Fabrication of Bi2MoO6 Nanosheets/TiO2 Nanorod Arrays Heterostructures for Enhanced Photocatalytic Performance under Visible-Light Irradiation

Pd Nanoparticle-Decorated Novel Ternary Bi2O2CO3-Bi2MoO6-CuO Heterojunction for Enhanced Photo-electrocatalytic Ethanol Oxidation

Recently, photo-electrooxidation of fuel using a noble metal-semiconductor junction has been one of the most promising approaches in fuel cell systems. Herein, we report the development of a Pd-supported Bi2MoO6-Bi2O2CO3-CuO novel ternary heterojunction for ethanol oxidation in alkali in the presence and absence of visible light. Various spectroscopic and microscopic characterization techniques confirm strong coupling between palladium nanoparticles and Bi2MoO6-Bi2O2CO3-CuO ternary heterojunction supports. The photo-electrocatalytic efficacy of the synthesized catalysts was inspected by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The CV study reveals that the forward peak current density (in mA mg-1 of Pd) of the synthesized quaternary heterojunction was about 1482.5, which is 2.4, 4, and 4.6 times higher than that of Pd/CuO (608.3), Pd/Bi2MoO6-Bi2O2CO3 (368.3), and similarly synthesized Pd catalyst (321.5) under visible light radiation. The best heterojunction catalyst shows 2.21-fold higher peak current density in visible light compared to that in dark. CA study reveals that after operation for 6000 s, the current density of the quaternary electrode is 1.5 and 3.4 times greater than that of Pd/CuO and Pd/C catalysts, respectively. The greater photocurrent response, lower photoluminescence (PL) emission intensity, and smaller semicircle arc in the Nyquist plot of the quaternary catalyst demonstrate the efficient segregation and higher charge transfer conductance of photogenerated charges to facilitate the photo-electrooxidation process of ethanol. The stability test shows that the quaternary catalyst loses only 9.8 and 7.7% of its maximum current density after 500 cycles of CV operation in the dark and light, respectively, indicating that light energy is more beneficial in establishing high stability. The dramatic enhancement of the photo-electrocatalytic activity of the quaternary electrode is owing to the lower band gap, high ECSA, enhanced charge separation of photogenerated carriers (e--h+), and all cocatalytic support of Bi2MoO6, Bi2O2CO3, and CuO in Pd/ Bi2MoO6-Bi2O2CO3-CuO under visible light radiation. The morphology and structure of the used quaternary catalyst are tested using FESEM and PXRD. Finally, ex situ FTIR spectroscopy and HPLC techniques help understand the ethanol electrooxidation reaction mechanism.

BiOI/Bi2MoO6 p-n Junction to Enhance Visible Light Photocatalytic Activity toward Environmental Remediation

Photocatalytic degradation of organic pollutants via semiconductors with high visible light response and effective carrier separation is an economical and green route to greatly achieve environmental remediation. Herein, an efficient BiOI/Bi₂MoO₆ p-n heterojunction was in situ fabricated through hydrothermal method by substituting Mo₇O₂₄^6- species for I ions. The characteristic p-n heterojunction exhibited a strongly enhanced visible light responsive absorption from 500 to 700 nm owing to the narrow band gap of BiOI and a greatly effective separation of photoexcited carriers because of the built-in electric field on the interface between BiOI and Bi₂MoO₆. Moreover, the flower-like microstructure also promoted the adsorption of organic pollutants owing to the large surface area (about 10.36 m²/g), good for further photocatalytic degradation. As a result, BiOI/Bi₂MoO₆ p-n heterojunction showed an excellent photocatalytic activity of RhB of almost 95% in a short time of 90 min under wavelength longer than 420 nm, 2.3 and 2.7 times higher compared with single BiOI and Bi₂MoO₆, respectively. This work offers a promising approach to purify the environment through the utilization of solar energy by constructing efficient p-n junction photocatalysts.