Direct ink writing of high-content lignin to construct hierarchical photocatalysts for efficient reduction of 4-nitrophenol

Lignin-based carbon materials constructed by additive manufacturing are at the forefront for energy and environment research due to the abundant carbon element, low-cost, and sustainable features of lignin. Yet the uncontrollable rheological behavior and rigid structure often lead to lignin being used as an additive and the amount is very low, impeding its efficient application. Herein, we developed a low-cost direct ink writing strategy to fabricate 3D scaffolds with high lignin content (over 80 %). The printed filaments display excellent self-supporting capacity and keep intact even subjected to carbonization. As a proof of concept, the branches-leaves-inspired Pd/TiO 2 hierarchical photocatalyst was further decorated on the carbonized scaffolds for efficient catalytic reduction of 4-nitrophenol. Combined the controllable macro- and micro-structure of the scaffolds, the high light harvesting ability and specific surface area of Pd/TiO 2 hierarchical structure, the carbon-based catalyst demonstrates outstanding photocatalytic reduction activity to 4-nitrophenol, with the turnover frequency value up to 8.73 min −1 , much higher than most other carbon-based catalysts. The developed carbon-based hierarchical photocatalyst also shows good catalytic stability and reusability. This facile and scalable high content lignin 3D printing technique opens a new avenue to fabricate lignin-based carbon materials for widespread applications.