Boosting the visible-light photoactivities of BiVO4 nanoplates by Eu doping and coupling CeOx nanoparticles for CO2 reduction and organic oxidation

Abstract

Comprehensively extending the visible light response, enhancing charge separation and promoting surface catalysis of rationally designed photocatalysts are highly desired for improving visible-light activity. For this, CeO_x coupled Eu³⁺ doped BiVO₄ nanoplates (NPs) have been prepared by first synthesizing Eu³⁺ doped BiVO₄ nanoplates via a hydrothermal route and then coupling CeO_x nanoparticles through a wet-chemical method. In contrast to the photocatalytic and photo-degradative performance of BiVO₄, it is observed that the amount-optimized CeO_x/BiVO₄:Eu³⁺ nanoparticles possess ∼3-time enhancement in visible-light photocatalytic performance for CO₂ conversion to CH₄ and degradation of 2,4-dichlorophenol (2,4-DCP). According to the results obtained from XPS, produced ˙OH amount measurements, surface photovoltage response (SPS) and transient photoluminescence spectroscopy (PL), the promoted visible-light photoactivities of CeO_x/BiVO₄:Eu³⁺ NPs are caused by the combination of the extended visible-light absorption by Eu³⁺ doping and enhanced charge separation by coupling CeO_x and absorbing excited high level photoelectrons from BiVO₄. In addition, raising the valence band extends visible light utilization which consequently increases the production of high-level energy electrons. Moreover, it is confirmed from CO₂-TPD and electrochemical CO₂ reduction that the high photoactivities are also ascribed to the enhanced surface adsorption of CO₂ and catalytic ability of coupled CeO_x.