Carbon quantum dots as a visible light sensitizer to significantly increase the solar water splitting performance of bismuth vanadate photoanodes

Here, we demonstrate that carbon quantum dots (CQDs), as a low cost, chemically stable, and environmentally friendly photosensitizer, can dramatically broaden the light absorption range to the entire visible range. Consequently, the NiOOH/FeOOH/CQD/BiVO₄ (NFCB) photoanode has achieved a remarkable photocurrent density of 5.99 mA cm^-2 at 1.23 V vs. RHE under AM 1.5G in KH₂PO₄ aqueous solution without a hole scavenger (pH = 7) and a record high applied bias photon-to-current efficiency of 2.29% at 0.6 V vs. RHE for BiVO₄-based photoanodes. This novel NFCB photoanode could operate stably for 10 h with a Faraday efficiency of ∼95%, demonstrating the great potential of using CQDs for solar water splitting.