Nanoporous BiVO<sub>4</sub> Decorated with Carbon Quantum Dots for Efficient Photoelectrochemical Water Splitting
Bo Peng, Xiaoxuan Zhao, Chunmei Li, Duo Zhang, Nan Zhou, Yuting Zhou, Shoubing Ding, Zhimin Wu, Yuli Xiong
Abstract
The sluggish kinetics of oxygen evolution is widely recognized as one of the major challenges in developing a BiVO 4 -based photoanode. To address this intrinsic limitation, we present an integrated photoanode composed of nanoporous BiVO 4 decorated with 5 nm carbon quantum dots (CQDs). The CQDs function as an efficient hole transfer layer due to their lower surface potential, creating an outward interfacial built-in electric field with the higher surface potential of bulk BiVO 4 . This electric field is capable of driving photogenerated holes to the CQDs’ surface for efficient water oxidation. The CQDs-BiVO 4 demonstrates an improved photocurrent of 2.7 mA cm –2 at 1.23 V vs RHE under simulated sunlight, which is approximately 3.0 times higher than that of pristine BiVO 4 . The nanoporous CQDs-BiVO 4 also achieves an enhanced surface charge transfer efficiency of 45.8% and a shorter electron transport time of 0.23 ms at a flow rate of 300 W m –2 . Time-resolved photoluminescence analysis reveals that a longer lifetime is achieved (τ 1 = 3.7 ns and τ 2 = 49.0 ns) for CQDs-BiVO 4, confirming that the reduced electron–hole recombination is beneficial for bulk charge transfer.