Nanoscale zerovalent iron synthesized using borohydride (B-NZVI) has been widely applied in environmental remediation in recent decades. However, the contribution of boron in enhancing the inherent reactivity of B-NZVI and its effectiveness in removing hexavalent chromium [Cr(VI)] have not been well recognized and quantified. To the best of our knowledge, herein, a core–shell structure of B-NZVI featuring an Fe–B alloy shell beneath the iron oxide shell is demonstrated for the first time. Alloyed boron can reduce H+, contributing to more than 35.6% of H2 generation during acid digestion of B-NZVIs. In addition, alloyed B provides electrons for Fe3+ reduction during Cr(VI) removal, preventing in situ passivation of the reactive particle surface. Meanwhile, the amorphous oxide shell of B-NZVI exhibits an increased defect density, promoting the release of Fe2+ outside the shell to reduce Cr(VI), forming layer-structured precipitates and intense Fe–O bonds. Consequently, the surface-area-normalized capacity and surface reaction rate of B-NZVI are 6.5 and 6.9 times higher than those of crystalline NZVI, respectively. This study reveals the importance of alloyed B in Cr(VI) removal using B-NZVI and presents a comprehensive approach for investigating electron pathways and mechanisms involved in B-NZVIs for contaminant removal.
Yang Qiang,Liu Jiali,Yan Dejian,Liu Jikai,Luo He’an
Abstract Boron-rich alloy boron suboxide (B 6 O) as a novel metal-free photocatalyst was recently explored for photocatalytic CO 2 reduction and water splitting. However, to broaden the potential applications of B 6 O in the field, further improving its activity and understanding its fundamental chemical properties are essential. Herein, transition metal doping (Cr or Co) is designed to engineer the band structure of B 6 O via a solid state reaction. The valence band edge of Cr or Co doped B 6 O is proposed to be more positive than that of pristine B 6 O while the original conduction band of B 6 O is not much influenced by doping, contributing to the better light harvesting ability and lower charge recombination rate of doped B 6 O. The photocatalytic and photoelectrochemical (PEC) performances of doped B 6 O were therefore remarkably enhanced. The apparent quantum yields (AQY) of 20 wt% Cr or Co doped B 6 O are much higher than that of pristine B 6 O. In addition, the 20 wt% Cr doped B 6 O exhibits the best electrical conductivity and photocatalytic performance compared with the Co doped B 6 O and pristine B 6 O. The present work demonstrates a facile and effective strategy to engineer the band structure and reduce the charge migration resistance of B 6 O. Graphic Abstract
危险品化学品经营许可证（带存储）