Ru-regulated electronic structure CoNi-MOF nanosheets advance water electrolysis kinetics in alkaline and seawater media.

Herein, an ion-exchange strategy is utilized to greatly improve the kinetics of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by Ru-modified CoNi- 1,3,5-Benzenetricarboxylic acid (BTC)-metal organic framework nanosheets (Ru@CoNi-MOF). Due to the higher Ni active sites and lower electron transfer impedance, Ru@CoNi-MOF catalyst requires the overpotential as low as 47 and 279 mV, at a current density of 10 mA/cm2 toward HER and OER, respectively. Significantly, the mass activity of Ru@CoNi-MOF for HER and OER are 25.9 and 10.6 mA mg-1, nearly 15.2 and 8.8 times higher than that of Ni-MOF. In addition, the electrolyzer of Ru@CoNi-MOF demonstrates exceptional electrolytic performance in both KOH and seawater environment, surpasses the commercial Pt/C||IrO2 couple. Theoretical calculations prove that introducing Ru atoms in - CoNi-MOF modulates the electronic structure of Ni, optimizes adsorption energy for H* and reduces energy barrier of metal organic frameworks (MOFs). This modification significantly improves the kinetic rate of the Ru@CoNi-MOF during water splitting. Certainly, this study highlights the utilization of MOF nanosheets as advanced HER/OER electrocatalysts with immense potential, and will paves a way to develop more efficient MOFs for catalytic applications.

Chelated Ion-Exchange Strategy toward BiOCl Mesoporous Single-Crystalline Nanosheets for Boosting Photocatalytic Selective Aromatic Alcohols Oxidation.

The photoresponse and photocatalytic efficiency of bismuth oxychloride (BiOCl) are greatly limited by rapid recombination of photogenerated carriers. The construction of porous single-crystal BiOCl photocatalyst can effectively alleviate this issue and provide accessible active sites. Herein, a facile chelated ion-exchange strategy is developed to synthesize BiOCl mesoporous single-crystalline nanosheets (BiOCl MSCN) using acetic acid and ammonia solution respectively as chelating agent and ionization promoter. The strong chelation between acetate ions and Bi3+ ions introduces acetate ions into the precipitated product to exchange with Cl- ions, resulting in large lattice mismatch, strain release, and formation of void-like mesopores. The prepared BiOCl MSCN photocatalyst exhibits excellent catalytic performance with 99% conversion and 98% selectivity for oxidation of benzyl alcohol to benzaldehyde and superior general adaptability for various aromatic alcohols. The theoretical calculations and characterizations confirm that the superior performance is mainly attributed to the abundant oxygen vacancies, plenty of accessible adsorption/active sites and fast charge transport path without grain boundaries.

Ion-Exchange Strategy for Metal-Organic Frameworks-Derived Composites with Tunable Hollow Porous and Microwave Absorption.

Hollow metal-organic frameworks (MOFs) with careful phase engineering have been considered to be suitable candidates for high-performance microwave absorbents. However, there has been a lack of direct methods tailored to MOFs in this area. Here, a facile and safe Ni2+ -exchange strategy is proposed to synthesize graphite/CoNi alloy hollow porous composites from Ni2+ concentration-dependent etching of Zeolite imidazole frame-67 (ZIF-67) MOF and subsequent thermal field regulation. Such a special combination of hollow structure and carefully selected hybrid phase are with optimized impedance matching and electromagnetic attenuation. Especially, the suitable carrier transport model and the rich polarization site enhance the dielectric loss, while more significant hysteresis loss and more natural resonance increase the magnetic loss. As a result, excellent microwave absorbing (MA) performances of both broadband absorption (7.63 GHz) and high-efficiency loss (-63.79 dB) are obtained. Moreover, the applicability and practicability of the strategy are demonstrated. This work illustrates the unique advantages of ion-exchange strategy in structure design, component optimization, and electromagnetic regulation, providing a new reference for the 5G cause and MA field.

Structural Engineering of Hollow Microflower-like CuS@C Hybrids as Versatile Electrochemical Sensing Platform for Highly Sensitive Hydrogen Peroxide and Hydrazine Detection.

Designing metal sulfides with unique configurations and exploring their electrochemical activities for hydrogen peroxide (H2O2) and hydrazine (N2H4) is challenging and desirable for various fields. Herein, hollow microflower-like CuS@C hybrids were successfully assembled and further exploited as a versatile electrochemical sensing platform for H2O2 reduction and N2H4 oxidation, of which the elaborate strategies make the perfect formation of hollow architecture, providing considerable electrocatalytic sites and fast charge transfer rate, while the appropriate introduction polydopamine-derived carbon skeleton facilitates the electronic conductivity and boosts structural robustness, thus generating wide linear range (0.05-14 and 0.01-10 mM), low detection limit (0.22 µM and 0.07 µM), and a rather low overpotential (-0.15 and -0.05 V) toward H2O2 and N2H4, as well as good selectivity, excellent reproducibility, and admirable long-term stability. It should be highlighted that the operating potentials can compare favorably with those of some reported H2O2 and N2H4 sensors based on noble metals. In addition, good recoveries and acceptable relative standard deviations (RSDs) attained in serum and water samples fully verify the accuracy and anti-interference capability of our proposed sensor systems. These results not only elucidate an effective structural nanoengineering strategy for electroanalytical science but also advance the rational utilization of H2O2 and N2H4 in practicability.