A facile sulfur-assisted method to synthesize porous alveolate Fe/g-C3N4 catalysts with ultra-small cluster and atomically dispersed Fe sites

Biodiesel production by transesterification of waste cooking oil in the presence of graphitic carbon nitride supported molybdenum catalyst

Concerted catalytic and photocatalytic degradation of organic pollutants over CuS/g-C3N4 catalysts under light and dark conditions

Iron single atoms and clusters anchored on natural N-doped nanocarbon with dual reaction sites as superior Fenton-like catalysts

Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction (ORR) and replace Pt catalysts in fuel cells and metal-air batteries. However, it remains a challenge to increase the number of atomically dispersed active sites on these catalysts. Here we report a highly efficient impregnation-pyrolysis method to prepare effective ORR electrocatalysts with large amount of atomically dispersed Fe active sites from biomass. Two types of active catalyst centers were identified, namely atomically dispersed Fe sites and FexP particles. The ORR rate of the atomically dispersed Fe sites is three orders of magnitude higher than it of FexP particles. A linear correlation between the amount of the atomically dispersed Fe and the ORR activity was obtained, revealing the major contribution of the atomically dispersed Fe to the ORR activity. The number of atomically dispersed Fe increases as the Fe loading increased and reaching the maximum at 1.86 wt% Fe, resulting in the maximum ORR rate. Optimized Fe-N-P-C complex catalyst was used as the cathode catalyst in a homemade Zn-air battery and good performance of an energy density of 771 Wh kgZn−1, a power density of 92.9 mW cm−2 at 137 mA cm−2 and an excellent durability were exhibited.

Construction of highly dispersed iron active sites for efficient catalytic ozonation of bisphenol A

An Fe-based heterogeneous catalyst is an attractive Fenton-like catalyst for phenol synthesis due to many advantages. Nevertheless, it is challenging to control the particle size in various high-loading Fe-based materials, which limits its activity and selectivity. In this work, ultra-small Fe clusters embedded in a 3D porous interconnected open-framework g-C3N4 (denoted FeNx/CCN) were successfully fabricated by the combination of a mechanochemical reaction with one-step pyrolysis. Various characterization results showed that ultra-small Fe clusters with a high loading of 32% were uniformly distributed in the hierarchical porous carbon nitride, which offered an access for faster transportation of charge carriers. Fe sites were probably coordinated with carbon nitride by Fe2+–C≡ N–Fe3+ and Fe–Nx bonding. High-density Fe clusters could provide abundant active sites and improve the light absorption and the activating ability of H2O2. By taking advantage of semiconductor functions in combination with a rich porous structure and high-density active sites, the novel Fe cluster catalyst exhibited high activity and stability in phenol synthesis, with a maximum phenol yield of 28.1% in visible light. Combining the experimental results with Fenton chemistry, we proposed a possible photocatalytic reaction mechanism. Our work will give valuable information on the development of active metal cluster nanocatalysts for organic synthesis.

CoMoS2/rGO/C3N4 ternary heterojunctions catalysts with high photocatalytic activity and stability for hydrogen evolution under visible light irradiation

For the first time, chitin microspheres woven from nanowires with multi-scale porous structures were used as an excellent support for a catalyst of ultra-small Pd clusters. The Pd species anchored on the precursor Pre-Pd@chitin were 0.6 nm in average size, while the reduced catalyst Red-Pd@chitin featured ultra-small particles of 1.3 nm in average size. X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) demonstrated that the Pd catalyst in both oxidative and reductive states retained good dispersity and ultra-small clusters. The catalyst was tested for the hydrogenation of p-nitroanisole, exhibiting an excellent initial rate (13× that of commercial Pd/C)and excellent turnover frequency reaching 52,000 h−1. Furthermore, the catalyst could be recycled and used more than 10 times with no decay of the catalytic activity, suggesting potential industrial applications.

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

The interpretation of catalytic kinetics on supported metal catalysts typically assumes that catalytic cycles occur on static active site structures apart from local rearrangement in the coordination environment. It has been reported that certain atomically dispersed metal active sites (e.g., Cu/Chabazite zeolites and Rh/γ-Al2O3) may be mobile under relevant reaction conditions, suggesting that the active sites themselves have entropy that could be relevant to apparent reaction kinetics. Here, we systematically modify the mobility (degrees of freedom or entropy) of atomically dispersed Rhodium gem-dicarbonyls, Rh(CO)2, supported on γ-Al2O3 through functionalization of the support with straight-chain alkyl-phosphonic acids of different tail lengths ranging from 1 (methyl) to 16 carbons (hexadecyl). The restricted mobility of Rh(CO)2 results in up to a 120 °C decrease in the required temperature for CO desorption from Rh(CO)2 and 1000× increase in turn over frequency for propanal formation via ethylene hydroformylation [where Rh(CO)2 is the most abundant surface intermediate] as compared to unfunctionalized Rh/γ-Al2O3. Eyring analysis suggests that the promoted rates of CO desorption and hydroformylation are due primarily to changes in apparent activation entropy [ΔΔS‡ of up to 60 J/(mol·K)], where restricted mobility of Rh(CO)2 promotes the attempt frequency of CO desorption, which is a kinetically relevant step in hydroformylation. Further, the dependence of Rh(CO)2 reactivity on alkyl phosphonic acid tail length suggests that interactions between phosphonic acid tails far from the active site modify the rigidity of the self-assembled monolayers, such that longer tails better restricted the mobility of Rh(CO)2. This work suggests that active site entropy can influence reaction kinetics on heterogeneous catalysts when changes in active site mobility are coupled to reaction coordinates and further that controlling active site entropy can be an effective design approach to increase catalytic performance.

Low-loading Pt nanoparticles combined with the atomically dispersed FeN4 sites supported by FeSA-N-C for improved activity and stability towards oxygen reduction reaction/hydrogen evolution reaction in acid and alkaline media

A ball milling method for highly dispersed Ni atoms on g-C3N4 to boost CO2 photoreduction

Controlled Assembly of Hierarchical Metal Catalysts with Enhanced Performances

A novel photocatalytic system coupling metal-free Carbon/g-C3N4 catalyst with persulfate for highly efficient degradation of organic pollutants

Selectively catalytic hydrogenation of styrene-butadiene rubber over Pd/g-C3N4 catalyst