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

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.