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Enhanced charge separation and transport efficiency induced by vertical slices on the surface of carbon nitride for visible-light-driven hydrogen evolution

Yang, Qian, Li, Zehao, Chen, ChengCheng, Zhang, Zhengguo, Fang, Xiaoming
RSC advances 2019 v.9 no.8 pp. 4404-4414
ammonium, ammonium nitrate, carbon nitride, crystal structure, electric current, hot water treatment, hydrogen bonding, hydrogen production, microstructure, photoluminescence, surface area
Numerous vertical slices with thicknesses in the range of 100–200 nm were generated from pristine bulk carbon nitride (BCN) via an ammonium nitrate (NH₄NO₃)-assisted hydrothermal treatment. Compared with the structure of BCN, the obtained novel hierarchical structure consisted of more uniform mesopores (2–14 nm) and possessed enlarged specific surface area of 64.1 m² g⁻¹. It was elucidated that both NH₄⁺ and NO₃⁻ play important roles in the formation of the vertical slices, which could not only create an acidic environment for the hydrothermal system but also form hydrogen bonds with the surface tri-s-triazine units of BCN simultaneously. It was found that the hierarchical structure exhibited enhanced crystallinity, reduced photoluminescence emission, and increased photocurrent response. Consequently, a hydrogen evolution rate of 1817.9 μmol h⁻¹ g⁻¹ was achieved by the hierarchical structure, which was 4.1 times higher than that of BCN. The hydrothermal post-treatment strategy explored in this work provides a new insight into the design and modification of polymeric carbon nitride for generating a hierarchical porous microstructure.