Hydrogen production from natural organic matter via cascading oxic-anoxic photocatalytic processes: An energy recovering water purification technology. (15th May 2020)

• Record Type: Journal Article
• Authors: Huang, Guocheng; Xiao, Zhengtao; Zhen, Weiqian; Fan, Yaxin; Zeng, Cuiping; Li, Chuanhao; Liu, Shengwei; Wong, Po Keung
• Is Part Of: Water research. Volume 175(2020)
• Publication Date: 2020-05-15
• Subjects: Natural organic matter -- Photocatalysis -- Hydrogen production -- Photocatalytic oxic-anoxic process; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.115684
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Photocatalysis provides a "green" strategy to produce the clean energy of H2 . However, the realization of efficient H2 production is usually accomplished by the consumption of electron donors, which are costly energy carriers themselves. Here, we attempted to utilize the naturally abundant humic acid (HA), a representative natural organic matter (NOM), as the source of electron donor in a cascading oxic-anoxic photocatalytic system. Results showed that degradation of HA and remarkable H2 yield (1660.9 μmol g −1 h −1 at optimal condition) were obtained successively, whereas the anoxic photocatalytic treatment of pristine HA did not improve H2 yield but substantially eliminated the H2 production and HA degradation efficiency. These phenomena suggested the preoxidation process played a vital role in counteracting the detrimental effect of HA on photocatalytic H2 production. Electrochemical measurement indicated that the preoxidized HA harbored more redox-active moieties than the untreated HA and thus leading to a higher photo-induced charge carrier separation efficiency. A variety of advanced spectroscopic analyses revealed that the photocatalytic oxic pre-treatment resulted in breakdown of chemically inert, electron mediating and chromophoric aromatic macrostructure of HA to form smaller sized oxygenated organic intermediates. These intermediates were more nucleophilic than the pristine HA and acted as sacrificial reagent in the subsequent anoxic process for boosting H2 production. This study showcases an energy recovering water remediation process and paves the way for the design of novel photocatalytic technologies for environmental application. Graphical abstract: Image 1 Highlights: Energy-recovering photocatalytic water treatments were accomplished. NOM were used as organic substrates for photocatalytic hydrogen production. Preoxidation reversed the detrimental effect of HA in H2 production. The enhanced H2 production was due to the formation of oxygenated intermediates.