A team of researchers led by Gang Wu created a new energy-efficient catalyst using two phosphides to split hydrogen from water. The image on the left shows the dry cathode anion-exchange membrane water electrolyzer (AEMWE), and the image on the right shows the connected dynamic hydrogen bond network.
Image Credit: Gang Wu
Scientific Frontline: Extended "At a Glance" Summary: Phosphide Heterostructure Catalysts for Hydrogen Extraction
The Core Concept: A novel, energy-efficient heterostructure catalyst designed to split water into hydrogen and oxygen using renewable electricity. This innovation provides a low-cost, highly durable alternative to traditional platinum-based materials for the production of zero-emissions hydrogen fuel.
Key Distinction/Mechanism: Unlike conventional electrolyzers that rely on expensive platinum group metals (PGM), this approach utilizes an anion-exchange membrane water electrolyzer (AEMWE) equipped with a synergistic composite of two phosphides. Rhenium phosphide optimizes hydrogen adsorption and desorption, while molybdenum phosphide accelerates water splitting to supply protons. Together, they enhance catalytic activity by effectively regulating the dynamic hydrogen-bond network at the catalyst-electrolyte interface.
Major Frameworks/Components:
- Anion-Exchange Membrane Water Electrolyzer (AEMWE): The primary electrolytic architecture utilized to separate water into its constituent elements via alkaline water electrolysis.
- Rhenium Phosphide (Re2P) & Molybdenum Phosphide (MoP): The specialized, PGM-free composite materials constituting the dry cathode.
- Hydrogen-Bond Network Regulation: The interfacial engineering mechanism that minimizes resistance and accelerates hydrogen adsorption kinetics.
- Nickel Iron Anode: The integrated counterpart to the new cathode, enabling the system to operate at industry-level current densities (1 and 2 amperes per square centimeter) for over 1,000 hours.
Branch of Science: Chemical Engineering, Materials Science, Physical Chemistry, and Renewable Energy Technology.
Future Application: Scaling up to commercial and industrial levels to enable the cost-effective, large-scale generation of green hydrogen. This hydrogen can subsequently be deployed as a primary energy carrier for the transportation sector, chemical industries, and heavy manufacturing.
Why It Matters: High storage and material costs—specifically the reliance on platinum group metals—have historically hindered the widespread adoption of green hydrogen. By demonstrating superior durability and performance without PGMs, this engineered catalyst dramatically lowers the financial barrier to sustainable hydrogen production, accelerating the transition away from fossil fuel dependence.
Using a renewable energy source has multiple benefits, including reducing harmful emissions and dependence on fossil fuels while increasing efficiency. But many of the renewable energy sources have a higher cost than fossil fuels due to the materials needed to make them usable, such as platinum group metals (PGM), and the high cost of storage.
A team of researchers led by Gang Wu, professor of energy, environmental & chemical engineering in the McKelvey School of Engineering at Washington University in St. Louis is working to change that by creating a heterostructure catalyst for an anion-exchange membrane water electrolyzer (AEMWE) that splits water into hydrogen and oxygen using electricity from renewable sources. They created the catalyst with two phosphides that gave them an efficient method to extract hydrogen, a valuable yet low-cost source of zero-emissions fuel.
Wu’s team has been looking for alternatives to catalysts that use expensive platinum group metals. In this research, their idea began with using sunlight, wind or water to create electricity that they could then use in the process to separate hydrogen from water.
“Going from water to hydrogen is a very desirable way we are able to store energy for different applications,” Wu said. “Hydrogen itself can be used as an energy carrier and is useful for different chemical industries and manufacturing.”
By combining rhenium phosphide (Re2P) and molybdenum phosphide (MoP), the team created a synergistic composite that boosted the catalytic activity in the extraction process. The rhenium is ideal for hydrogen adsorption or desorption, while molybdenum can speed up how fast the water split to supply protons in the alkaline electrolyte.
When the team integrated the catalyst with a nickel iron anode, their cathode outperformed a state-of-the-art cathode made with different materials as well as a PGM benchmark. In addition, they found it could operate at industry-level current densities of 1 and 2 amperes per square centimeter for more than 1,000 hours, making it one of the most durable PGM-free cathodes for anion-exchange membrane water electrolyzers, Wu said.
“Our findings allowed us to rationalize the critical role of engineering the hydrogen-bond network at the catalyst/electrolyte interface in designing high-efficiency, low-cost AEMWEs,” Wu said. “Our catalyst showed the lowest resistance across the studied potential range, which suggests the fastest hydrogen adsorption kinetics among the studied catalysts. This newly achieved performance and durability metrics make our catalyst one of the most promising membrane electrode assemblies for practical anion-exchange membrane water electrolyzers.”
While the team’s experiments were done on a lab scale, they plan to investigate the feasibility of using the cathode at industrial scale.
Funding: This work was financially supported by G. Wu’s startup fund at Washington University in St. Louis.
Published in journal: Journal of the American Chemical Society
Authors: Jiashun Liang, Yu Li, Chun-Wai Chang, Mingxuan Qiao, Zhenxing Feng, Chaochao Dun, Wan-Lu Li, and Gang Wu
Source/Credit: Washington University in St. Louis | Beth Miller
Reference Number: eng041426_01
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