The Controlled Synthesis of Hydrogen Electrocatalysts for Alkaline Exchange Membrane Fuel Cell and Electrolysis Applications via Chemical Vapor Deposition

The development of catalysts for the electrochemical processes of hydrogen systems (e.g., fuel cells and electrolyzer systems) continues to be an attractive area of research for renewable energy technologies. One significant challenge has been developing hydrogen catalysts suitable for alkaline environments, mainly due to the sluggish kinetics of hydrogen reactions. In alkaline environments, the kinetics are decreased by two orders of magnitude when compared to acidic environments. Chemical vapor deposition (CVD) is a conventional method used to synthesize these types of catalysts. This effort discusses extending work being done using a modified CVD process known as “Poor Man’s” CVD (PMCVD) to tailor catalyst properties and inherently further its impact in electrochemical catalyst application. PMCVD utilizes an inexpensive vacuum oven to sublime commercially available and easily synthesized metal-organic salt precursors, lowering synthesis cost while providing better control of the catalyst properties such as particle size and distribution.

Herein, we describe the various efforts conducted to characterize electrocatalysts produced via the PMCVD process to further elucidate this modified CVD method's versatility and control. Additionally, we utilize a myriad of electrochemical characterization techniques to measure the electrocatalytic activates of catalyst prepared using this modified CVD method for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) in alkaline media through half-cell reactions. The study begins with the development of rate laws and deposition mechanism for the PMCVD process facilitated by measuring particle growth as a function of metal loading. We investigate the impact varying reaction conditions have on the crystal structure of the deposited nanoparticles. We determine the PMCVD’s efficiency in alloying identical and mixed crystal structured metals through the development of bifunctional catalysts for the HOR/HER. We studied the impact varying properties of carbon supports has on the deposition method as well as how these properties impact the hydrogen kinetics. We close this work by investigating the deposition of transition metals and begin the necessary steps to elucidating the impact the addition of water has on the deposition mechanism. These results provide a clear description regarding the tuning of both physical and catalytic properties of nanoparticles produced through this deposition method.