Researchers have improved the efficiency and economics of the water splitting reaction by completely suppressing wasteful oxygen generation — a promising advance for clean hydrogen production.
When electricity is used to split water into hydrogen and oxygen — a process called electrolysis — the hydrogen can be captured as a clean fuel or feedstock for commercially important chemicals. Oxygen, however, has low economic value and is typically released as a byproduct, even though producing it requires a significant share of the energy required for electrolysis.
A more energy-efficient alternative
To sidestep this inefficiency, the researchers adopted a hybrid approach. Unlike conventional water electrolysis, which oxidizes water to produce oxygen, their system replaces that step with glycerol oxidation, generating valuable carbon-based products.
“From an energy perspective, glycerol is easier to oxidize than water, so less electricity is needed,” says Soressa Abera Chala, a postdoctoral researcher at Johannes Gutenberg University, Mainz.
As a major byproduct of biodiesel production, glycerol is abundantly available, making the process more sustainable. Combined with the lower energy requirement, this reduces overall costs.
Another challenge in water splitting is developing an efficient catalyst to accelerate the reaction. Instead of using a traditional catalyst composed of metal nanoparticles on a carbon support, the team designed a “single-site catalyst” in which the metal atoms are dispersed individually across the surface.
Chala explains that, in traditional nanoparticle catalysts, only a fraction of the metal atoms are exposed and active, while many remain buried inside clusters.
“This can lead to unwanted reactions, such as over-breaking carbon–carbon bonds, producing undesired products, and eventually poisoning the catalyst,” he notes.
Two metals are better than one
Their “single-site catalyst” avoids these issues. Not only are the metal atoms spread out so each can participate in the reaction, but two different metals are incorporated: palladium to manage oxygen chemistry, and copper to stabilize carbon intermediates.
“Together, they reduce unwanted products and prevent catalyst poisoning, keeping the system active for longer,” says Bing Joe Hwang, professor in the Department of Chemical Engineering at National Taiwan University of Science and Technology. “This atomic-level precision allows us to control the chemistry in a way that traditional catalysts cannot.”
The catalyst also proved durable, maintaining its structure and most of its activity over 144 hours of continuous electrolysis.
Carsten Streb, a professor of chemistry at Johannes Gutenberg University, attributes this stability to several factors.
“First, the metal atoms are anchored strongly in a nitrogen-rich framework, which prevents them from moving or aggregating; second, the Cu and Pd atoms electronically stabilize each other, making the system more robust, and; third, the reaction itself avoids producing large amounts of poisoning species that could damage the catalyst.”
Under the conditions tested, the catalyst preferentially produced formate, reaching 83% efficiency, with glycolate, glycerate, and lactate making up the remainder. Formate is an industrially useful molecule used in de-icing fluids, drilling operations, and the manufacture of formic acid — a higher-value chemical with wide-ranging applications across agriculture, textiles, and chemical production.
Beyond glycerol
Streb says that their approach could also be applied to other biomass-derived molecules such as alcohols and sugars.
“This strategy has the potential to improve many types of electrochemical reactions beyond glycerol oxidation,” he says. “The principle of placing two complementary single atoms close together — one to activate oxygen species and the other to stabilize carbon intermediates — could be applied broadly.”
The researchers plan to expand their approach to other biomass-derived molecules in a future study. They will also need to evaluate their system at larger scales.
“Key challenges include scaling up the production of single-site catalysts, testing them under real industrial conditions, and performing long-term tests with practical feedstocks,” says Hwang.
Reference: Soressa Abera Chala et al., Molecular Bottom-Up Design of Single-Site Copper-Palladium Catalysts for Selective Glycerol Electro-Oxidation. Advanced Energy Materials (2026). DOI: 10.1002/aenm.202504456
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