Harvesting Hydropower via a Magnetoelastic Generator for Sustainable Water Splitting.

Energy consumption and the resulting climate change are the two major challenges to human sustainability. Hydrogen (H 2 ) is a form of environmentally friendly renewable energy with an extremely high energy density of 143 MJ kg -1 . Water splitting is a practical and cost-effective approach to generate H 2 through the decomposition of H 2 O by electrolysis with an external power supply. Herein, we introduce a compelling platform technology for self-powered water splitting by using a soft magnetoelastic generator to convert hydropower into electricity as a sustainable power supply for electrolysis. At a rotating speed of 469 rpm, the hydropower harvester is able to convert flowing kinetic energy into electricity and produce a high current density of 2.99 mA cm -2 at a low resistance of 60 Ω. The magnetoelastic generator is intrinsically waterproof since the magnetic field can penetrate the water molecules. As a demonstration, the device maintained a stable electrical output even in underwater situations after over 7,000 cyclic operations. The generated electricity from hydropower could produce H 2 at a rate of 1.93 × 10 -3 mL min -1 . In conclusion, this work provides a compelling method for self-powered water splitting by using flowing kinetic energy.