Conjugated Acetylenic Polymers Grafted Cuprous Oxide as an Efficient Z-Scheme Heterojunction for Photoelectrochemical Water Reduction

As attractive materials for photoeletrochemical hydrogen evolution reaction (PEC HER), conjugated polymers (e.g., conjugated acetylenic polymers [CAPs]) still show poor PEC HER performance due to the associated serious recombination of photogenerated electrons and holes. Herein, taking advantage of the in situ conversion of nanocopper into Cu₂O on copper cellulose paper during catalyzing of the Glaser coupling reaction, a general strategy for the construction of a CAPs/Cu₂O Z-scheme heterojunction for PEC water reduction is demonstrated. The as-fabricated poly(2,5-diethynylthieno[3,2-b]thiophene) (pDET)/Cu₂O Z-scheme heterojunction exhibits a carrier separation efficiency of 16.1% at 0.3 V versus reversible hydrogen electrode (RHE), which is 6.7 and 1.4-times higher respectively than those for pDET and Cu₂O under AM 1.5G irradiation (100 mW cm⁻²) in the 0.1 m Na₂SO₄ aqueous solution. Consequently, the photocurrent of the pDET/Cu₂O Z-scheme heterojunction reaches ≈520 µA cm⁻² at 0.3 V versus RHE, which is much higher than pDET (≈80 µA cm⁻²), Cu₂O (≈100 µA cm⁻²), and the state-of-the-art cocatalyst-free organic or organic-semiconductor-based heterojunctions/homojunctions photocathodes (1–370 µA cm⁻²). This work advances the design of polymer-based Z-scheme heterojunctions and high-performance organic photoelectrodes.