Systematic Investigation of BiVO 4 /FeOOH Photoanode via Experimental and Theoretical Approach and Constructing Tandem Photoelectrochemical Cell With CuO/AlO x /RuO 2 Photocathode for Solar Water Splitting

Photoelectrochemical (PEC) water splitting is an effective approach for green hydrogen production. For practical applications, it is essential to use a PEC cell in a two‐electrode configuration at zero bias, which is achieved by utilizing both photoanode and photocathode in a tandem manner, which provides sufficient photovoltage and maximum optical absorption. Here, to construct a PEC tandem device, the BiVO 4 /FeOOH photoanode and CuO/AlO x /RuO 2 photocathode were taken. Here, the BiVO 4 /FeOOH photoanode delivers a higher photocurrent density of ~2.96 mA cm −2 , which is ~2.7‐fold higher than pristine BiVO 4 (1.08 mA cm −2 at +1.23 V RHE ). The theoretical results show that the continuous distribution of DOS in the conduction band after the loading of FeOOH provides evidence for facile electron transfer in BiVO 4 /FeOOH. Besides, the CuO/AlO x /RuO 2 photocathode exhibits a photocurrent density of −2 mA cm −2 at +0.3 V RHE . After constructing the BiVO 4 /FeOOH || CuO/AlO x /RuO 2 tandem device, it produced a photocurrent density of ~0.4 mA cm −2 at zero bias with a photovoltage of ~0.65 V, and at +1 V, the two‐electrode tandem device showed ~3.5 mA cm −2 . These findings highlight the potential of tandem PEC devices as a sustainable and efficient solution for scalable green hydrogen production.