Search

The employment of spin polarization under an external magnetic field holds great potential for the improvements of photocatalytic performance. However, owing to the huge difference in dielectric properties between ferromagnetic oxide and polymers, the photogenerated excitons with spin states are often limited to the ferromagnetic oxide wells, which leads to unsatisfactory activity. In this paper, a single-atom Co-doped C3N4 photocatalyst is successfully synthesized for photocatalytic water splitting and simultaneous oxidation of benzylamine. Under a tiny external magnetic field (24.5 mT), the hydrogen production rate could reach at 3979.0 µmol·g−1·h−1, which is about 340 times that of C3N4. Experimental results and theoretical calculations indicate that the interaction of Co d and N p orbital changes the symmetry center of C3N4, resulting in an increase in dielectric constant and spin polarization. Moreover, magnetic fields further promote parallel electron spin, and the increased number of charges with the parallel spin-down state is likely to dissociate under the action of an external magnetic field. On the other hand, the Co-N bond provides a huge built-in electric field and active site for strengthening the charge transfer and surface reaction. This work not only deepens the understanding of spin polarization, but also enriches methods to accelerate electron-hole separation. [ABSTRACT FROM AUTHOR]

Polymers are usually restricted on the high exciton binding energies and sluggish electron transfer because of the low dielectric constants. Regulating spin-polarized electrons is regarded as an attractive strategy, but often confined to the d-orbital elements. Here, the nonmetal P and N elements co-mediated the spin polarization of carbon nitrides (PCN) have been elaborately designed. The optimized PCN-3 shows an outstanding hydrogen production (22.2 mmol·g−1·h−1) coupled with selective benzylamine oxidation without using any solvent and cocatalysts, which is 200 times of original C3N4 and superior to the photocatalysts has been reported to date. Experimental and theoretical results verified that the spin-orbital coupling of N 2p and P 2p remarkably increased the parallel spin states of charge and reduced the formation of singlet excitons to accelerate exciton dissociation in carbon nitride. In addition, charge separation and surface catalysis can be significantly enhanced by the electron spin polarization of carbon nitride with the parallel arrangement, huge built-in electric field and disturbed electronic structure. Our finding deepens the insight into the charge separation and exciton dissociation in spin polarization, and offers new tactics to develop high-efficiency catalysts. [ABSTRACT FROM AUTHOR]

Carbon nitride holds a great interest in the photocatalytic hydrogen evolution integrated with selective amine oxidation (HAR) process. However, C3N4 often suffers from strong intrinsic coulombic interactions, random charge carrier transfer, and poor active sites, which lead to its unsatisfactory photocatalytic efficiency. Herein, embedded edge and bridge units in the carbon nitride framework (EBCN) were synthesized by a facile polymerization method. DFT simulation and experimental results suggest that the electron-withdrawing edges perturbed the electronic structure of C3N4 to promote the exciton dissociation as well as acted as active sites, whereas the bridge groups served as electronic channels for directional electron delivery, which enlarged the built-in electric fields and promoted interfacial carrier transfer and exciton dissociation. Consequently, EBCN exhibited an outstanding hydrogen generation rate (2296.3 μmol g−1 h−1) and high selectivity of imines (>99%) as well as good stability without using any solvent under light irradiation. This work not only paves a facile route to promote exciton dissociation and charge separation but also provides a novel catalyst for the photocatalytic H2 evolution integrated with selective amine oxidation. [ABSTRACT FROM AUTHOR]

Direct nitrogen oxidation into nitrate under ambient conditions presents a promising strategy for harsh and multistep industrial processes. However, the dynamic structural evolution of active sites in surface reactions constitutes a highly intricate endeavor and remains in its nascent stage. Here, we constructed a Bi 24 O 31 Cl 10 material with moiré superlattice structure (BCMS) for direct piezo-photocatalytic oxidation of nitrogen into nitrate. Excitingly, BCMS achieved excellent nitric acid production (15.44 mg g -1 h -1 ) under light and pressure conditions. Detailed experimental results show that the unique structure extracts the local strain tensor from the constricting Bi-Bi bond and Bi-O bond for internal structural reconstruction, which promotes the formation of electron and reactive molecule vortexes to facilitate charge transfer as well as N 2 and O 2 adsorption. Ultimately, these initiatives strengthen electron exchange between the superoxide radical and nitrogen as well as the binding strength of multiple intermediates, which swayingly adjusts the reaction path and energy barriers.