NATO member is melting down 17th-century bullets to obtain a key material – and it’s doing so in record time

The shifting realities of today demand alternatives to long-standing solutions. In energy, that means moving beyond fossil fuels – a reality underscored by the current situation in Iran, which has driven up fuel prices in countries that lack domestic supply. The same urgency applies to electricity, where new approaches are gaining traction worldwide.

Solar panels are increasingly visible on homes and buildings, as people seek to generate and consume their own power. Yet innovation in this space can come from the most unexpected places – even centuries-old lead bullets. That is precisely the solution proposed by a team of researchers from the Jülich Research Center and Friedrich-Alexander University in Erlangen-Nuremberg.

Their study, titled “Recycling bullets into solar cells converts lead waste into a green energy source,” published in Cell Reports Physical Science, demonstrates how lead bullets from the 17th and 18th centuries can be repurposed into perovskite – a critical compound for solar energy production.

The ammunition used in the experiment contained carbon residues, metallic impurities and signs of oxidation after centuries of degradation. But it was precisely this compromised condition that made it suitable for the process. “In this work, we demonstrate a closed-loop approach that transforms hazardous lead waste into high-performance, high-efficiency solar cell materials,” explains Ian Marius Peters, co-author of the study.

Turning toxic waste into green energy

The key breakthrough was converting degraded lead into high-purity lead iodide, an essential ingredient in perovskite solar panels. “Perovskite solar cells rely on high-purity lead iodide, but lead is both toxic and resource-intensive to extract and refine,” Peters adds, noting that millions of tons of lead waste worldwide remain underutilized.

The process unfolded in two stages. First, the bullets were melted down and reshaped into electrodes. These were then placed in a solution of acetonitrile with dissolved iodine while an electric current was applied. From this mixture, the researchers extracted highly pure lead iodide.

This yellow powder was then used to form perovskite crystals through a technique known as inverse temperature crystallization, ultimately producing solar devices with an efficiency of 21% – a figure considered statistically on par with current standards in solar energy generation.

“This work shows that legacy toxic waste can be turned into a resource for clean energy,” Peters concludes. “By combining electrochemistry with selective purification, we demonstrate a scalable pathway toward circular materials in photovoltaics.”

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