Tailoring Interfaces for Electrochemical Synthesis of Semiconductor Films: BiVO₄, Bi₂O₃, or Composites

Abstract

The mechanistic aspects of a two-step method for the electrodeposition of a BiVO4 semiconductor (previously developed in the Rajeshwar/Tacconi laboratory) were elaborated by the combined application of voltammetry and EQCM. The electrosynthesized films were also characterized ex situ using SEM, EDX, XRD, and XPS. Stripping of pre-electrodeposited bismuth films, followed by reaction either with VO4 3− (formed by hydrolysis from the initially added VO3 − species) or with hydroxide ions, produced BiVO4 or Bi2O3 thin films in situ on the Pt electrode. The deposition potential, pH of the electrolyte, and choice of vanadium precursor were shown to be crucial variables in the composition of the electrodeposited film. When a more positive potential than 0.5 V (vs Ag/AgCl reference) was applied to the Bi-modified electrode in VO3 −-containing electrolyte, the content of Bi2O3 in the film increased instead of BiVO4. Stripping efficiency of the predeposited bismuth layer was increased at acidic electrolytes and resulted in higher BiVO4 content in electrodeposited films, whereas hydrolytic conversion of VO3 − to VO4 3− was promoted in basic electrolytes. Formation of Bi2O3 was also favored by the use of alkaline electrolytes (e.g., pH 10) for the electrodeposition. Photoelectrochemical experiments showed the electrosynthesized BiVO4 to be an n-type semiconductor, and reproducible photocurrents were obtained using a Na2SO4 supporting electrolyte.

Promoting role of bismuth on carbon nanotube supported platinum catalysts in aqueous phase aerobic oxidation of benzyl alcohol

“…One pair of the strongest peeks at 159.2 and 164.5 eV is assigned to Bi 2 O 3 , and accounts for 84.1% of the total Bi amount; another weaker pair of peaks at 157.6 and 162.5 eV is assigned to Bi metal [49,50], and accounts for 10.2%; the other pair of peaks at 161.0 and 166.7 eV is assigned to Bi oxides with higher value status than Bi 2 O 3 , denoted as Bi 2 O 3+x in Table 1b, Similar results were also reported by other researchers [9,53]. Alternatively, a pair of overlapping peaks appear at the range from -0.5 to 0.1 V of PtBi/CNT curves, which are attributed to the oxidation of Pt and Bi species.…”

“…Compared to Pt/CNT, its binding energies and the content of PtO have negligible changes, indicating that Pt valence status has slight difference between Pt/CNT and PtBi/CNT. The Bi 4f spectrum for Bi/CNT can be described by a pair of peaks at 159.4 eV (Bi 4f 7/2 ) and 164.7 eV (Bi 4f 5/2 ), which are typical characteristic peaks of Bi 2 O 3 [49,50]. While for PtBi/CNT, the Bi 4f 7/2 and Bi 4f 5/2 signals with much larger peak width than that of Bi/CNT, should be described by 3 pairs of peaks.…”

“…The Bi 4f spectrum for Bi/CNT can be described by a pair of peaks at 159.4 eV (Bi 4f 7/2 ) and 164.7 eV (Bi 4f 5/2 ), which are typical characteristic peaks of Bi 2 O 3 [49,50]. While for PtBi/CNT, the Bi 4f 7/2 and Bi 4f 5/2 signals with much larger peak width than that of Bi/CNT, should be described by 3 pairs of peaks.One pair of the strongest peeks at 159.2 and 164.5 eV is assigned to Bi 2 O 3 , and accounts for 84.1% of the total Bi amount; another weaker pair of peaks at 157.6 and 162.5 eV is assigned to Bi metal [49,50], and accounts for 10.2%; the other pair of peaks at 161.0 and 166.7 eV is assigned to Bi oxides with higher value status than Bi 2 O 3 , denoted as Bi 2 O 3+x in Table 1b, and which accounts for 3.7%. To summarize these XPS results, the main existing status of Pt component in both of Pt/CNT and PtBi/CNT is Pt 0 ; and almost all of Bi component in Bi/CNT is Bi 2 O 3 ; and dissimilarly, most Bi component in PtBi/CNT is Bi 2 O 3 excepting 10.4% of Bi 0 and 3.7% Bi 2 O 3+x species.…”

New application for the BiVO4 photoanode: A photoelectroanalytical sensor for nitrite

“…This material shows as main advantages its nontoxicity, and chemical and electrochemical stability in aqueous solutions. It is also inexpensive, presenting a high photoelectrochemical activity, and a small band-gap (~2.4 eV -monoclinic structure), which makes it suitable to be excited by visible light irradiation [14,15]. A recent study for hydrogen production allied with oxidation of hydrazine demonstrated photocurrent response at Mo doped BiVO 4 electrode dependent of hydrazine concentration.…”

Photoanodes on titanium substrates: one-step deposited BiVO4 versus two-step nano-V2O5 films impregnated with Bi3+

“…More recent studies have focused on the preparation of BiVO4, seeking to improve photocatalytic activity by using various strategies such as morphology control, construction of nano-composite structures, and doping. BiVO4 can be fabricated by solution-based methods including aqueous, hydrothermal, and solvothermal processes [7][8][9] or by spray pyrolysis [10]. In most of the synthesis methods proposed in the literature, several hours of reflux and use of aggressive chemicals such as concentrated nitric acid are required.…”