Benign role of Bi on an electrodeposited CuO semiconductor towards photo-assisted H generation from water

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2016-06, Vol.4 (23), p.9244-9252
• Main Authors: Shyamal, Sanjib, Hajra, Paramita, Mandal, Harahari, Bera, Aparajita, Sariket, Debasis, Satpati, Ashis Kumar, Kundu, Sukumar, Bhattacharya, Chinmoy
• Format: Article
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c6ta03237k

In this paper we report a Bi modified Cu 2 O semiconductor (SC) for improved photoelectrochemical (PEC) hydrogen (H 2 ) production from aqueous solution. For the first time, we found out that the PEC performance of SC thin films improve dramatically by ∼2 fold when Bi nanoparticles (BiNPs) are added in the form of a suspension or act as a matrix coated over ITO glass during electrodeposition of Cu 2 O. On the other hand, the addition of an optimized amount of Bi 3+ ions (10 nM) in the deposition bath also facilitated the hydrogen evolution reaction over Cu 2 O. Maximum photocurrents for the Cu 2 O film developed from these three different conditions are: −5.2 mA cm −2 for ITO/BiNP film /Cu 2 O, −4.9 mA cm −2 for ITO/BiNP sus /Cu 2 O, and −3.7 mA cm −2 for ITO/Bi ion /Cu 2 O, whereas that for pure Cu 2 O on ITO appears as −2.6 mA cm −2 . This is the highest reported photocurrent of Cu 2 O on any conducting glass substrates without employing any hydrogen evolution catalyst. SEM and XRD studies of the films indicate that the materials are composed of "cubic" crystallites of preferential (111) orientation, and their size varies from 18-26 nm. Addition of Bi modifies the band position with a decrease in the bandgap energy of Cu 2 O. Smaller charge-transfer resistance ( R ct ) and ohmic resistance ( R s ) facilitate the H 2 evolution reaction over the ITO/BiNP film /Cu 2 O film, whereas its lowest carrier density suggests minimum defect sites, i.e. better crystallinity of the film matrix. Bi-modified Cu 2 O possesses a superior photocatalytic water reduction due to its surface morphology, smaller crystallinity, lower charge transfer resistance, and fewer defect sites.