Significant Improvements on BiVO₄@CoPi Photoanode Solar Water Splitting Performance by Extending Visible-Light Harvesting Capacity and Charge Carrier Transportation

Efficient light harvesting and transfer of photogenerated charge carriers between the photoanode and the O2 evolution catalyst are crucial for robust photoelectrochemical (PEC) water splitting. Herein, we present a simple strategy to improve the light harvesting capability and the hole transfer efficiency by anchoring dithiooxamide-derived N, S co-doped carbon nanosheets (NSCN) as a visible-light harvester and polyaniline (PANI) as a hole transfer layer from BiVO4 to CoPi. The resultant BiVO4-NSCN/PANI@CoPi photoanode exhibits the stable photocurrent density of 4.46 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (VRHE) under 1 sun illumination. The applied bias photon-to-current efficiency (ABPE) is measured to be 1.13% at 0.74 VRHE. The photocurrent density and the ABPE are significantly higher than the previous BiVO4 photoanodes. In addition to the high photocurrent density, the photoanode exhibits excellent stability, where the photocurrent density decreases by only 3% over 10 h. Systematic experimental studies reveal that controlled thin layers of NSCN and PANI contribute to efficient light harvesting and charge transfer between BiVO4 and CoPi, resulting in a high photocurrent density and stability. We believe that the proposed approach is effective for the design of efficient and stable photoanodes for PEC water splitting.