Low-bias photoelectrochemical water splitting via mediating trap states and small polaron hopping

作者：Wu, Hao; Zhang, Lei; Du, Aijun; Irani, Rowshanak; van de Krol, Roel; Abdi, Fatwa F.; Ng, Yun Hau^*

来源：Nature Communications, 2022, 13(1): 6231.

DOI：10.1038/s41467-022-33905-6

• ELASTIC BAND METHOD
• BIVO4 PHOTOANODES
• TRANSPORT
• PHOTOCATALYST
• CONDUCTIVITY
• PHOTOCURRENT
• TEMPERATURE
• PERFORMANCE
• EFFICIENCY
• OXIDE

Metal oxides are promising for photoelectrochemical (PEC) water splitting due to their robustness and low cost. However, poor charge carrier transport impedes their activity, particularly at low-bias voltage. Here we demonstrate the unusual effectiveness of phosphorus doping into bismuth vanadate (BiVO4) photoanode for efficient low-bias PEC water splitting. The resulting BiVO4 photoanode shows a separation efficiency of 80% and 99% at potentials as low as 0.6 and 1.0 V-RHE, respectively. Theoretical simulation and experimental analysis collectively verify that the record performance originates from the unique phosphorus-doped BiVO4 configuration with concurrently mediated carrier density, trap states, and small polaron hopping. With NiFeOx cocatalyst, the BiVO4 photoanode achieves an applied bias photon-to-current efficiency of 2.21% at 0.6 V-RHE. The mechanistic understanding of the enhancement of BiVO4 properties provides key insights in trap state passivation and polaron hopping for most photoactive metal oxides. @@@ While photoelectrochemical water splitting produces fuel from solar energy, a large fraction of photoanode photoexcited charge carriers cannot be extracted efficiently at low bias voltages. Here, authors improve the charge transport in P-doped BiVO4 by mediating polaron hopping and trap states.

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