Iron Oxide Synthesized with the Assistance of Açaí Berry Extract as Electrocatalysts for Water Splitting

ABSTRACT Green hydrogen is a sustainable and clean fuel that has the potential to significantly transform the global energy landscape, while also contributing to reduce the greenhouse gas emissions and mitigate the climate changes. Water electrolysis is an efficient method for the production of green hydrogen, in which water is split into oxygen and hydrogen using electricity. The oxygen evolution reaction (OER) is the most energy‐demanding and sluggish step in this process, although hydrogen evolution reaction (HER) also displays kinetics limitations, requiring the use of electrocatalysts to promote both reactions. Therefore, it is essential to explore cost‐effective and environmentally sustainable materials composed of available and low‐cost Earth‐abundant elements. This study focused on investigating iron oxide nanomaterials synthesized with the assistance of açaí berry ( Euterpe oleracea Mart .) extract as a sustainable bifunctional electrocatalysts for water splitting in alkaline conditions. Two magnetic materials were synthesized, consisting of maghemite (γ‐Fe 2 O 3 ), hematite (α‐Fe 2 O 3 ), and magnetite (Fe 3 O 4 ) phases, with nanoparticles, as small as 5 nm. Overpotentials at a current density of 10 mA cm − 2 of the order of 460 and 403 mV were achieved for OER and HER, respectively.