The Co–Pi cocatalyst improves the PEC performance of a hematite film by accelerating the H2O oxidation kinetics and suppressing the charge recombinations.

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The water oxidation efficiency of hematite photoanodes is mainly limited by low visible light absorption and short hole diffusion length. Herein, we report on production of nanoporous columnar hematite films modified with Au nanoparticles (NPs) to overcome these drawbacks. The hematite films are prepared by electron beam evaporation. By optimization of deposition conditions including film thickness, annealing and performing the evaporation under oblique angle, an efficient photoelectrochemical (PEC) performance is achieved from the pristine hematite photoanode. Then, Au NPs are infiltrated into the hematite films by a spin coating process. The water oxidation of hematite films is further enhanced after Au modification. The most efficient electrode generates a photocurrent density of 2.7 mA cm−2 at 1.5 V (RHE), showing about two‐fold improvement relative to that of bare hematite. Optical and electrochemical analyses suggest that the improvement after Au modification can be attributed to plasmonic and facilitating surface charge transfer. The contributions of different plasmonic mechanisms to the photocurrent enhancement are qualitatively discussed based on optical characterization and electromagnetic simulations. Electrochemical impedance spectroscopy is carried out to confirm the improvement of surface charge transport by the Au NPs. Our findings show that Au modification is a favorable strategy to improve the PEC performance of hematite photoanodes prepared by PVD methods.

In this paper, a plasmonic refractive index sensor using a D-shaped optical fiber coated by tantalum has been proposed. The interaction between fiber fundamental mode and plasmonic mode which lead to the formation of resonance peaks depending on the analyte refractive index (RI) are investigated in detail. Using spectral sensitivity methods, the sensing performance of the proposed sensor for detecting analytes is numerically studied. The effect of various design parameters of proposed sensor are optimized numerically to achieve the maximum wavelength sensitivity. The proposed D-shaped optical fiber sensor has a RI detection range of 1.30 to 1.43 and exhibits a non-linear increasing spectral sensitivity from 1300 nm/RIU to 3900 nm/RIU. The proposed RI sensor is attractive for detecting different RI chemical and biochemical samples due to simple design, relatively large detection range, cost-effective, non-toxic nature and highly corrosion resistivity plasmonic material.

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