Ultrafine Ni-MoOx Nanoparticles Anchored on Nitrogen-Doped Carbon Nanosheets: A Highly Efficient Noble-Metal-Free Catalyst for Ammonia Borane Hydrolysis

The development of low-cost and high-efficiency catalysts for the hydrolytic dehydrogenation of ammonia borane (AB, NH3BH3) is still a challenging technology. Herein, ultrafine MoOx-doped Ni nanoparticles (~3.0 nm) were anchored on g-C3N4@glucose-derived nitrogen-doped carbon nanosheets via a phosphate-mediated method. The strong adsorption of phosphate-mediated nitrogen-doped carbon nanosheets (PNCS) for metal ions is a key factor for the preparation of ultrasmall Ni nanoparticles (NPs). Notably, the alkaline environment formed by the reduction of metal ions removes the phosphate from the PNCS surface to generate P-free (P)NCS so that the phosphate does not participate in the subsequent catalytic reaction. The synthesized Ni-MoOx/(P)NCS catalysts exhibited outstanding catalytic properties for the hydrolysis of AB, with a high turnover frequency (TOF) value of up to 85.7 min-1, comparable to the most efficient noble-metal-free catalysts and commercial Pt/C catalyst ever reported for catalytic hydrogen production from AB hydrolysis. The superior performance of Ni-MoOx/(P)NCS can be ascribed to its well-dispersed ultrafine metal NPs, abundant surface basic sites, and electron-rich nickel species induced by strong electronic interactions between Ni-MoOx and (P)NCS. The strategy of combining multiple modification measures adopted in this study provides new insights into the development of economical and high-efficiency noble-metal-free catalysts for energy catalysis applications.

Bifunctionalization of carbon nitride by incorporation of thiophene ring and polar nickel complex to promote photocatalytic activity for hydrogen evolution

Photocatalytic performance of polymeric carbon nitride (CN) is primarily restricted by limited light utilization and poor charge separation efficiency. To this end, skeleton modification strategy was adopted by attaching thiophene ring and polar nickel complex (NiL) onto CN. The obtained bifunctionalized carbon nitride (TCN-NiL) displayed obviously elevated optical absorption and photoexcited charge separation efficiency. The NiL, with polar structure, plays as active sites like cocatalyst thus exhibited platinum-like H₂ evolution activity from water splitting under visible light. The optimized photocatalytic H₂ generation rate over TCN-NiL reached 136.7 μmol·h^-1 without any cocatalyst, the highest rate reported so far in noble-metal-free CN-based catalysts, which is 5 times of that of CN loaded with 3 wt% Pt. Additionally, the maximum wavelength of performing H₂ production capacity over TCN-NiL extends to 550 nm from 450 nm of CN, suggesting an excellent visible light absorption ability. This work provides a way for modifying CN to enhance the photocatalytic activities in a noble metal free system.

Synthesis of Porous Graphitic Carbon Nitride with N3C Nitrogen Vacancy by CaCO3 Template for Improved Photocatalytic H2 Evolution

Porous graphitic carbon nitride with nitrogen vacancy (N-CN) has been successfully synthesized by a facile CaCO3 template method. The porous structure contributed to increased surface area of obtained N-CN photocatalyst....

MoP@MoO3 S-scheme heterojunction in situ construction with phosphating MoO3 for high-efficient photocatalytic hydrogen production

As important artificial photosynthesis, the construction of core-shell heterojunction materials is considered to be one of the effective strategies for designing highly active photocatalysts. Here, the Step-scheme (S-scheme) heterojunction photocatalyst is firmly grown by in situ phosphating. The calcination method uses MoO₃ nanoparticles as the substrate, and the surface of MoO₃ is phosphatized and etched gradually from the outside to the inside using the phosphine gas. The introduced phosphorus atoms can replace MoO₃ oxygen atoms to form Mo-P bonds to generate molybdenum phosphide. The interface interaction dominated by chemical bonds has a stronger interface interaction force, which can promote the interface charge transfer leading to optimizing the MoP@MoO₃ core-shell composite material, adjusting the quality of sodium hypophosphite, and phosphating MoO₃ to varying degrees, producing the best hydrogen production H₂ evolution rate is 10 000.02 μmol h^-1 g^-1. Density functional theory (DFT) calculations and a series of experiments were used to determine the S-scheme charge transfer mechanism in MoP@MoO₃. This design provides a new idea for the introduction of surface-active sites and the construction of mixed anion photocatalysts. At the same time, a new design scheme is provided for the in situ construction of S-scheme interface heterojunction materials.

TiO2/Ti3C2 intercalated with g-C3N4 nanosheets as 3D/2D ternary heterojunctions photocatalyst for the enhanced photocatalytic reduction of nitrate with high N2 selectivity in aqueous solution

TiO₂/Ti₃C₂ intercalated with g-C₃N₄ nanosheets as 3D/2D ternary heterojunctions photocatalyst was fabricated. Its performance of photocatalytic nitrate reduction was enhanced with Z-scheme heterojunction under irradiation.