Imagine turning dirty water into plant food using only sunlight and a tiny zap of electricity — about the same amount that powers a small flashlight.

That's exactly what a team of scientists from Vienna, Austria and Suzhou, China has figured out how to do. They built a special material that transforms nitrate, a pollutant found in wastewater from farms and factories, into ammonia — the key ingredient in nitrogen fertilizers that help crops grow.

Ammonia is one of the most important chemicals in the world. Farmers rely on it to feed billions of people. But making ammonia the traditional way requires enormous amounts of energy, usually from burning fossil fuels, which contributes to climate change.

The new approach is different. Professor Günther Rupprechter and his team at TU Wien combined two materials: a layered substance called MXene (made of carbon and titanium) and tiny gold particles. When sunlight hits the MXene, it acts like thousands of microscopic antennas, capturing light energy. This energy travels to the gold particles, where the chemical magic happens — converting nitrate into ammonia.

What's really clever is that the system uses heat too. When the MXene warms up from the sunlight, that heat also gets channeled into the reaction. In most similar systems, heat is wasted. Here, it provides 57% of the chemical reactions — a complete reversal of what scientists expected.

"Nitrate molecules are polarized directly on the gold nanoparticles," explained Alexander Genest, who ran computer simulations of the process. "And this is exactly what makes the production of ammonia much easier. The amount of energy required for this is thus significantly reduced."

The catalyst produces ammonia at a rate of 2.1 moles per gram per hour — a figure the team calls "very high" and say could work in real factories. The whole process needs just 1.5 volts of electricity, roughly what aAA battery provides.

The researchers hope this approach could eventually help clean up water pollution while also producing something useful, all powered by the sun.