Ka-Fu Yung

Spin-state plays a crucial role in defining the electronic structure and catalytic reactivity of transition metal catalysts. However, precise manipulation of spin states is challenging, and their impact on catalytic mechanisms remains poorly understood. Here, we show that the curvature of carbon nanotubes (CNTs) tunes the spin state of cobalt phthalocyanine (CoPc) anchored on CNTs, thereby affecting the activity and selectivity in the electroreduction of nitric oxide (NORR) to ammonia. As the CNT diameter falls below 3 nm, the Co²⁺ center spontaneously transitions from a low-spin (LS) to a high-spin (HS) state. Density functional theory calculations and in situ spectroscopic measurements show that the HS state weakens the N=O bond and promotes bent *NO, which favors NH₃ generation. As a result, the optimized catalyst achieves a high partial current density with a Faradaic efficiency of >90% at -0.5 V versus the reversible hydrogen electrode (RHE), while maintaining good stability. This work highlights spin-state engineering via support curvature for selective electrochemical transformations.

Stable zeolites with extra-large pores and nano dimensions that are capable of processing large molecules are in high demand but have been difficult to produce. Their complex structures and nanoscale crystal sizes present challenges for analysis using conventional x-ray diffraction techniques, leading to inefficiencies in material development. We report NJU120-1 and NJU120-2, two robust and fully connected aluminosilicate nano zeolites featuring interconnected channel systems with extra-large 22-ring pores. NJU120-1 is a nanosheet with only about 8-nanometer thickness, corresponding to 1.5 unit cells, and NJU120-2 is a nanorod with 50 by 250 nanometer dimensions. Their synthesis optimization was greatly accelerated through rapid structure determination with MicroED, revealing their multidimensional pore structures. Their very large largest-free-sphere diameters of approximately 1.2 nanometers coupled with nano morphologies enabled catalytic cracking of large molecules.

Single atom catalysts (SACs) show exceptional molecular adsorption and electron transfer capabilities owing to their remarkable atomic efficiency and tunable electronic structure, thereby providing promising solutions for diverse important processes including photocatalysis, electrocatalysis, thermal catalysis, etc. Consequently, SACs hold great potential in the detection and degradation of pollutants present in contaminated gases. Over the past few years, SACs have made remarkable achievements in the field of contaminated gas detection and purification. In this review, we first provide a concise introduction to the significance and urgency of gas detection and pollutant purification, followed by a comprehensive overview of the structural feature identification methods for SACs. Subsequently, we systematically summarize the three key properties of SACs for detecting contaminated gases and discuss the research progress made in utilizing SACs to purify polluted gases. Finally, we analyze the enhancement mechanism and advantages of SACs in polluted gas detection and purification, and propose strategies to address challenges and expedite the development of SACs in polluted gas detection and purification.

The charge screening caused by ionic strength always brings about negative effects. Poly(hexamethylene biguanide) (PHMB) was found to possess screening-enhanced effect and could effectively overcome charge screening limitations. However, the mechanism of action is unknown. We hereby combine flocculation experiments and theoretical simulations through density functional theory and molecular simulation to unravel the screening-enhanced effect. The biguanide groups of PHMB serve as primary active adsorption sites and activate the hydrogen atom in neighboring alkyl chains, which raises the binding possibility in the flocculation process. Electrolyte ions hardly affect the weak interactions but increase PHMB inter-segment stacking absorption and promote the hydrophobic effect of flocculation complexes, thereby enhancing the flocculation performance. The results suggest that the binding forces primarily arose from dispersion-dominant weak interactions, indicating a weak-interaction-dependent mechanism. This study may lay a solid foundation for developing screening-enhanced materials with the powerful capabilities of anti-charge screening limitations for specific application scenarios.

An eco-friendly two-step synthetic method for synthesizing Pd@PdPt/CNTs nanoparticles was introduced and studied for the methanol oxidation reaction. The Pd@PdPt alloy core-shell structure was synthesized by preparing a surfactant-free monodispersed Pd/CNTs precursor through the hydrolysis of tetrachloropalladate (II) ion ([PdCl₄]²⁻) in the presence of carbon nanotubes (CNTs) and the subsequent hydrogen reduction and followed by a galvanic replacement reaction. This method opens up an eco-friendly, practical, and straightforward route for synthesizing monometallic or bimetallic nanoparticles with a clean surfactant-free electrocatalytic surface. It is quite promising for large-scale preparation. The Pd@PdPt/CNTs electrocatalyst demonstrated a high specific mass activity for methanol oxidation (400.2 mAmg_Pt⁻¹) and excellent stability towards direct methanol oxidation compared to its monometallic counterparts.

Occurrence of large-scale harmful algal blooms (HABs) in our reservoirs and water bodies threaten both quality of our drinking water and economy of aquaculture immensely. Hence, rapid removal of HAB biomass during and after a bloom is crucial in protecting the quality of our drinking water and preserve our water resources. We reported here a rapidly deployable algae cleaning system based on a high-capacity high-throughput (HCHT) spiral blade continuous centrifuge connected with inlet and effluent water tanks and a series of feed-in and feed-out pumps as well as piping, all fitted into a standard 20 feet metal shipping container. The system separates algal biomass from algae-laden water with a maximum flow rate of 4000 L/h and a centrifugal force of 4500× g. Cells collected by the system are still intact due to the low centrifugal force used. We showed that after HCHT centrifugation, cellular contents of HAB biomass were not found in the effluent water, and hence, could be discharged directly back to the water body. Furthermore, the addition of flocculants and chemicals prior to the separation process is not required. The system could operate continuously with proper programmed procedures. Taken overall, this system offered a much better alternative than the traditional flocculation- and sonication-based methods of HAB removal in a freshwater environment. This deployable system is the first of its kind being built and had been field-tested successfully.

A novel mesoporous Zn/MgO hexagonal-nano-plate catalyst was synthesized by a simple template-free hydrothermal method and applied in the base-catalyzed transesterification of Camelina oil for biodiesel synthesis. The Zn/MgO catalyst calcinated at 873 K exhibited the highest catalytic activity with a yield of 88.7%. This catalytic reaction was performed using 3% w/w of the catalyst with a methanol-to-oil molar ratio of 24:1 at 393 K in 8 h. The excellent catalytic performance is possibly attributed to its favorable textural features with relatively high surface area (69.1 m² g⁻¹) and appropriate size of the mesopores (10.4 nm). In addition, the as-synthesized catalyst demonstrated a greater basic sites density than single mesoporous MgO, which might have been promoted by the addition of Zn, leading to a synergetic interaction that enhanced its catalytic activity. This catalytic system demonstrated high stability for five catalytic runs and catalytic activity with over 84% yield.