Anion exchange membrane (AEM) electrolysis is a promising technology to produce hydrogen through the splitting of pure water. In contrast to proton-exchange-membrane (PEM) technology, which requires precious-metal oxide anodes, AEM systems allow for the use of earth-abundant anode catalysts. Here we report a study of first-row transition-metal (oxy)hydroxide/oxide catalyst powders for application in AEM devices and compare physical properties and performance to benchmark IrO x catalysts as well as typical catalysts for alkaline electrolyzers. We show that the catalysts’ oxygen-evolution activity measured in alkaline electrolyte using a typical three-electrode cell is a poor indicator of performance in the AEM system. The best oxygen-evolution-reaction (OER) catalysts in alkaline electrolyte, NiFeO x H y oxyhydroxides, are the worst in AEM electrolysis devices where a solid alkaline electrolyte is used along with a pure water feed. NiCoO x -based catalysts show the best performance in AEM electrolysis. The performance can be further improved by adding Fe species to the particle surface. We attribute the differences in performance in part to differences in the electrical conductivity of the catalyst phases, which are also measured and reported.
Water electrolysis has benefits over other hydrogen generation technologies due to the lack of carbon footprint when integrated with a renewable source of energy. Specifically, proton exchange membrane (PEM) electrolysis is a promising technology for hydrogen generation applications because of the lack of corrosive electrolytes, small footprint, and ability to generate at high pressure, requiring only deionized water and an energy source. PEM electrolysis also produces very pure hydrogen, with none of the typical catalyst poisons that may be found in hydrogen produced from reforming. However, significant advances are required in order to in order to provide a cost-competitive hydrogen source for energy markets. This paper will discuss the current limitations and recent work by Proton Energy Systems towards reaching the DOE Hydrogen Program objective for distributed production of hydrogen from distributed water electrolysis of $3.70/gge by 2012. Status of TechnologyProton exchange membrane (PEM) electrolysis has been known for over 50 years, starting from GE technology. Proton Energy Systems is currently the world leader in manufacturing of PEM hydrogen generation products using electrolysis, with over 1300 units in the field. Pure hydrogen is used in a variety of industrial applications, including acting as a cooling fluid for power plant turbine generators, a reducing atmosphere for heat treating and semiconductor processing, and as a carrier gas for spectroscopic applications such as gas chromatography. Proton's on site hydrogen generators are costcompetitive with delivered hydrogen for these applications. However, interest in hydrogen for energy applications has increased the need to decrease capital cost and increase efficiency of electrolysis and other generation methods. PEM vs. AlkalineThere are two main types of low temperature electrolysis currently commercially available. Alkaline electrolysis uses liquid electrolyte, with high concentrations of potassium hydroxide to provide ionic conductivity and to participate in the electrochemical reactions. PEM electrolysis replaces the liquid electrolyte with a solid polymer electrolyte, which selectively conducts positive ions such as protons. The protons participate in the water-splitting reaction instead of hydroxide, creating a locally acidic environment in the cell.There are advantages and disadvantages of each system. One advantage of KOH electrolyzers is the stability of nickel and stainless steel in this environment, enabling elimination of expensive materials of construction. However, in the KOH system, the
We demonstrate the translation of a low cost, non-precious metal cobalt phosphide (CoP) catalyst from 1 cm 2 lab-scale experiments to a commercial-scale 86 cm 2 polymer electrolyte membrane (PEM) electrolyser. A 2-step bulk synthesis was adopted to produce CoP on a high surface area carbon support that was readily integrated into an industrial PEM electrolyser fabrication process. The performance of the CoP was compared head-to-head with a platinum-based PEM under the same operating conditions (400 psi, 50 °C). CoP was found to be active and stable, operating at 1.86 A.cm-2 for >1700 hours of continuous hydrogen production while providing substantial material cost savings relative to platinum. This work illustrates a potential pathway for non-precious hydrogen evolution catalysts developed in past decades to translate to commercial applications.
Lead ruthenate pyrochlore showed exceptional OER activity and stability when tested in a solid-state alkaline water electrolyzer.
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