Single‐atom catalysts are promising platforms for heterogeneous catalysis, especially for clean energy conversion, storage, and utilization. Although great efforts have been made to examine the bonding and oxidation state of single‐atom catalysts before and/or after catalytic reactions, when information about dynamic evolution is not sufficient, the underlying mechanisms are often overlooked. Herein, we report the direct observation of the charge transfer and bond evolution of a single‐atom Pt/C3N4 catalyst in photocatalytic water splitting by synchronous illumination X‐ray photoelectron spectroscopy. Specifically, under light excitation, we observed Pt−N bond cleavage to form a Pt0 species and the corresponding C=N bond reconstruction; these features could not be detected on the metallic platinum‐decorated C3N4 catalyst. As expected, H2 production activity (14.7 mmol h−1 g−1) was enhanced significantly with the single‐atom Pt/C3N4 catalyst as compared to metallic Pt‐C3N4 (0.74 mmol h−1 g−1).

No abstract

No abstract

We report a novel method for the fabrication of one-component self-folding polymer films. The approach is based on films with a vertical gradient of porosity and was demonstrated on an example of porous polyimide films. The inhomogeneous porosity of the films was achieved through the implementation of capillary forces and gravity during the drying of a dispersion of colloidal particles in a solution of polymer precursor. As a result, three-layered films were formed. A monolayer of particles comprises the top layer, the second layer is the pure polymer, and the third layer is formed by a mixture of particles and polymer. Etching out the particles leaves polyimide film with inhomogeneous distributed pores. These porous polymer films roll and form tubes in organic solvents as well as their vapors and reversibly unfold in air. The obtained films were used for design of actuators, which are able to capture and release different objects through the reversible folding.