PTB7:PC₆₁BM Bulk Heterojunction-Based Photocathodes for Efficient Hydrogen Production in Aqueous Solution

Because of excellent light absorption and charge separation properties, a polymer bulk heterojunction (BHJ) composed of electron-donor and electron-acceptor is very promising to be used for photoelectrode preparation. In this work, a PTB7:PC₆₁BM BHJ-based photocathode is fabricated for photoelectrochemical (PEC) hydrogen evolution reaction (HER) in aqueous solution. With CuO_x and TiO_x thin films as interfacial modification layers, the photocathode with full structure (fluorine-doped tin oxide/CuO_x/PTB7:PC₆₁BM/TiO_x/Pt) generates a maximum photocurrent density up to -7.27 mA cm^-2 and an onset potential as positive as 0.63 V. The half-cell solar-to-hydrogen efficiency is up to 1.5%, outperforming all of the previous BHJ-based photocathodes for HER. CuO_x is identified to play a role of facilitating charge separation, whereas TiO_x improves the charge injection as well as blocks the back migration of holes during the PEC process. The factors including permeation of water and oxygen molecules, incident light spectrum, and current flowing that affect the PEC stability are investigated and discussed.