Laser-activated potato peel-derived catalysts for enhanced oxygen evolution reaction

• Complete electrochemical cell set-up optimization favoured maximum OER performances • Laser beam usage favours functional group development on hydrochar OER catalyst • Laser radiation enhances OER due to and increase of oxygen-groups on the catalyst • Neither catalyst dose nor electrochemical activation can battle with laser treatment • High stability of laser-activated-potato peels hydrochar ensures future uses Oxygen evolution reaction (OER) is the rate-limiting step of the overall water splitting process. To promote this reaction holistic application, inexpensive, stable and environmentally friendly catalyst should be developed. This study is based on the usage of hydrothermally treated potato peels (HPP) as OER catalyst. To compete with well-performant benchmark catalysts, the unreported method of using UV laser activation (LA) was carried out. This, coupled to the water splitting process set-up optimization (electrodes selection, pH effect, catalyst loading and deposition method) as well as the use of an electrochemical activation (applying 350 consecutive voltammetry cycles) ensured the obtention of Ni foam-HPP-LA electrodes with an astonishing OER performance. Current density values of 10, 50 and 100 mA/cm 2 were obtained with low overpotentials of 360, 397 and 416 mV, respectively, and a low Tafel slope of 46.6 mV/dec revealed the quick OER kinetics. FTIR, SEM-EDS and XPS results explain these promising results, highlighting a homogeneous HPP distribution and the fact that laser and electrochemical activations enhanced functional groups presence. The optimal catalyst exhibited a high stability, requiring less than 1.4 % overpotential increase for keeping 10, 50 and 100 mA/cm 2 during 30 h each, obtaining minor physicochemical modifications, which are related to surface oxidation and molecules breakage.