We propose a novel and simple method for generating optical vortex with high topological charge (TC), merely using an asymmetrical pinhole plate illuminated by plane wave. N pinholes are arranged along a particular spiral line around the plate origin, with constant azimuth angle increment and varied radial distances. The radial differences introduce a constant variation of m/N wavelength to the optical paths from the N pinholes to the observation plane origin, and this increases the phases of the transmitting waves by progressively 2mπ/Nand totally 2mπ. We numerically calculate the transmitted light field according to the Fresnel diffraction theory, and find the vortex with TC m around the observation plane origin. The experimental verifications are performed using some self-made asymmetrical pinhole plates fabricated by a femtosecond laser, with the high TC vortices both generated and detected in a Mach-Zehnder type interferometer. The experimental results coincide with the theoretical simulations well.
Electrochemical CO 2 reduction (ECR) technology is promising to produce value-added chemicals and alleviate the climate deterioration. Interface engineering is demonstrated to improve the ECR performance for metal and oxide composite catalysts. However, the approach to form a substantial interface is still limited. In this work, we report a facile one-pot coprecipitation method to synthetize novel silver and silver-doped ceria (Ag/CeO 2 ) nanocomposites. This catalyst provides a rich 3D interface and high Ce 3+ concentration (33.6%), both of which are beneficial for ECR to CO. As a result, Ag/CeO 2 exhibits a 99% faradaic efficiency and 10.5 A g −1 mass activity to convert CO 2 into CO at an overpotential of 0.83 V. The strong interfacial interaction between Ag and CeO 2 may enable the presence of surface Ce 3+ and guarantee the improved durability during the electrolysis. We also develop numerical simulation to understand the local pH effect on the ECR performance and propose that the superior ECR performance of Ag/CeO 2 is mainly due to the accelerated CO formation rate rather than the suppressed hydrogen evolution reaction.
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