A simple and effective mixing carbonization-activation process was developed to prepare rice hull-derived porous Si–carbon materials. The morphologies and pore structures of the materials were controlled effectively without any loading or additions at various carbonization temperatures. The structures of the samples changed from large pores and thick walls after 800 ${}^{\circ }$C carbonization to small pores and thin walls after 1000 ${}^{\circ }$C carbonization. An additional alkali activation–carbonization process led to coral reef-like structures surrounded by squama in the sample that underwent 900 ${}^{\circ }$C carbonization (Act-RH-900). This optimal material (Act-RH-900) had a large specific surface area (768 m² g⁻¹), relatively stable specific capacitance (150.8 F g⁻¹), high energy density (31.9 Wh kg⁻¹), and high-power density (309.2 w kg⁻¹) at a current density of 0.5 A g⁻¹ in 1 M KOH electrolyte, as well as a good rate performance and high stability (capacitance retention > 87.88% after 5000 cycles). The results indicated that Act-RH-900 is a promising candidate for capacitive applications. This work overcomes the restrictions imposed by the complex internal structure of biomass, implements a simple reaction environment, and broadens the potential applicability of biomass waste in the field of supercapacitors.

Porous biomass-based carbon materials with microtube arrays have been fabricated from larch waste wood by coupling green delignification and multistage carbonization. The microtube structure and pore size of the sample were effectively controlled by multistage carbonization. The obtained sample possessed a stable self-supporting microtube array structure with well-defined porosity (surface area of 945.09 m² g⁻¹) and an ideal proportion of micropores (88%). Owing to the specific porous structure and stable self-supporting system, the material showed excellent supercapacitor electrochemical performance. Remarkably, the material showed high specific capacitance (211.3 F g⁻¹ and 58.3 F cm⁻³), energy density (105.6 W h kg⁻¹), power density (900.0 W kg⁻¹), and stability (70% after 9000 cycles). Additionally, the obtained alkali activation sample, M-CMAk-800, demonstrates a splendid specific capacitance of 408.5 F g⁻¹ at a current density of 0. 5 A g⁻¹, a great rate capability retention (69%), and outstanding stability (100% after 4000 cycles) due to its high specific surface area (up to 1689.4 m² g⁻¹) and large total pore volume (up to 1.17 cm³ g⁻¹). This work realizes efficient utilization and conversion of waste wood by green delignification and a multistage carbonization process, and will open a new avenue for preparing high chemical performance self-supporting supercapacitor electrodes from biomass waste.

Here, a dual-modification strategy using KMnO₄ (potassium permanganate) and AlCl₃·6H₂O (aluminum chloride, hexahydrate) as co-modifiers to improve the Cr(VI) removal capacity of K₂CO₃ activated biochar is introduced. As a result, the dual-modified biochar with KMnO₄ and AlCl₃·6H₂O has the calculated adsorption energy of −0.52 eV and −1.64 eV for HCrO₄⁻, and −0.21 eV and −2.01 eV for Cr₂O₇²⁻. The Al₂O₃ (aluminum oxide) and MnO (manganese oxide) embedded on the surface of dual-modified biochar bring more Cr(VI) absorption sites comparing to single-modified biochar, resulting in a maximum Cr(VI) saturated adsorption capacity of 152.86 mg g⁻¹. The excellent removal performance is due to the synthetic effect of electrostatic attraction, reduction reaction, complexation reaction, and physical adsorption. The experimental results also indicated that the spontaneous adsorption process agreed well with the pseudo-second order and Langmuir models. This dual-modification strategy is not limited to the treatment of Cr(VI) with biochar, and may also be incorporated with the treatment of other heavy metals in aqueous environment.

Carbon dots have good dispersion capability, strong visible fluorescence, low toxicity, and photo-induced accepting and donating abilities. Carbon dots were obtained from biomass bacterial cellulose (BC) via one-step hydrothermal carbonization. Effects of hydrothermal time and temperature on the microstructure, fluorescence, and excitation wavelength dependent photoluminescence (PL) behavior were explored for the prepared carbon dots. The results showed that the carbon dots obtained directly from the BC (C dots) had small particle sizes (2.0 to 3.0 nm) and green luminescence behavior. Conversely, the N-doped carbon dots (N-C dots) exhibited more uniform and smaller particle sizes (approximately 1.0 nm), strong blue luminescence, acceptable fluorescence lifetime, and good stability in a wide range of pH values (2.0 to 10.0). Thus, carbon dots could serve as a fluorescent material used in high performance optical cellular imaging and highly sensitive bacterial detection.