Harvesting waste heat energy by promoting H⁺-ion concentration difference with a fuel cell structure

Energy consumption continues to rise as society develops worldwide. Meanwhile, a lot of energy is wasted in the form of heat from various devices and systems. Here we report a new power generator, which works based on a difference in H⁺-ion concentration in a fuel cell structure and produces electricity by harvesting waste heat. The device works via the following three successive processes: H₂ is oxidized at anode to H⁺ ions, the H⁺ ions then penetrate through a phosphoric acid-treated polybenzimidazole (PBI-PA) membrane and finally the H⁺ ions get reduced to H₂ at cathode with electrons coming through external circuit from the anode. This system generates electricity at a current density of 21 mA cm⁻² and a power density of 1.03 mW cm⁻² at 170 °C. The cell's thermoelectric conversion efficiency at 170 °C is 13.72%, which is higher than typical values reported for many common thermoelectric materials in low temperature regimes. This innovative approach may allow for efficient generation of electricity from waste heat.