Boron‐Nitrogen‐Edged Biomass‐Derived Carbon: A Multifunctional Approach for Colorimetric Detection of H ₂ O ₂ , Flame Retardancy, and Triboelectric Nanogenerator

Abstract Enhancing the concentration and type of nitrogen (N) dopants within the Sp ² ‐carbon domain of carbon recycled from biomass sources is an efficient approach to mimic CNT, GO, and rGO to activate oxidants such as H ₂ O ₂ , excluding toxic chemicals and limiting reaction steps. However, monitoring the kind and concentration of N species in the Sp ² ‐C domain is unlikely with thermal treatments only. A high temperature for graphitization reduces N moieties, leading to low electron density. This inhibits H ₂ O ₂ adsorption and activation on catalyst surfaces. In this study, coffee waste (CW) is converted into B, N‐doped biochar (B _X Nb _Y ) using boric acid‐assisted pyrolysis (H ₃ BO ₃ mass = X and carbonization temperature = Y) under N ₂ to overcome the challenge. The B dopant regulates the concentration and type of N, provides Lewis's acid sites, and converts graphitic‐N to pyridine‐N in B _X Nb _Y . The optimized B ₃ Nb ₉₀₀ exhibits excellent colorimetric sensing performance toward H ₂ O ₂ with a low detection limit (36.9 nM) and high selectivity in the presence of many interferences and milk samples due to high pyridinic‐N and Sp ² domain sizes. Interestingly, B enhances other properties of N‐containing CW‐derived carbon and introduces self‐extinguishing and tribopositive properties. Hence, B _X Nb _Y ‐coated polyurethane foam shows excellent flame retardancy and energy harvesting performance.