Realigning the melon chains in carbon nitride by rubidium ions to promote photo-reductive activities for hydrogen evolution and environmental remediation

In situ construction of Mn3O4 cocatalyst on sodium poly(heptazine imides) for enhanced photocatalytic reduction of water and synergetic oxidation of amines

Photocatalytic hydrogen production utilizing solar energy provides a pivotal strategy for realizing a carbon-neutral society. Cocatalyst-modified semiconductor materials have emerged as promising candidates for photocatalytic applications due to their ability to facilitate the spatial separation and directional migration of photogenerated electron-hole pairs. Nevertheless, those systems often face challenges such as intricate preparation procedures and issues with non-compact recombination. Herein, we report a one-pot thermal treatment approach for synthesizing a composite of Mn3O4 nanoparticles and sodium poly(heptazine imides) (Na-PHI). Mn3O4 nanoparticles were in situ generated and embedded within the Na-PHI matrix during the sintering process. The resulted photocatalyst demonstrated significantly enhanced photoinduced charge separation efficiency, exhibiting approximately 6-fold and 3-fold improvements compared to pristine Mn3O4 and Na-PHI, respectively. The photocatalytic hydrogen evolution rate reached 14 μmol h-1, nearly 9 times that of Na-PHI (1.6 μmol h-1) in the aqueous solution of benzylamine (BA) under visible light illumination (780 nm ≥ λ ≥ 420 nm). Furthermore, the optimized Mn3O4-Na-PHI sample (Mn-Na-PHI) displayed a remarkably high photocatalytic hydrogen generation rate alongside the synchronous photo-oxidative coupling of aliphatic and aromatic amine under visible light. This work underscores the potential for rational design and synthesis of novel Na-PHI-based functional composites for sustainable energy applications.

Photoreduction of Aqueous Protons Coupling with Alcohol Oxidation on a S-Scheme Heterojunction Photocatalyst MnO/Carbon Nitride

Crystalline carbon nitride (CCN), derived from amorphous polymeric CN, is considered as a new generation of metal-free photocatalyst because of its high crystallinity. In order to further promote the photocatalytic performance of CCN, p-type MnO nanoparticles are in situ synthesized and merged with n-type CCN through a one-pot process to form p-n heterojunction. The formed interfacial electric field between the semiconductors with different work functions efficiently breaks the coulomb interaction between MnO and CCN. The prepared catalysts exhibit drastically increased photocatalytic hydrogen evolution (PHE) activity integrated with oxidation of alkyl and aryl alcohols under irradiation of visible light. In the aqueous solution of benzyl alcohol (BzOH), the hydrogen generation rate over MnO/CCN (39.58 µmol h-1) is nearly 7 times and 37 times that of pure CCN (5.76 µmol h-1) and CN (1.06 µmol h-1), respectively, combining with oxidation of BzOH to benzaldehyde. This work proposes an avenue for in situ construction of a novel 2D material-based S-scheme heterojunction and extends its application in solar energy conservation and utilization.

Cyano-Rich g-C3 N4 in Photochemistry: Design, Applications, and Prospects

Cyano-rich g-C3 N4 materials are widely used in various fields of photochemistry due to the very powerful electron-absorbing ability and electron storage function of cyano, as well as its advantages in improving light absorption, adjusting the energy band structure, increasing the polarization rate and electron density in the structure, active site concentration, and promoting oxygen activation ability. Notwithstanding, there is yet a huge knowledge break in the design, preparation, detection, application, and prospect of cyano-rich g-C3 N4 . Accordingly, an overall review is arranged to substantially comprehend the research progress and position of cyano-rich g-C3 N4 materials. An overall overview of the current research position in the synthesis, characterization (determination of their location and quantity), application, and reaction mechanism analysis of cyano-rich g-C3 N4 materials to provide a quantity of novel suggestions for cyano-modified carbon nitride materials' construction is provided. In view of the prevailing challenges and outlooks of cyano-rich g-C3 N4 materials, this paper will purify the growth direction of cyano-rich g-C3 N4 , to achieve a more in-depth exploration and broaden the applications of cyano-rich g-C3 N4 .

Novel photoelectrochemical 3D-system for water disinfection by deposition of modified carbon nitride on vitreous carbon foam

Graphitic carbon nitride (GCN) is an optical semiconductor with excellent photoactivity under visible light irradiation. It has been widely applied for organic micropollutant removal from contaminated water, and less investigated for microorganisms' inactivation. The photocatalytic degradation mechanism using GCN is attributed to a series of reactions with reactive oxygen species and photogenerated holes that can be boosted by modifying its physical-chemical structure. This work reports a successful improvement of the overall photocatalytic and electrocatalytic activities of the pristine material by thermal and chemical modification by a copolymerisation synthesis method. The copolymerisation of dicyandiamide as a precursor with barbituric acid strongly reduced photoluminescence due to the enhanced charge separation thus improving the catalyst efficiency under visible light irradiation. The material with 1.6 wt% of barbituric acid showed the best photocatalytic performance and electrochemical properties. This photocatalyst was selected for immobilisation on a conductive carbon foam, which promotes a higher electrochemical active surface area and enhanced mass transfer. This three-dimensional metal-free electrode was employed for the photoelectrochemical inactivation of two different microorganisms, Escherichia coli, and Enterococcus faecalis, obtaining removals below the detection limit after 30 min in simulated faecal-contaminated waters. This photoelectrochemical reactor was also applied to treat polluted river and urban waste waters, and the faecal contamination indicators were vastly reduced to values below the detection limit in 60 min in both cases, showing the wide applicability of this innovative photoelectrode for different types of polluted aqueous matrices.