Carbon vacancies enriched carbon nitride nanotubes for Pd coordination environment optimization: Highly efficient photocatalytic hydrodechlorination and CO2 cycloaddition.

The use of easily available solar energy to achieve pollutants efficient degradation and waste carbon resource CO2 utilization under mild conditions is highly desired. Herein, novel carbon vacancies enriched nanotubes graphitic carbon nitride (SCNT-500) has been successfully fabricated via melamine (MA) supramolecular hydrogen-bonded self-assembly in the presence of H2SO4. Pd NPs loaded carbon vacancies enriched carbon nitride nanotubes (Pd/SCNT-500) were used for photocatalytic chlorophenols hydrodechlorination and CO2 cycloaddition with styrene oxide. Up to 6.93 s-1 4-chlorophenol hydrodechlorination TOF and obviously improved CO2 cycloaddition efficiency could be realized with Pd/SCNT-500. The improved photocatalytic efficiency should be related to the morphology and carbon vacancies based Pd coordination environment optimization. Such as, the surface area increased nanotubes structure promoted light harvesting along with photoelectrons and holes generation; the carbon vacancies improved excited electrons capture, photoinduced carriers recombination inhibition along with substrates adsorption with electron rich Pd NPs. Mechanism studies not only demonstrated the important role of atomic hydrogen and Pd coordination environment optimization in the chlorophenols hydrodechlorination, but also confirmed the promotion ability of photogenerated electrons on CO2 cycloaddition.

Photocatalytic H2 Evolution from Ammonia Borane: Improvement of Charge Separation and Directional Charge Transmission.

Co/MII Fe layered double hydroxide (LDH) LDH photocatalysts have been designed from the aspect of employing stable half-filled Fe3+ to trap photogenerated electrons, adjusting the MII -O-Fe oxo-bridged structure to optimize the short-range directional charge transmission and intercalating oxometallate anions into the LDH to further improve light absorption along with electron-hole separation and non-noble metal Co NP loading and reduction to form a heterojunction. These LDH-based photocatalysts are employed for photocatalytic H2 evolution from ammonia borane in aqueous solution under visible light at 298 K. The photocatalytic H2 evolution activity is greatly improved through adjustment of the MII -O-Fe oxo-bridged structure and molybdate intercalation into the LDH. Turnover frequencies of up to 113.2 min-1 are achieved with Co/CoFe-Mo. Alongside the experimental results and materials characterization, capture experiments and in situ DRIFTS analysis are carried out to study the photocatalytic hydrogen production mechanism.