Design and fabrication of BiV(O, N)4 p-n homojunction solid solutions for enhanced methylene blue degradation via LED light irradiation

[Display omitted] •Route to form BiVO4 p-n homojunction by controlling the N doping level is presented.•BiVO4 p-n homojunction is designed from first principles quantum mechanics.•BiVO4 is fabricated subsequently using unintentional doping in a single pot.•BiVO4 is able to degrade 88% MB dye in just 20 minutes under LED light.•MB dye degradation of BiVO4 homojunction out-performs that of the heterojunction.•BiVO4 p-n heterojunction enables larger photoelectron/photohole populations. Quantum efficiency of photoelectrons and photoholes depends on both their populations and ability to stay separated before reaching the targeted reaction sites. Hence, we present a design and practice of a new strategy to form BiVO4 p-n homojunctions by simply controlling the nitrogen doping levels. This is the first time a BiVO4 p-n homojunction is (1) designed from first principles quantum mechanics, (2) fabricated subsequently using unintentional doping in a single pot, and (3) able to degrade 88% methylene blue dye (MB) in just 20 mins under LED light irradiation. To the best of our knowledge, this study reports the fastest degradation rate of methylene blue dyes using BiVO4. We also compared the results of our p-n homojunction (un-intentionally doped or U-N-doped) with that of a heterojunction (intentionally-doped or I-N-doped Bi2O3/BiVO4) with regards to the photocatalytic performance in MB dye degradation. As expected the p-n homojunction out-performs that of the p-n heterojunction, although the heterojunction enables larger photoelectron/photohole populations than that of homojunction. Further, we propose that the formation of BiVO4 p-n homojunctions was the origin of the recent breakthrough in water splitting research recently reported by Kim et al. (2014). This design strategy and the simple one-pot synthesis technique have immediate implications to solar energy applications beyond dye degradation and water-splitting.