Boosted Z-scheme photocatalytic overall water splitting with faceted Bi4TaO8Cl crystals as water oxidation photocatalyst

We have identified a facet-assisted mechanism for photocarrier separation in flux-treated Bi4TaO8Cl crystals that expose mainly {001} and {110} facets. These two crystal facets have different energy states that provide an internal electric field to split photocarriers towards different crystal facets. We have further leveraged the phenomenon by facet-selective deposition of CoOx cocatalyst at {001} crystal facets where holes are accumulated to expedite interfacial charge transfer reactions. The coupling of these two facet-engineering techniques brings exquisite control over the flow of photocarriers which cascade continuously from bulk to the surface for catalytic reactions. Under optimal conditions, the CoOx-deposited Bi4TaO8Cl achieves an unprecedentedly high apparent quantum efficiency of 27% at 420 & PLUSMN; 20 nm for water oxidation into O2. Stable overall water splitting into H2 and O2 (molar ratio 2:1) under visible light irradiation has also been realized in a Z-scheme system employing the CoOx-deposited Bi4TaO8Cl as the O2-evolution moiety.

Automated summary

We have discovered a facet-assisted mechanism for separating photocarriers in flux-treated Bi4TaO8Cl crystals with {001} and {110} facets. These facets have different energy states that generate an internal electric field to direct photocarriers to different facets. By selectively depositing CoOx cocatalyst on the {001} facets, we enhance interfacial charge transfer reactions. This facet engineering enables controlled flow of photocarriers from the bulk to the surface for catalytic reactions, achieving unprecedented high quantum efficiency and stable water splitting.