Yao Jiani, Huang Ying, Hou Yang, Yang Bin, Lei Lecheng, Tang Xianjin, Scheckel Kirk G, Li Zhongjian, Wu Di, Dionysiou Dionysios D
Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China.
Institute of Soil and Water Resources and Environmental Science, Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China.
Chem Eng J. 2021 Feb 1;405. doi: 10.1016/j.cej.2020.126545.
Metal-free electrocatalysts have been widely used as cathodes for the reduction of hexavalent chromium [Cr(VI)] in microbial fuel cells (MFCs). The electrocatalytic activity of such system needs to be increased due to the low anodic potential provided by bacteria. In this study, graphite paper (GP) was treated by liquid nitrogen to form three-dimensional graphite foam (3DGF), improving the Cr(VI) reduction by 17% and the total Cr removal by 81% at 30 h in MFCs. X-ray absorption spectroscopy confirmed the Cr(VI) reduction product as Cr(OH). Through the spectroscopy characterizations, electrochemical measurements, and density functional theory calculations, the porous structures, edges, and O-doped defects on the 3DGF surface resulted in a higher electroconducting rate and a lower mass transfer rate, which provide more active sites for the Cr(VI) reduction. Additionally, the scrolled graphene-like carbon nanosheets and porous structures on the 3DGF surface might limit the OH diffusion and result in a high local pH, which accelerated the Cr(OH) formation. The results of this study are expected to provide a simple method to manipulate the carbon materials and insights into mechanisms of Cr(VI) reduction in MFCs by the 3DGF with exfoliated edges and O-functionalized graphene.
无金属电催化剂已被广泛用作微生物燃料电池（MFC）中还原六价铬[Cr(VI)]的阴极。由于细菌提供的阳极电位较低，此类系统的电催化活性有待提高。在本研究中，用液氮处理石墨纸（GP）以形成三维石墨泡沫（3DGF），在MFC中30小时内将Cr(VI)还原率提高了17%，总铬去除率提高了81%。X射线吸收光谱证实Cr(VI)还原产物为Cr(OH)。通过光谱表征、电化学测量和密度泛函理论计算，3DGF表面的多孔结构、边缘和O掺杂缺陷导致更高的导电率和更低的传质速率，为Cr(VI)还原提供了更多活性位点。此外，3DGF表面的卷曲状石墨烯类碳纳米片和多孔结构可能会限制OH扩散并导致局部高pH值，从而加速Cr(OH)的形成。本研究结果有望提供一种操纵碳材料的简单方法，并深入了解具有剥落边缘和O功能化石墨烯的3DGF在MFC中还原Cr(VI)的机制。
