Methane pyrolysis-enabled production of high-value carbon fibres

Carbon fibres (CFs) are indispensable for lightweight structural engineering, yet their widespread adoption is stifled by the high cost and environmental toll of polyacrylonitrile (PAN) precursors. While substituting PAN with low-footprint alternatives such as lignin or carbon black reduces emissions, the resulting fibres typically suffer from mechanical degradation caused by poorly integrated fillers. Here we report an electrified carbon-fibre upgrading strategy that transforms low-cost, carbon-black-loaded PAN precursors into high-performance CFs by incorporating methane (CH₄)-derived carbon. By using a porous, aligned fibril network as a Joule-heating element, we achieve rapid, high-temperature pyrolysis at 1,700 K that drives CH₄ diffusion and densification of the internal microstructure. The resulting upgraded carbon fibres, comprising ~50 wt% CH₄-derived carbon, exhibit a tensile strength of 1.7 GPa and a modulus of 173 GPa. This electrified synthesis simultaneously slashes production costs to ~US$13.52 kg_CF⁻¹ and carbon footprints to ~22.39 kg_CO2 kg_CF⁻¹, offering a commercially viable pathway for high-volume industries such as automotive manufacturing. Our findings establish a circular carbon economy model that converts greenhouse gases into high-value structural materials while yielding hydrogen as a clean coproduct.