Search

Polymer semiconductor with bulk heterojunction (BHJ) structure has attracted increasing attention to fabricate highly efficient photoelectrode for converting solar energy and water into hydrogen, thanks to its high photocurrent output and positive onset potential beyond 0.6 V. However, BHJ‐based photoelectrodes demonstrate poor anticorrosion against irradiation in aqueous environment, thus the photoelectrochemical (PEC) stability is a very intractable problem to solve. Herein, an inside and outside integrated modification method is developed to help BHJ‐based photocathode withstand PEC erosion during hydrogen production in acidic solution. The obtained BHJ (PBDB‐T:ITIC:PC71BM)‐based photocathode with surface carbon protective layer allows sustained and fast PEC hydrogen evolution (an average photocurrent density up to 13.5 mA cm−2) for a duration up to 15 h, which is among the best results of BHJ‐based photocathodes. The internal modification with fullerene derivative of PC71BM boosts the photogenerated electron transfer to balance against relative fast hole transfer, which largely alleviates electron accumulation and improves PEC intrinsic stability as a result. The surface carbon layer effectively resists the permeation of aqueous electrolyte without hindering interfacial charge transfer. This metal‐free protective method is very promising toward construction of highly robust BHJ‐based photoelectrodes for sustainable water splitting. [ABSTRACT FROM AUTHOR]

Ferrihydrite (Fh) has been demonstrated as an effective interfacial layer for photoanodes to achieve outstanding photoelectrochemical (PEC) performance for water oxidation reaction owing to its unique hole‐storage function. However, it is unknown whether such a hole‐storage layer can be used to construct highly efficient photocathodes for hydrogen evolution reaction (HER). In this work, we report Fh interfacial engineering of amorphous silicon photocathode (with nickel as HER cocatalyst) achieving a photocurrent density of 15.6 mA cm−2 at 0 V vs. the reversible hydrogen electrode and a half‐cell energy conversion efficiency of 4.08 % in alkaline solution, outperforming most of reported a‐Si based photocathodes including multi‐junction configurations integrated with noble metal cocatalysts in acid solution. Besides, the photocurrent density is maintained above 14 mA cm−2 for 175 min with 100 % Faradaic efficiency for HER in alkaline solution. Our results demonstrate a feasible approach to construct efficient photocathodes via the application of a hole‐storage layer. [ABSTRACT FROM AUTHOR]

Highly efficient photocathode with onset potential beyond 0.6 V is very desirable in order to construct photoelectrochemical (PEC) device for stand‐alone overall water splitting. In this work, it is reported a nonfullerene PBDB‐T:ITIC bulk heterojunction (BHJ) based photocathode delivering unprecedented positive onset potential of 0.8 V and optimal photocurrent density of −11.7 mA cm−2 at 0 V in pH 1 solution. The yielded high ideal ratiometric power‐saved efficiency (Φsaved,ideal) of 4.1% is a record among the previous organic photocathodes. When the electrolyte pH moves to neutral, the Φsaved,ideal is still to be 3.2%, yet being twice more than the currently reported highest value. Pairing with TiOx, the hole transport layer of CuOx with more efficient charge carrier transportation and hole extraction ability excels MoO3 and NiOx, contributing to the highly efficient solar hydrogen production in both acidic and neutral solutions. Premixing the BHJ blend precursor with an anti‐oxidative agent is proved to be a beneficial strategy to improve the PEC stability by suppressing the photo‐oxidation degradation of organic polymer materials. Subsequently a conceptual PEC cell comprising of tandem CuOx/BHJ/TiOx/Pt photocathode and BiVO4/NiFeOx photoanode with a high solar‐to‐hydrogen efficiency up to 1.1% is fabricated in neutral solution without assistance of extra bias. [ABSTRACT FROM AUTHOR]