Lignin-derived Ti4O7 with high specific surface area for electrocatalytic oxidation and lignin flow fuel cells

Green synthesis of high-purity Ti 4 O 7 with ultrahigh surface area using lignin. • Lignin inhibits sintering and endows Ti 4 O 7 with hierarchical porous structure. • Ti 4 O 7 @Co(OH) 2 shows excellent lignin electrocatalytic oxidation performance. • Lignin flow fuel cell reaches 5.19 mW/cm 2 peak power density. • This work promotes lignin valorization and green electrode preparation. Ti 4 O 7 is a highly promising electrode material for lignin electrocatalytic conversion and fuel cells owing to its high electrical conductivity, excellent electrochemical stability, and acid–alkali resistance. However, Ti 4 O 7 synthesized by conventional carbothermal reduction suffers from severe sintering, low specific surface area, and insufficient active sites, which hardly meet the requirements for high-efficiency electrocatalysis. This work employs lignin as both a carbon source and a pore-forming precursor. The in-situ pore generation and steric hindrance effect during lignin pyrolysis and carbonization suppress particle agglomeration in high-temperature reduction, enabling the preparation of Ti 4 O 7 with high purity and large specific surface area. Transition metal hydroxides were loaded via electrochemical deposition to construct transition metal hydroxide-modified Ti 4 O 7 -based composite electrodes, which significantly optimize surface active sites and electrocatalytic reaction kinetics. The results demonstrate that the as-prepared Ti 4 O 7 exhibits a purity of 96% and a specific surface area as high as 226.7 m 2 /g, far exceeding the product reduced by traditional carbon black. Among all Ti 4 O 7 -based composite electrodes, the Co(OH) 2 -modified sample displays the optimal lignin electrocatalytic oxidation performance, with an oxidation onset potential of 0.12 V (vs Hg/HgO) and a Tafel slope as low as 173.57 mV/dec. The assembled lignin flow fuel cell delivers a peak power density of 5.19 mW/cm 2 and a limiting current density of 25.2 mA/cm 2 , showing no obvious performance degradation after 8 h of continuous operation. This work provides experimental evidence for the green and controllable preparation of high-specific-surface-area Ti 4 O 7 , high-value utilization of lignin, and development of high-performance biomass fuel cells. Download: Download high-res image (414KB) Download: Download full-size image