Renewable energy sources can reduce harmful emissions, reduce dependence on fossil fuels, and improve efficiency. However, many clean energy technologies remain expensive because they rely on expensive materials such as platinum group metals (PGMs) and require efficient ways to store energy for later use.
Researchers at Washington University in St. Louis are working on a possible solution. A team led by Gang Wu, professor of energy, environmental and chemical engineering in the McKelvey School of Engineering, has developed a new catalyst designed for anion exchange membrane water electrolysis (AEMWE). This technology uses electricity from renewable sources to split water into hydrogen and oxygen, producing clean hydrogen fuel in the process.
New platinum-free hydrogen catalyst
Wu’s group focused on replacing expensive platinum-based materials commonly used in hydrogen production systems. Their approach uses renewable electricity generated from sunlight, wind, or water to separate hydrogen from water molecules.
“Transitioning from water to hydrogen is a highly desirable way to store energy for a variety of applications,” Wu said. “Hydrogen itself can be used as an energy carrier and is useful in various chemical industries and manufacturing.”
To construct the catalyst, the researchers combined rhenium phosphide (Re2P) and molybdenum phosphide (MoP). Combining the two materials created a highly effective composite material that improves the hydrogen extraction process. The rhenium component helped hydrogen attach to and be released from the catalyst surface, while molybdenum accelerated water decomposition in the alkaline electrolyte.
Durable performance for clean energy
The researchers combined the new catalyst with a nickel-iron anode and found that the system outperformed state-of-the-art cathodes, including those based on PGM materials. According to Wu, the catalyst also operated for more than 1,000 hours at industry-level current densities of 1 and 2 amps per square centimeter. This makes it one of the most durable platinum-free cathodes ever developed for anion exchange membrane water electrolyzers.
“Our findings allow us to streamline the critical role of engineering the hydrogen bond network at the catalyst/electrolyte interface when designing high-efficiency, low-cost AEMWEs,” Wu said. “Our catalyst exhibited the lowest resistance across the investigated potential range, suggesting the fastest hydrogen adsorption rate among the investigated catalysts. This newly achieved performance and durability metric makes our catalyst one of the most promising membrane electrode assemblies for practical anion-exchange membrane water electrolyzers.”
Potential for large-scale hydrogen production
Although the experiment was carried out on a laboratory scale, the researchers plan to continue studying whether the technology can be scaled up for industrial use.
This research was financially supported by the G. Wu Startup Fund at Washington University in St. Louis.
