Photoelectrocatalytic Green Hydrogen Production from Coconut Water Waste Using Carbon-MgO Nanocomposite-Modified Electrodes

Abstract

Hydrogen is considered a promising alternative to fossil fuels; however, conventional water electrolysis requires substantial energy input and may have limited environmental efficiency. This study investigates the synthesis of carbon–magnesium oxide (C–MgO) nanocomposites mediated by red dragon fruit (Hylocereus polyrhizus) peel extract for enhancing green hydrogen production from coconut water waste through photoelectrocatalysis. The nanocomposite was synthesized using a hydrothermal method and characterized using UV–Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). UV–Vis analysis indicated good optical stability, with a main absorption band at 400–500 nm and a band gap energy of 2.48–2.66 eV, indicating suitability for visible-light-driven photoelectrocatalysis. FTIR analysis confirmed the presence of –OH, C=C, C=O, and Mg–O functional groups. XRD results revealed the characteristic diffraction pattern of C–MgO with a cubic crystal structure and an average crystallite size of 17.41 nm. These physicochemical properties contributed to improved photoelectrocatalytic hydrogen production. Conventional electrolysis of coconut water produced hydrogen at a rate of 0.3636 mL/min, whereas photoelectrocatalysis using a C–MgO 1:3-modified electrode achieved a production rate of 3.1489 mL/min. The incorporation of carbon and MgO into the electrode modifier increased the hydrogen production rate by 766.03% compared with conventional electrolysis. Overall, the results demonstrate that the biosynthesized C–MgO nanocomposite effectively enhances visible-light-driven photoelectrocatalytic hydrogen production from coconut water waste, offering a promising approach for waste valorization and sustainable green hydrogen generation.