Design and first-principles investigation of step-scheme (S-scheme) g-C3N4/α-MnO2 nanojunction for polystyrene photoreforming into value-added chemicals and hydrogen

Abstract

Pairing the mechanism of hydrogen evolution alongside photoreforming of plastic-based waste items offers an integrated method to produce green hydrogen fuel and recycle post-consumer plastic items concurrently to promote the development of green technology and a sustainable economy. In this work, an S-scheme heterojunction was constructed using α-MnO₂/g-C₃N₄ for the photoreformation of polystyrene (PS) to generate hydrogen (H₂), and value-added chemicals. The experimental findings revealed the α-MnO₂/g-C₃N₄ heterojunction with 10 wt % carbon nitride showing a maximum hydrogen evolution rate of 12.6 ± 2 mmol H₂ g_cat⁻¹ h⁻¹, with concurrent conversion of PS into value-added organic molecules i.e benzaldehyde, benzoic acid, toluene, benzene, carbonic acid etc. The excellent activity with the stability of the catalytic system for over 30 h of continuous reaction was ascribed to the perfect S-scheme combination with higher redox potential, rod-like morphology, compatibility, and associated chemical resistance of the catalyst, which play the key role in stabilizing the morphology and surface active sites for long time. First-Principles Investigation confirmed the compatibility between the S-scheme counterparts that helped in the improved catalytic behaviour towards photoreforming and provided the groundwork for the advancement of photocatalytic systems towards simultaneous generation of green hydrogen and reformation of waste plastic.