"We needed to create high, stable activity by combining one non-noble element that binds hydrogen too weakly with another that binds too strongly," said James Muckerman, the senior chemist who led the project. "The result becomes this well-balanced Goldilocks compound just right."
Unfortunately, the strongest traditional candidate for an electrocatlytic Goldilocks comes with a prohibitive price tag.
Problems with platinum
Platinum is the gold standard for electrocatalysis, combining low overpotential with high activity for the chemical reactions in water-splitting. But with rapidly rising costs already hovering around $50,000 per kilogram platinum and other noble metals discourage widespread investment.
"People love platinum, but the limited global supply not only drives up price, but casts doubts on its long-term viability," Muckerman said. "There may not be enough of it to support a global hydrogen economy."
In contrast, the principal metals in the new compound developed by the Brookhaven team are both abundant and cheap: $20 per kilogram for nickel and $32 per kilogram for molybdenum. Combined, that's 1000 times less expensive than platinum. But with energy sources, performance is often a more important consideration than price.
Turning nickel into platinum
In this new catalyst, nickel takes the reactive place of platinum, but it lacks a comparable electron density. The scientists needed to identify complementary elements to make nickel a viable substitute, and they introduced metallic molybdenum to enhance its reactivity. While effective, it still couldn't match the performance levels of platinum.
"We needed to introduce another element to alter the electronic states of the nickel-molybdenum, and we knew that nitrogen had been used for bu
|Contact: Justin Eure|
DOE/Brookhaven National Laboratory