Reviewed by Lexie CornerApr 28 2025
Researchers at Tohoku University have developed a surface reconstruction strategy to create durable, non-noble metal-based cathodes that improve the hydrogen evolution reaction (HER). The study was published in Advanced Energy Materials.
Characterizations of CoP|F-20 and CoP. a) Schematic synthetic illustration of CoP|F on CFP. b) SEM image of CoP|F-20 nanosheets on a single carbon fiber. Scale bar, 2 µm. c) A false-color TEM image of a typical CoP|F-20 nanosheet, showing its relative thickness. Scale bar, 100 nm. d) Atomic-resolution STEM images of CoP|F-20. Scale bar, 1 nm. Inset up right shows the corresponding FFT pattern, and down left shows crystal structure along [101̄] zone axis. e STEM-EDX elemental mapping of CoP|F-20, showing the homogeneous distribution of Co (green), P (blue), and F (red). Scale bar, 200 nm. HAADF-STEM images of CoP|F-20 f and CoP g, and corresponding integrated pixel intensities h of spacings along (201) facet. Scale bar, 1 nm. i) Co 2p and j) P 2p XPS spectra of CoP|F-20 and CoP catalysts. k XANES spectra at Co K-edge of CoP|F-20, CoP, and Co foil. l) R-space curve-fitting of EXAFS spectra of CoP|F-20 and CoP. Image Credit: Heng Liu et al.
The HER is a potential method for generating clean hydrogen fuel, which could help address climate change. However, challenges remain in scaling the reaction from laboratory settings to large-scale commercial production while maintaining low costs.
The cathodes demonstrated stable performance for over 300 hours and are expected to achieve a cost close to the US Department of Energy's 2026 hydrogen production target ($2.00 per kgH₂-1). This work could contribute to the development of efficient, non-noble metal-based cathodes for commercial proton exchange membrane (PEM) electrolyzers, potentially bridging the gap between research and industrial application.
The study addressed the inefficiency and slow kinetics of the HER by exploring transition metal phosphides (TMPs), which show promise for enhancing HER performance due to their durability and cost-effectiveness as non-precious metals. Given the typical use of noble metals for this application, the researchers aimed to fill the knowledge gap related to non-noble metals.
The team synthesized fluorine-modified cobalt phosphide (CoP) and examined its surface reconstruction and active sites using operando X-ray absorption spectroscopy (XAS) and Raman measurements. The incorporation of fluorine into the CoP1-X lattice created phosphorus (P) vacancy sites on the surface, which act as additional active sites, accelerating the HER.
This reconstructed Co is highly active, works in acidic conditions, and can maintain approximately 76 W for over 300 hours. We're getting close to an affordable method to produce fuel. The calculated cost of using this method is $2.17 per kgH2-1 - just 17 cents over the current production target set for 2026.
Heng Liu, Advanced Institute for Materials Research
The researchers found that the fluorine-modified cobalt phosphide cathode showed improved catalytic activity after undergoing surface reconstruction. The study validated these findings in both a small-scale, three-electrode laboratory setup and in commercially relevant PEM electrolyzers. These results represent progress in hydrogen evolution reaction catalyst research and may serve as a basis for the design of cost-effective, non-precious metal-based cathodes.
We're always thinking about the end goal, which is for research to make its way into everyday life. This advancement brings us one step closer to designing more realistic options for commercial PEM application.
Heng Liu, Advanced Institute for Materials Research
Journal Reference:
Wu, R., et al. (2025) Surface Reconstruction Activates Non-Noble Metal Cathode for Proton Exchange Membrane Water Electrolyzer. Advanced Energy Materials. doi.org/10.1002/aenm.202405846