Nature-inspired sustainable graphene oxide photocatalyst for sunlight-driven H₂ production

Most carbon-based materials are traditionally derived from fossil resources, and their synthesis often requires hazardous chemicals. Developing sustainable approaches is therefore an essential method that uses renewable feedstocks, minimizes solvents and reagents. This study utilizes waste coffee silverskin (CSS), a byproduct of coffee roasting, as a renewable carbon precursor (CP) for sustainable energy applications. Herein, an eco-friendly, low-cost, and sustainable method to synthesize silverskin graphene oxide (SGO) from CSS via the ozone oxidation method is presented. This greener approach avoids the use of toxic oxidants and gives higher surface oxygenation, defect density, and hydrophilicity compared to conventional methods for graphene oxide (GO) production, thereby offering a novel and more sustainable pathway. It also enables the separation of the charge, and the extension of the interfacial interactions helps to achieve efficient solar interfacial interaction with catalysts for H2 production. Structural and compositional analysis (UV-Vis, FTIR, XRD, Raman, TGA-DSC, SEM-EDX, TEM, XPS) confirmed the presence of oxygen functionalities (C/O atomic ratio 0.31 ± 0.02) with a band gap of 2.4 eV and revealed good thermal stability. The results confirmed the successful synthesis of SGO with good catalytic activity. Its potential as a metal-free semiconductor in photocatalysis under different water matrices was indeed demonstrated splitting water into H2 gas under sunlight irradiation, achieving a hydrogen generation of 24.34 mmolg−1 2 h⁻¹ and 27.50 mmolg−1 2 h⁻¹, respectively, in ultrapure water and secondary treated wastewater. This work highlights a sustainable pathway for managing waste, promoting sustainable hydrogen production, and the potential of biomass-derived carbon catalysts for clean energy.