Facile fabrication of three-dimensional carbon foam from fractionated corncob lignin

Lignin is a renewable precursor for producing carbon foams. Here, we reported a facile strategy to directly convert industrial available corncob lignin into carbon foams. Upon ethanol fractionation of the lignin, it was found different proportions of lignin possessed unique features especially with distinct thermal behaviors under the developed heating process. One of the fractionated materials lignin-60 had the Tg value of 199.23 °C and intense pyrolysis temperature of 330 °C, which could directly form lignin foam from its initial powder state without any extra additives and processing. Further, a specific heating parameter (320 °C, 5 °C min−1, 2 h for foaming stage and 1000 °C, 3.2 °C min−1 for carbonization stage) were selected for investigation. The produced carbon foam had attractive features including 0.614 g cm−3 in density, 12.59 MPa in compressive strength, and 0.0966 W m−1K−1 in thermal conductivity, etc. The formation mechanism of the produced carbon foam was also proposed, where lignin suffered a series of softening, thermal decomposition, and cross-linking during the treatment. This work provides new perspectives to corncob lignin valorization, and the produced carbon foam has potential to substitute coal/pitch-derived carbon foams.