Co–Pd/BiVO4: High-performance photocatalysts for the degradation of phenol under visible light irradiation

• Published in: Applied catalysis. B, Environmental Environmental, 2018-05, Vol.224, p.350-359
• Main Authors: Zhang, Kunfeng, Liu, Yuxi, Deng, Jiguang, Xie, Shaohua, Zhao, Xingtian, Yang, Jun, Han, Zhuo, Dai, Hongxing
• Format: Article
• Language: English
• Subjects: Co–Pd bimetallic nanoparticle; Leaf-like bismuth vanadate; Photocatalytic degradation mechanism; Photocatalytic phenol degradation; Supported noble metal photocatalyst
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2017.10.044

0.062Co1.7Pd/BiVO4 exhibits excellent photocatalytic performance for phenol degradation, which is attributable to the formation of highly active superoxide anion radicals on the CoxPd surface and photoinduced holes in BiVO4. [Display omitted] •Bimetallic CoxPd nanoparticles are synthesized via the PVA-protected reduction route.•CoxPd loading enhances charge carrier separation and phenol degradation.•0.062Co1.70Pd/BiVO4 possesses the highest Oads and Pd0 concentrations.•0.062Co1.70Pd/BiVO4 displays the strongest photocurrent response.•Superoxide anion radicals and photoinduced holes govern the photocatalytic activity. Leaf-like monoclinic BiVO4 and yCoxPd/BiVO4 (CoxPd loading (y)=0.060−0.092wt%; Co/Pd molar ratio (x)=0.26−1.70) photocatalysts were prepared using the hydrothermal and polyvinyl alcohol-protected reduction methods, respectively. The Co−Pd nanoparticles (NPs) with a size of 4–6nm were well dispersed on the surface of leaf-like BiVO4. The bimetallic Co−Pd-loaded BiVO4 samples performed much better than the monometallic Co- or Pd-loaded counterpart, with the 0.062Co1.70Pd/BiVO4 sample showing the best photocatalytic performance (the time for 90% phenol removal was 3h under visible light irradiation) and good photocatalytic stability. The pseudo-first-order reaction rate constants (0.4753−0.8367h−1) obtained over yCoxPd/BiVO4 were much higher than those (0.0619−0.3788h−1) obtained over BiVO4, 0.058Co/BiVO4, and 0.083Pd/BiVO4, with the 0.062Co1.70Pd/BiVO4 sample possessing the highest rate constant. In-depth investigations of X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and photoelectrochemical measurements reveal that high dispersion of bimetallic Co–Pd NPs increased the surface Pd0 and superoxide anion radical concentrations and suppressed the recombination of photoinduced electrons and holes (hence enhancing the photocatalytic activity of yCoxPd/BiVO4). The partial deactivation of the 0.062Co1.70Pd/BiVO4 sample after 15h of three recycle tests was mainly due to the decrease in adsorbed oxygen species concentration. In addition, the possible photocatalytic phenol degradation mechanism over the 0.062Co1.70Pd/BiVO4 sample was also proposed. We believe that the BiVO4-supported Co–Pd NPs have promising applications for the photocatalytic elimination of organic pollutants in wastewater.