A photoactive process cascaded electrocatalysis for enhanced methanol oxidation over Pt-MXene-TiO 2 composite
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A photoactive process cascaded electrocatalysis for enhanced methanol oxidation over Pt-MXene-TiO2 composite Yue Sun§, Yunjie Zhou§, Yan Liu, Qingyao Wu, Mengmeng Zhu, Hui Huang, Yang Liu (), Mingwang Shao (), and Zhenhui Kang () Institute of Functional Nano and Soft Materials Laboratory (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, China § Yue Sun and Yunjie Zhou contributed equally to this work. © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 11 April 2020 / Revised: 16 May 2020 / Accepted: 30 May 2020
ABSTRACT Highly efficient photo-assisted electrocatalysis for methanol oxidation reaction (MOR) realizes the conversion of solar and chemical energy into electric energy simultaneously. Here we report a Pt-MXene-TiO2 composite for highly efficient MOR via a photoactive cascaded electro-catalytic process. With light (UV and visible light) irradiation, MXene-TiO2 serves as the photo active centre (photoinduced hole) to activate the methanol molecules, while Pt particles are the active centre for the following electro-catalytic oxidation of those activated methanol molecules. Pt-MXene-TiO2 catalyst exhibits a lower onset potential (0.33 V) and an impressive mass activity of 2,750.42 mA·mg−1Pt under light illumination. It represents the highest MOR activity ever reported for photo-assisted electrocatalysts. Pt-MXene-TiO2 also shows excellent CO tolerance ability and stability, in which, after long-term (5,000 s) reaction, still keeps a high mass activity of 1,269.81 mA·mg−1Pt (62.66% of its initial activity). The photo-electro-catalytic system proposed in this work offers novel opportunities for exploiting photo-assisted enhancement of highly efficient and stable catalysts for MOR.
KEYWORDS photoactive process, electrocatalysis, cascade, photoelectrochemistry, methanol oxidation reaction
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Introduction
Photo-electrocatalysts play a key role in clean energy conversion technologies. As a promising technology to convert chemical energy to electrical energy, with high utilization efficiency and environmental benignity, direct methanol fuel cells (DMFCs) have attracted substantial attentions [1–6]. Notably, high efficient photo-assisted electrocatalysis for methanol oxidation reaction (MOR) can realize the conversion of solar and chemical energy into electric energy simultaneously. To date, Pt-based materials were considered as the work-of-art MOR electrocatalysts in DMFCs, though they still suffer from several problems, such as high cost and easy CO poisoning [7–10]. Few pioneer work suggested the enhanced performance of methanol oxidation by introducing semiconductors into Pt-based catalyst with the assistance of light illumination [11–16]. For those twocomponent semiconductor/Pt catalysts, the slightly enhanced current density of methanol oxidation may be attributed to the photo-oxidation of small organic molecules including adsorbed methanol and intermediates generated during MOR [17, 18].
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