In Situ Plasma Upcycling of Spent-Battery Graphite into Active WO3/Graphene Oxide Heterointerfaces for Efficient Hydrogen Evolution: Experimental and DFT Insights

Converting waste materials into high-value electrocatalysts through advanced synthesis technologies represents a sustainable strategy for resource recycling and clean hydrogen production. Herein, a one-step plasma-assisted electrochemical strategy, followed by ultrasonic dispersion, was developed to synthesize WO3-decorated graphene oxide heterostructures directly from spent battery graphite and tungsten rods. Among the investigated compositions, the optimized catalyst synthesized using one graphite cathode rod and three tungsten cathode rods exhibited excellent hydrogen evolution reaction (HER) performance in 0.5 M H2SO4, requiring an overpotential of 156 mV to achieve 10 mA cm–2 with a Tafel slope of 65 mV dec–1. The superior activity is attributed to strong electronic coupling at the WO3@GO heterointerface, which promotes accessible oxide–carbon interfaces and facilitates interfacial charge transfer. Density functional theory calculations further revealed interfacial charge redistribution, W 5d–O 2p–C 2p orbital hybridization, and increased electronic states near the Fermi level. The catalyst also achieved a Faradaic efficiency of 95% and sustained HER operation for 48 h with only a slight increase in overpotential and minor morphological changes after stability testing. This work demonstrates an efficient plasma-assisted route for simultaneously upcycling spent battery graphite and constructing high-performance WO3@GO heterostructures, offering a sustainable strategy for noble-metal-free hydrogen production.