Enhanced optical properties of BiVO4 photoanode with subwavelength moth-eye structure fabricated via e-beam evaporation and direct printing

초록

Photoelectrochemical (PEC) water splitting which harnesses solar radiation (an infinite energy source) for clean hydrogen production without carbon-dioxide emissions is an ideal eco-friendly energy technology. The core reactions in PEC water splitting involving the oxidation and reduction of water are driven by electron–hole pairs generated through solar energy absorption. Consequently the light-absorption efficiency emerges as a critical parameter in PEC devices. Conventional thin-film-type photoanodes however grapple with limited absorption due to their high reflectance hindering absorption and carrier separation efficiency. Conversely moth-eye-structured photoanodes exhibit an anti-reflection effect stemming from their subwavelength structure markedly enhancing light-absorption efficiency. In this study we present the design and fabrication of a densely packed moth-eye-structured bismuth vanadate (BiVO4) (M-BVO) photoanode which is engineered to possess superior light absorption properties. The photoanode was fabricated via direct printing electron-beam evaporation and Vanadium calcination processes. The light absorption of the resulting M-BVO photoanode increased to approximately 92 % within the 300–500 nm wavelength range with the absorption efficiency (ηabs) surging to 82.9 %. This represents a 23.5 % enhancement compared to its flat BiVO4 counterparts. Impressively the photocurrent density of M-BVO reached 2.98 mA cm−2 at 1.23 VRHE 37.6 % higher than that of flat BiVO4. These results indicate that the PEC efficiency can be significantly increased through moth-eye structuring emphasizing the indispensable role of nanostructure research in the manufacture of high-efficiency photoanodes. © 2024 Elsevier B.V.

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