Engineering the efficient three-dimension hollow cubic carbon from vacuum residuum with enhanced mass transfer ability towards H2O2 production

Abstract Constructing efficient carbon material with enhanced mass transfer ability from vacuum residuum (VR) is of prime industrial and scientific significance. Herein, we demonstrated a one-pot synthesis of metal-free and highly symmetric hollow carbon cubes (HCCs) using cost-efficient vacuum residuum (VR) as a C/N/S source. By multi-techniques such as TEM, SEM, Raman, XPS, and XRD, it is found that the CTAB surfactant plays an important role in emulsifying and forming oil-in-water suspension particles. Subsequently, high aromatics contents in VR favor the formation of HCCs shell by graphitization on the surface of NaCl template. Notably, heavy metals (e.g., V, Ni) are not enriched in carbon skeleton due to the unique graphitization mechanism. This metal-free HCCs catalyst showed good catalytic stability and high selectivity towards direct and local electrochemical production of hydrogen peroxide (H2O2) through two-electron O2 reduction due to enhanced mass transfer ability. The results provide a novel avenue to synthesize metal-free cubic carbon material from low-cost and plentiful VR, which are essential to the design of more efficient catalysts for O2 reduction to H2O2.