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

Abstract 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.