Harvesting Hydropower via a Magnetoelastic Generator for Sustainable Water Splitting.

Ock, Il Woo; Zhao, Xun; Tat, Trinny; Xu, Jing; Chen, Jun · ACS Nano · 2022

basic_science · Level V

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Abstract

Energy consumption and the resulting climate change are the two major challenges to human sustainability. Hydrogen (H<sub>2</sub>) is a form of environmentally friendly renewable energy with an extremely high energy density of 143 MJ kg<sup>-1</sup>. Water splitting is a practical and cost-effective approach to generate H<sub>2</sub> through the decomposition of H<sub>2</sub>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<sup>-2</sup> 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<sub>2</sub> at a rate of 1.93 × 10<sup>-3</sup> mL min<sup>-1</sup>. In conclusion, this work provides a compelling method for self-powered water splitting by using flowing kinetic energy.