image: PVDC undergoes dehalogenation in the presence of KOH, removing Cl and H functional groups to generate the clean byproducts KCl and H2O. The dehalogenated carbon sites exhibit very high reactivity, coupling with H3BO3 to form C–B or C–O–B bonding. Thereafter, the B-doped C is obtained by inert annealing B-doped polymeric C. The SEM and HRTEM images of O-BC-2-650, which evidence a 3D interconnected porous structure and an amorphous state with short-range graphitization. Moreover, the uniform distribution of B and O in the carbon matrix. view more
Credit: ©Science China Press
Recently, Professor Zhang Guoxin from Shandong University of Science and Technology and Dr. Chang Yingna from Yancheng Teacher University published a paper entitled "Oxygenated boron-doped carbon via polymer dehalogenation as an electrocatalyst for high-efficiency O2 reduction to H2O2" in Science China Materials. In this study, a cheap, simple, and environmentally friendly method is developed for the preparation of B-doped carbon materials, and their application in the electrocatalytic synthesis of H2O2 is investigated. Boron has a lower electronegativity (2.04) than that of carbon (2.55). Thus, the B site is positively charged when situated adjacently to a C site, facilitating the chemisorption of O2 molecules. Therefore, B-doped carbon is synthesized by strategic organic dehalogenation during the synthesis process, specifically using polyvinyldichloride as the carbon source, KOH as the dehalogenating agent, and boric acid as the dopant source. Controlling the composition and morphological structure of the boron-doped carbon by systematic variation of the H3BO3 dosage and annealing temperature leads to optimized material synthesis parameters and optimal H2O2 selectivity.
Electrochemical measurements revealed that the optimal O-BC-2-650 exhibited a selectivity of 98% for the 2e− oxygen reduction to H2O2 and an average H2O2 production rate of 412.8 mmol gcat.−1 h−1 in an H-type alkaline. Density functional theory simulations indicated that the functionalization of active B sites with one oxygen atom provides the lowest Gibbs free energy change (ΔG) of 0.03 eV for the hydrogenation of * O2, while functionalization with zero or two O atoms results in much larger ΔG values (0.08 and 0.10 eV, respectively). Thus, the insertion of B–O species into a carbon matrix significantly enhances its catalytic performance for the electrochemical synthesis of H2O2. This work provides a promising low-cost electrocatalyst for the electrocatalytic synthesis of H2O2, and reveals the feasibility of B-doped carbon catalysts in practical applications, providing new ideas for the design and application of various advanced metal-free doped carbon catalysts.
See the article:
Oxygenated boron-doped carbon via polymer dehalogenation as an electrocatalyst for high-efficiency O2 reduction to H2O2
https://doi.org/10.1007/s40843-021-1891-2