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 NiFeO_x 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.

金属氧化物由于其坚固性和低成本而在光电化学（PEC）水分解方面很有前景。然而，不良的电荷载流子传输阻碍了它们的活性，特别是在低偏置电压下。在这里，我们展示了将磷掺杂到钒酸铋 (BiVO ₄ ) 光电阳极中对于高效低偏置 PEC 水分解的非凡功效。所得BiVO ₄光电阳极在电势低至0.6和1.0 V _RHE时分别显示出80%和99%的分离效率。理论模拟和实验分析共同验证了记录性能源自独特的磷掺杂BiVO ₄结构，同时介导载流子密度、陷阱态和小极化子跳跃。使用 NiFeO _x助催化剂，BiVO ₄光电阳极在 0.6 V _RHE下实现了 2.21% 的施加偏置光子电流效率。对 BiVO ₄性能增强的机理理解为大多数光活性金属氧化物的陷阱态钝化和极化子跳跃提供了关键见解。