Just as smartphone batteries wear down with heavy use, catalysts—the chemical drivers of numerous chemical reactions—also deteriorate over time. This steady drop in efficiency can hamper the reactions they’re designed to accelerate, indicating when it’s time for them to be replaced.
One such catalyst-driven chemical reaction takes place in direct formic acid fuel cells, or DFAFCs. These cells are noted for their high efficiency and environmentally friendly attributes, making them ideal for portable power solutions by transforming formic acid's chemical energy directly into electricity.
Senior Principal Scientist Zhaolin Liu from A*STAR’s Institute of Materials Research and Engineering (IMRE) highlights a common setback in DFAFCs: “Palladium (Pd) electrocatalysts, commonly used in direct formic acid fuel cells, are prone to causing carbon monoxide (CO) poisoning.”
To overcome this limitation, Liu explained that incorporating hydrogen into Pd electrocatalysts to form Pd hydrides (PdHx) alters their molecular structure, which has been shown to improve the ability of these nanoparticles to boost DFAFC reactions.
Together with researchers from Tongji University, China, Liu’s team went further by experimenting with other elements like oxygen-loving nickel and phosphorus to counter CO poisoning. The researchers generated nano-sized particles that, with hydrogen incorporation, presented a more uniform structure for enhanced fuel cell performance.
(a) A schematic illustration of hydrogen particles being incorporated into a PdNiP nanoparticle. (b-c) Low-magnification transmission electron micrography (TEM) images of (b) PdNiP nanoparticles and (c) carbon-supported PdNiP-H nanoparticles. (d-e) High-resolution TEM images of (d) a single PdNiP nanoparticle and (e) PdNiP-H nanoparticle.
Liu added, “Alloying phosphorus into the catalyst introduces more amorphous structures, which serve as active sites crucial for facilitating the necessary reactions during formic acid oxidation.”
In validation experiments, the novel PdNiP-H nanoparticles achieved a peak power output which was 63.4 percent higher than systems using commercially available Pd catalysts. Additionally, PdNiP-H nanoparticles demonstrated enhanced stability against CO poisoning, thereby increasing DFAFCs’ efficiency and durability.
These new-and-improved catalysts can position DFAFCs as the preferred alternative over hydrogen fuel cells, particularly because of formic acid’s lower cost, ease of handling and green profile.
For now, the team is dedicating resources to optimising their PdNiP-H nanoparticles for industrial-scale applications. “We still observe notable a decline in performance over time, which may be linked to the partial dissolution of the alloying elements,” Liu stated.
“We plan to develop even more robust electrocatalysts by designing structures with enhanced stability, such as core-shell configurations and using more durable support materials.”
The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering (IMRE).
