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Author: Feng, Xinliang × Author: Neumann, Christof × End date: 2024 × Start date: 2020 × DDC: 540 × WGL Institute: IFWD ×

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    Thiophene-Based Conjugated Acetylenic Polymers with Dual Active Sites for Efficient Co-Catalyst-Free Photoelectrochemical Water Reduction in Alkaline Medium
    (Weinheim : Wiley-VCH, 2021) Borrelli, Mino; Querebillo, Christine Joy; Pastoetter, Dominik L.; Wang, Tao; Milani, Alberto; Casari, Carlo; Khoa Ly, Hoang; He, Fan; Hou, Yang; Neumann, Christof; Turchanin, Andrey; Sun, Hanjun; Weidinger, Inez M.; Feng, Xinliang
    Although being attractive materials for photoelectrochemical hydrogen evolution reaction (PEC HER) under neutral or acidic conditions, conjugated polymers still show poor PEC HER performance in alkaline medium due to the lack of water dissociation sites. Herein, we demonstrate that tailoring the polymer skeleton from poly(diethynylthieno[3,2-b]thiophene) (pDET) to poly(2,6-diethynylbenzo[1,2-b:4,5-b′]dithiophene (pBDT) and poly(diethynyldithieno[3,2-b:2′,3′-d]thiophene) (pDTT) in conjugated acetylenic polymers (CAPs) introduces highly efficient active sites for water dissociation. As a result, pDTT and pBDT, grown on Cu substrate, demonstrate benchmark photocurrent densities of 170 μA cm−2 and 120 μA cm−2 (at 0.3 V vs. RHE; pH 13), which are 4.2 and 3 times higher than that of pDET, respectively. Moreover, by combining DFT calculations and electrochemical operando resonance Raman spectroscopy, we propose that the electron-enriched Cβ of the outer thiophene rings of pDTT are the water dissociation active sites, while the −C≡C− bonds function as the active sites for hydrogen evolution. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
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    Molecularly Engineered Black Phosphorus Heterostructures with Improved Ambient Stability and Enhanced Charge Carrier Mobility
    (Weinheim : Wiley-VCH, 2021) Shi, Huanhuan; Fu, Shuai; Liu, Yannan; Neumann, Christof; Wang, Mingchao; Dong, Haiyun; Kot, Piotr; Bonn, Mischa; Wang, Hai I.; Turchanin, Andrey; Schmidt, Oliver G.; Shaygan Nia, Ali; Yang, Sheng; Feng, Xinliang
    Overcoming the intrinsic instability and preserving unique electronic properties are key challenges for the practical applications of black phosphorus (BP) under ambient conditions. Here, it is demonstrated that molecular heterostructures of BP and hexaazatriphenylene derivatives (BP/HATs) enable improved environmental stability and charge transport properties. The strong interfacial coupling and charge transfer between the HATs and the BP lattice decrease the surface electron density and protect BP sheets from oxidation, resulting in an excellent ambient lifetime of up to 21 d. Importantly, HATs increase the charge scattering time of BP, contributing to an improved carrier mobility of 97 cm2 V-1 s-1 , almost three times of the pristine BP films, based on noninvasive THz spectroscopic studies. The film mobility is an order of magnitude larger than previously reported values in exfoliated 2D materials. The strategy opens up new avenues for versatile applications of BP sheets and provides an effective method for tuning the physicochemical properties of other air-sensitive 2D semiconductors.