A noble metal-free proton-exchange membrane fuel cell based on bio-inspired molecular catalysts

Hydrogen is a promising energy vector for storing renewable energies: obtained from water-splitting, in electrolysers or photoelectrochemical cells, it can be turned back to electricity on demand in fuel cells (FCs). Proton exchange membrane (PEM) devices with low internal resistance, high compactness and stability are an attractive technology optimized over decades, affording fast start-up times and low operating temperatures. However, they rely on the powerful catalytic properties of noble metalssuch as platinum, while lower cost, more abundant materials would be needed for economic viability. Replacing these noble metalsat both electrodes has long proven to be a difficult task, so far incompatible with PEM technologies. Here we take advantage of newly developed bio-inspired molecular H2 oxidation catalysts and noble metal-free O2-reducing materials, to fabricate a noble metal-free PEMFC, with an 0.74 V open circuit voltage and a 23 μW cm−2 output power under technologically relevant conditions. X-ray absorption spectroscopymeasurements confirm that the catalysts are stable and retain their structure during turnover.