How to Produce Green Hydrogen from Olivine and Seawater? By Ultrasound.

Green hydrogen is a pillar for achieving global decarbonization and the reduction of greenhouse gas emissions. Here, a new, nature-inspired process for green hydrogen production using virtually unlimited natural resources is reported. Olivine, the most abundant mineral in the Earth's upper mantle, is key to this process. It is found that 20 kHz ultrasound accelerates hydrogen production from olivine suspensions in seawater under near-ambient conditions by almost 3000 times compared to the hydrothermal process. Strong mechanical stirring does not lead to hydrogen evolution in the temperature range of 40-90 °C. The striking effect of ultrasound is attributed to acoustic cavitation, which provides depassivation of the olivine surface, fragmentation of olivine particles, and local transient heating caused by collapsing bubbles. In principle, ultrasonic activation of the olivine/seawater system enables on-demand hydrogen production.