Highly energy-efficient hydrogenolysis of high-density polyethylene via hydrogen nonthermal plasma reaction engineering

Abstract

The global surge in synthetic plastic production has resulted in massive waste accumulation and environmental pollution, with most polyolefins ending up in landfills and only a small fraction being downcycled into low-value products. While chemical upcycling offers a sustainable alternative, conventional approaches such as pyrolysis and catalytic hydrogenolysis suffer from slow kinetics, high energy demands, and reliance on costly catalysts. Here, we report the first demonstration of a highly energy-efficient, noncatalytic hydrogenolysis process for high-density polyethylene (HDPE) using dielectric barrier discharge (DBD) nonthermal plasma (NTP) operated under ambient temperature and pressure. Through integrated reactor and reaction engineering, we achieve complete conversion of both pure and real waste HDPE within minutes, producing valuable C₁–C₄ light hydrocarbons and waxes. Mechanistic investigations reveal that optimized plasma–polymer interactions and precisely tuned plasma species energetics and density are critical for maximizing energy efficiency. The system reaches a record output-to-input energy ratio of 8.2 and an electricity cost as low as 2.7 cents per kg of HDPE, far surpassing previously reported NTP-based hydrogenolysis approaches. Notably, waste HDPE yields even higher output energy, confirming the robustness and practical relevance of the process. This work establishes a scalable, low-energy, and catalyst-free platform for sustainable plastic upcycling, offering a transformative and economically viable pathway for converting polyolefin waste into valuable chemical products using ambient, electricity-driven plasma technology.