Dual (oxy)hydroxide Cocatalyst Synergistically Boosts Solar Water Splitting of BiVO4 Photoanode

Abstract Bismuth oxide (BiVO 4 ) is considered one of the most promising semiconductors for photoelectrochemical (PEC) water splitting due to its highly theoretical photocurrent of 7.5 mA cm −2 . However, its sluggish kinetics and severe photocorrosion still hinder the real application of a large‐area BiVO 4 photoanode. Herein, a room‐temperature immersion method has been used to fabricate a dual cocatalyst‐coated BiVO 4 film, namely the BiVO 4 /FeOOH/Co(OH) 2 photoanode. This composite photoanode delivers a photocurrent density of 2.56 mA cm −2 , which is 2.7 times that of pure BiVO 4 . After a long‐term testing of 10 h, its retention rate of photocurrent reaches 71.63 %, which is 4.6 times that of BiVO 4 . The kinetic studies illustrate that dual cocatalyst can significantly lower the charge transfer resistance, improve the charge injection efficiency, and reduce the Tafel slope. Specifically, FeOOH plays a role in transporting photogenerated holes, while Co(OH) 2 facilitates water oxidation reactions. In addition, the dual cocatalyst coating can slow down vanadium ion dissolution and improve PEC stability. This immersion method can easily be applied to large‐area photoelectrodes.