Hierarchically porous biochar for supercapacitor and electrochemical H2O2 production

[Display omitted] •Hierarchically porous biochar was prepared from metal-rich nutshell.•The biochar exhibited a good capacitive performance in neutral electrolyte.•The biochar with sp3-C exhibited a good catalytic H2O2 production activity. Although biochar is widely recognized as a multifunctional material, developing high-performance carbon materials from biochar for both energy and environmental applications remains challenging. In this work, torreya grandis inner-shell, a widespread lignocellulosic biomass waste, was used to synthesize hierarchically porous carbon materials via a designed carbonization/activation approach. The prepared biochar exhibited excellent energy storage performance in 1 M Na2SO4 with a large capacitance, high-rate capability, and favorable stability (97% capacitance retention after 5000 cycles). The fabricated carbon materials also exhibited good catalytic activity toward electrosynthesis of hydrogen peroxide from oxygen reduction. The production of H2O2 was as high as 61.3 mg L−1h−1 at −0.6 V and pH 3.0, which was used for efficient degradation of organic pollutants (rhodamine B and phenol) in an electro-Fenton system. This work provides an efficient and low-cost approach for the carbonization/activation of waste biomass to obtain the hierarchical porous biochar for clean energy storage and environmental application.