Sustainable preparation of waste heavy bio-oil based 3D porous carbon materials via in situ binary template activation and its application in zinc-ion hybrid capacitors

Abstract

As a liquid by-product generated during biomass pyrolysis, heavy bio-oil (HBO) possesses characteristics of high carbon content, excellent thermoplasticity, and easy polycondensation. Research on upgrading HBO into functional porous activated carbon (PAC) materials has attracted significant attention. This study developed a green and mild one-step binary green pyrolysis activation strategy, using HBO as a carbon precursor to fabricate high-quality PAC for electrochemical energy storage. By rationally tuning the activator dosage, PAC with coexisting micropores and mesopores can be directionally synthesized. Notably, BOAC-4 prepared at a HBO : activator : template mass ratio of 2 : 2 : 1 exhibits excellent specific surface area (2168 m² g⁻¹) and an ideal pore structure (31% mesoporous rate), delivering optimal electrochemical performance (325 F g⁻¹ specific capacitance at 0.5 A g⁻¹) in three-electrode systems. Meanwhile, BOAC-4 has also demonstrated excellent performance in zinc-ion hybrid capacitor systems. This study combined Raman, TEM, and GPC characterization experiments to reveal the synergistic mechanism of MgO template's spatial confinement “bridging” effect and K₂C₂O₄ activator's hierarchical “etching” pore-forming role during binary green pyrolysis activation, constructing PAC with rational micro-/mesoporous ratios and ultra-microporous properties, thereby enhancing their electrochemical performance. This study proposes a green one-step pyrolysis activation strategy for preparing PAC from HBO, offering sustainable solutions to resource recycling and environmental challenges.