Improved photoelectrocatalytic activities of BiOCl with high stability for water oxidation and MO degradation by coupling RGO and modifying phosphate groups to prolong carrier lifetime

- Phosphate modified RGO/BOC nanocomposite photoanodes have been prepared.
- Nanocomposite photoanode with high stability exhibits improved photoelectrocatalytic activities.
- Produced hydroxyl radical amounts are agreeable with improved photoelectro- catalytic activities.
- Improved photoactivities are attributed to enhanced charge separation via controlling electrons and holes.
- High stability results from the substitution of Cl with phosphate groups to inhibit forming Cl-vacancy.

For an efficient photoelectrocatalysis on bismuth oxychloride (BiOCl), it is highly desired to enhance the photogenerated charge separation and the photochemical stability. Herein, photoelectrocatalytic activities of BiOCl photoanodes for water oxidation to evolve O2 and for methyl orange (MO) degradation have been greatly improved through firstly coupling with reduced graphene oxide (RGO) and then modifying with phosphoric acid. It is shown that the optimal amount of phosphate modified RGO/BiOCl nanocomposite photoanode exhibits 3.8-time and 8.4-time activity enhancement respectively for water oxidation and MO degradation, compared to the bare BiOCl. It is confirmed that the improved activities are attributed to enhanced charge separation and prolonged carrier lifetime of BiOCl after chemically coupling with RGO to collect electrons and modifying with phosphate groups to trap positive holes via the formed negative field on the surfaces, mainly based on electrochemical impedance spectra, time-resolved surface photovoltage responses, and produced hydroxyl radical amounts. Moreover, it is concluded that the phosphate groups are modified on BiOCl by replacing photochemically-unstable chloride ions, consequently leading to the enhanced stability. Expectedly, this positive strategy is also applicable to the visible-response BiOBr as an efficient photoanode. This work opens up a feasible route to efficiently improve the PEC performance of BiOX-based nanomaterials with high stability.

166Improved photoelectrocatalytic activity of BiOCl with high stability results from enhanced charge separation by coupling RGO and modifying phosphate groups.