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. A conjugated acetylenic polymers (CAPs)/cuprous oxide Z‐scheme heterojunction is fabricated by a general nanocopper‐mediated Glaser polycondensation strategy based on in situ conversion of nanocopper into Cu2O in the growth of the CAPs. Eventually, the as‐fabricated poly(2,5‐diethynylthieno[3,2‐b]thiophene) (pDET)/Cu2O Z‐scheme heterojunction substantially facilitates charge separation/transfer and exhibits state‐of‐the‐art performance for photoelectrochemical hydrogen evolution.