Influence of Conditions of Microreactor Mixing of Reagent Solutions on the Formation and Photocatalytic Properties of BiVO₄

Microreactor synthesis of bismuth vanadate is carried out with variations in the solution flow rates and reagent concentrations in the solutions. With an increase in the concentration of reagents from 0.01 to 0.03 mol/L (at solution flow rates of 1.5 L/min), an increase in the crystallite size is observed from ~37 to ~76 nm. With an increase in flow rates from 1.5 to 3.2 L/min, the crystallite size and the proportions of monoclinic and tetragonal phases of bismuth vanadate for concentrations of 0.01 and 0.02 mol/L differ insignificantly (within the error limits). This means that a flow rate of 1.5 L/min is sufficient to ensure the required micro-mixing quality. An increase in the flow rate of the reagents during microreactor mixing leads to an increase in the rate of photocatalytic decomposition of the dye. For the same flow rate, the best photocatalytic characteristics are demonstrated by samples obtained with a lower concentration of the initial reagents, which provides a larger proportion of the monoclinic phase of BiVO₄ and a smaller crystallite size of this phase. The possibility of controlled microreactor synthesis of bismuth vanadate with a given phase composition, morphology, and crystallite sizes is shown.