Ternary BiVO 4 /NCQD/FeCo-LDH Photoanode with Light Capture and Hole Extraction Units for Efficient Photoelectrochemical Water Splitting

Rational construction of efficient composite photoanodes is crucial for improving photoelectrochemical (PEC) water oxidation and boosting the efficiency of solar hydrogen production. However, their performance is severely impeded by sluggish charge-separation-transfer and oxygen evolution reaction (OER) kinetics. Herein, we proposed a ternary BiVO4/NCQD/FeCo-LDH photoanode, which integrated nitrogen-doped carbon quantum dots (NCQD) as a light capture unit and FeCo layered double hydroxide (FeCo-LDH) as a hole extraction cocatalyst. NCQD broadened the visible light absorption, improved conductivity efficiency, and formed a typical type-Z heterojunction with BiVO4, while FeCo-LDH accelerated hole transfer and enhanced OER kinetics through its bimetallic active sites. Bulk-phase charge separation and surface charge injection efficiencies of the BiVO4/NCQD/FeCo-LDH photoanode reached 81.1% and 77.4%, respectively. The photocurrent density reached as high as 4.74 mA cm–2 at 1.23 V vs RHE. The solar-to-hydrogen (STH) conversion efficiency reached 1.2%, representing a 6-fold improvement over pristine BiVO4. This work offered a rational design strategy for high-performance photoanodes by synergistically combining light capture and hole extraction functionalities to enhance the efficiency of PEC water splitting.