Screening of agroindustry residues for their usage as oxygen evolution reaction catalysts

The Oxygen Evolution Reaction (OER) is the limiting step of the water splitting process for the attainment of valuable hydrogen. A green and economic catalyst is hereby synthesized to reduce the OER overpotential. For the first time, a set of representative agroindustry residues were used and subjected to pyrolytic and hydrothermal treatments, fitting them into circular economy. Hydrothermally treated potato peels (PP-HC), particularly, reached 10, 50 and 100 mA/cm 2 at overpotentials of 353, 408 and 431 mV, respectively. The novel material showed good electron-transfer and small Tafel slope (52.2±0.2 mV/dec) that is explained by the presence of electronic rich bonds as confirmed by physical-chemical and electrochemical characterization. PP-HC showed an astonishingly high stability for 90 h or 8000 cyclic voltammetries, with the hydrochar suffering only slight modifications, as measured by FTIR and XPS. This innovative study opens a path to efficient and environmentally friendly green hydrogen. • The thermal treatment of agroindustry wastes favoured their electrocatalytic activity. • Significant activity differences were found depending on the raw material used. • Hydrochar of potato peels acted as a competitive alkaline OER catalyst. • Potato peels hydrochar showed high stability during 30 h and 8000 CVs. • Characterization demonstrated the significant changes on the catalyst during OER.