Encapsulating iron nanoparticles in pea-pod-like carbon nanotubes shields the metal from the harsh chemical environment common to fuel cells. Yet it leaves the particles free to catalyze reactions that are key to generating electricity, according to researchers in China (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201204958). The finding suggests strategies for reducing the high cost of polymer electrolyte membrane (PEM) fuel cells by substituting inexpensive catalysts for platinum. Cost has been a major impediment to fuel-cell commercialization for electric cars. Researchers previously determined that some forms of iron can catalyze O2 reduction to water—the PEM fuel-cell cathode reaction—when the metal is fashioned as an electrode. Yet the acidic environment in those fuel cells and the presence of SO2 leach the metal and degrade performance, dashing hopes of exploiting inexpensive iron. Dehui Deng, Xinhe Bao, Xiulian Pan, and coworkers at Dalian Institute of Chemical Physics found a way to sidestep those problems. They report that cathodes made with the encapsulated Fe nanoparticles operate stably for several hours even in the presence of 10 ppm SO2. Reference cells generate higher electric current initially but begin to fail within minutes under those conditions, they say.