the system – water electrolysis is never mass-transport limited. Some studies have shown such a device2,3 but are more proof of concept. In this talk, we discuss an experimental diagnostic study of various parameters to increase the performance of such cells that can reach 1 A/cm2. In addition, using mathematical modeling we explore the various losses endemic to this system as well as its natural advantages to utilize impure water in arid or possibly marine climates. Finally, we will discuss how the understanding gained on vapor electrolysis and gas-diffusion electrodes can be transferred to the electrochemical conversion of other gases (e.g., methane, carbon dioxide, etc.). Preliminary findings of fuel electrochemical oxidation to partial oxidation products will be discussed. Acknowledgements: J.C.F. would like to thank Dr. Michael Gerhardt, Dr. Nemanja Danilovic, and Dr. Yagya Regmi for the helpful discussions. J.C.F. also acknowledges support from National Science Foundation Graduate Research Fellowship under Grant No. DGE 1106400. This work was partially funded by the Energy & Biosciences Institute through the EBI-Shell program.