Reactive sites rich porous tubular yolk-shell g-C3N4 via precursor recrystallization mediated microstructure engineering for photoreduction

• Published in: Applied catalysis. B, Environmental Vol. 253; pp. 196 - 205
• Main Authors: Tian, Na, Xiao, Ke, Zhang, Yihe, Lu, Xingxu, Ye, Liqun, Gao, Puxian, Ma, Tianyi, Huang, Hongwei
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.09.2019; Elsevier BV
• Subjects: Active sites; Carbon dioxide; Carbon nitride; Catalysis; Catalytic activity; Charge efficiency; Crystallization; Crystals; Current carriers; Engineering; g-C3N4; Hydrogen production; Isotopic labeling; Melamine; Microstructure; Microstructure engineering; Migration; Photoabsorption; Photocatalysis; Photochemistry; Photoreduction; Photoreduction activity; Precursor recrystallization; Precursors; Pyrolysis; Quantum efficiency; Reactive sites; Recrystallization; Reduction; Renewable energy; Rods; Separation; Surface charge; Yolk; g-C3N4; Reactive sites; Photoreduction activity; Precursor recrystallization; Microstructure engineering
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2019.04.036

[Display omitted] •Three novel-structured g-C3N4 were obtained via microstructure engineering.•The photoabsorption, specific surface area and charge separation are all enhanced.•The porous outer-walls and inner-cores of PTYS CN-2 have abundant reactive sites.•The apparent quantum efficiency of H2 evolution is as high as 11.8% at 420 nm.•CO production from CO2 verified by the 13C isotopic labeling increases 5.6-fold. Photoabsorption, charge separation efficiency and surface reactive catalytic sites are three critical factors in semiconductor photocatalytic process, which determine the photocatalytic activity. For bulk g-C3N4 derived from direct pyrolysis of C/N rich precursors, reactive sites distributed on the lateral edges are very scarce. In this work, we report the template-free preparation of three novel structured g-C3N4, namely, porous tubular (PT) g-C3N4, porous tubular yolk-shell (PTYS) g-C3N4, and porous split yolk-shell (PSYS) g-C3N4, by an unprecedented precursor microstructure regulation of melamine crystals in a gas-pressure mediated re-crystallization process. Enhanced photoabsorption, increased surface area, largely improved separation and migration efficiencies of photoinduced charge carriers are simultaneously realized in these g-C3N4 structures. Noticeably, selective photo-deposition test uncovers that the porous outer-walls and inner-rods of PTYS g-C3N4 are enriched by abundant reductive reactive sites, which consumedly boost the photo-reduction activity. Collectively promoted by these advantages, PTYS g-C3N4 shows not only an efficient H2 production activity with a high apparent quantum efficiency (AQE) of 11.8% at λ = 420 ± 15 nm, but also a superior CO2 reduction for CO production than bulk g-C3N4 by a factor 5.6, which is verified by the 13C isotopic labeling. This work develops precursor microstructure engineering as a promising strategy for rational design of unordinary g-C3N4 structure for renewable energy production.