Lignin porous carbon nanosheet, preparation method therefor, and application thereof in supercapacitor electrode materials

A method for preparing lignin porous carbon nanosheets, comprising:

• (a) performing “layer-by-layer self-assembly” by (1) dispersing the sulfonated lignin and oxalate in water to form a matrix solution, wherein the sulfonated lignin is at least one of the following substances:
• sodium lignosulfonate, calcium lignosulfonate and magnesium lignosulfonate in an acid pulping red liquor;
• sulfonated products of alkali lignin in an alkali pulping black liquor;
• sulfonated products of enzymolytic lignin in the biorefinery industry, or mixtures thereof, the oxalate is at least one of zinc oxalate, calcium oxalate, magnesium oxalate, ferrous oxalate, cobalt oxalate, or mixtures thereof, the weight ratio of the sulfonated lignin to the oxalate is 100:(50-150), and the total mass concentration of the sulfonated lignin and oxalate in the matrix solution is 2% to 10%;
• (2) adding ethanol to a portion of the matrix solution and separating the precipitate to obtain a lignin/oxalate composite;
• (3) adding the lignin/oxalate composite to another portion of the matrix solution, then adding ethanol to obtain an assembled lignin/oxalate composite;
• (4) repeating step (3) multiple times to obtain a layer-by-layer self-assembled lignin/oxalate composite;
• (b) carbonizing the layer-by-layer self-assembled lignin/oxalate composite;
• and
• (c) pickling the carbonized layer-by-layer self-assembled lignin/oxalate composite to form the lignin porous carbon nanosheets.