Forked Vein Structure W/WO3- x with Dual Active Sites in W and Oxygen Vacancies to Enhance Methylene Self-Coupling for Efficient Conversion of Methane to Ethylene.

The directional conversion of methane to ethylene is challenging due to the dissociation of the C─H bond and the self-coupling of methyl intermediates. Herein, a novel W/WO3- x catalyst with the fork vein structure consisting of an alternating arrangement of WO3- x and W is developed. Impressively, the catalyst achieves an unprecedented C2 H4 yield of 1822.73 µmol g-1  h-1 , with a selectivity of 82.49%. The enhanced catalytic activity is ascribed to the multifunctional synergistic effect induced by oxygen vacancies and W sites in W/WO3- x . Oxygen vacancies provide abundant coordination of unsaturation sites, which promotes the adsorption and activation of CH4 , thus reducing the dissociation energy barrier of the C─H bond. The CH2 coupling barrier on the metal W surface is significantly lower compared to WO3 , so CH2 can migrate to the W site for coupling. Importantly, the W/WO3- x with high periodicity provides multiple ordered local microelectric fields, and CH2 intermediates with dipole moments undergo orientation polarization and displacement polarization driven by the electric field, thus enabling CH2 migration. This work opens a new avenue for the structural design and modulation of photocatalysts, and provides new perspectives on the migration of methylene between multiple active sites.

Preparation of highly dispersed Ni single-atom doped ultrathin g-C3N4 nanosheets by metal vapor exfoliation for efficient photocatalytic CO2 reduction.

Single-atom photocatalysts can modulate the utilization of photons and facilitate the migration of photogenerated carriers. However, the preparation of single-atom uniformly doped photocatalysts is still a challenging topic. Herein, we propose the preparation of Ni single-atom doped g-C3N4 photocatalysts by metal vapor exfoliation. The Ni vapor produced by calcining nickel foam at high temperature accumulates in between g-C3N4 layers and poses a certain vapor pressure to destroy the interlayer van der Waals forces of g-C3N4. Individual metal atoms are doped into the structure while exfoliating g-C3N4 into nanosheets by metal vapor. Upon optimization of Ni content, the Ni single atom doped g-C3N4 nanosheets with 2.81 wt% Ni exhibits the highest CO2 reduction performance in the absence of sacrificial agents. The generation rates of CO and CH4 are 19.85 and 1.73 µmol g-1h-1, respectively. The improved photocatalytic performance is attributed to the anchoring Ni of single atoms on g-C3N4 nanosheets, which increases both carrier separation efficiency and reaction sites. This work provides insight into the design of photocatalysts with highly dispersed single-atom.