We report on the synthesis of iron-nickel sulfide (INS) ultrathin nanosheets by topotactic conversion from a hydroxide precursor. The INS nanosheets exhibit excellent activity and stability in strong acidic solutions as a hydrogen evolution reaction (HER) catalyst, lending an attractive alternative to the Pt catalyst. The metallic α-INS nanosheets show an even lower overpotential of 105 mV at 10 mA/cm2 and a smaller Tafel slope of 40 mV/dec. With the help of DFT calculations, the high specific surface area, facile ion transport and charge transfer, abundant electrochemical active sites, suitable H+ adsorption, and H2 formation kinetics and energetics are proposed to contribute to the high activity of the INS ultrathin nanosheets toward HER.

The water-gas shift (WGS) reaction is central to a spectrum of industrially important catalytic processes, ranging from the manufacture of hydrogen to the processing of biomassderived feedstocks. Recently, oxide-supported Au catalysts have attracted attention for lowtemperature WGS reactions, but the role of the Au/oxide interface in promoting this chemistry remains under debate. In this contribution, we combine periodic Density Functional Theory (DFT) calculations, detailed microkinetic modeling, and rigorous kinetic measurements to elucidate the impact of this interface on the molecular-level features of WGS chemistry of a gold nanowire supported on a MgO(100) substrate. The results demonstrate that the barrier to activate water, which is prohibitively high (~2 eV) on a clean Au(111) surface, is decreased to essentially zero at the Au/MgO interface. From the DFTcalculated energetics, a dual-site microkinetic model of the Au/MgO interface is constructed. Rate and thermodynamic control analysis demonstrate both the high degree of kinetic control of COOH formation at the interface and a strong influence of competitive adsorption between CO and H. A procedure to refine the microkinetic predictions by iterative replacement of the energies of kinetically sensitive steps with a higher accuracy hybrid HSE06 prediction is introduced, and the determined effective activation barriers and reaction orders agree well with the results of detailed kinetic measurements on Au nanoparticles on MgO substrates. The results clearly show the critical role that the metal/oxide interface plays in WGS catalysis, and the approach introduced to predict kinetics at the metal/oxide interface should be applicable to a variety of catalytic processes on oxide-supported metal nanoparticles.

No abstract

No abstract

Hybrid perovskite thin films are prone to producing surface vacancies during the film formation, which degrade the stability and photovoltaic performance. Passivation via post‐treatment can heal these defects, but present methods are slightly destructive to the bulk of 3D perovskite due to the solvent effect, which hinders fabrication reproducibility. Herein, nondestructive surface/interface passivation using 4‐fluoroaniline (FAL) is established. FAL is not only an effective antisolvent candidate for surface modification, but also a large dipole molecule (2.84 Debye) with directional field for charge separation. Density functional theory calculation reveals that the nondestructive properties are attributed to both the conjugated amine in aromatic ring and the para‐fluoro‐substituent. A hot vapor assisted colloidal process is employed for the post‐treatment. The molecular passivation yields an ultrathin protection layer with a hydrophobic fluoro‐substituent tail and thus enhances the stability and optoelectronic properties. FAL post‐treated perovskite solar cell (PSC) delivers a 20.48% power conversion efficiency under ambient conditions. Micro‐photoluminescence reveals that passivation activates the dark defective state at the surface and interface, delivering the impact picture of boundary on the local carriers. This work demonstrates a generic nondestructive chemical approach for improving the performance and stability of PSCs.