Mechanochemical synthesis and application of mixed-metal copper–ruthenium HKUST-1 metal–organic frameworks in the electrocatalytic oxygen evolution reaction†
Linda Sondermann, Quentin Smith, Till Strothmann, Annette Vollrath, Thi Hai Yen Beglau and Christoph Janiak
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引用次数: 0
Abstract
Novel electrode materials for electrocatalytic hydrogen generation are investigated for increasing the activity of expensive noble-metal components. Here various mixed-metal copper–ruthenium combinations of the metal–organic framework (MOF) HKUST-1 (HKUST = Hong Kong University of Science and Technology, with the formula [Cu3(BTC)2(H2O)3]n (BTC = benzene-1,3,5-tricarboxylate)) as CuxRu-BTC were synthesized through a mechanochemical method. This mechanochemical method allowed for gram-scale synthesis of the mixed-metal MOFs in a one-hour synthesis time. Characterization through powder X-ray diffraction (PXRD), N2-adsorption, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared (FT-IR) spectroscopy confirmed the formation of a MOF with the HKUST-1 topology, albeit with lower porosity compared to neat HKUST-1. The synthesized MOFs were tested as precursor materials for catalysts for the oxygen evolution reaction (OER) and performed comparably to the industry standard ruthenium oxide (RuO2). An overpotential (η) of 314 mV (RuO2η = 312 mV), a Tafel slope (b) of 55 mV dec−1 (RuO2b = 47 mV dec−1) was achieved which in combination with a charge-transfer resistance (RCT) of 13.6 Ω (RuO2RCT = 52.8 Ω) and a faradaic efficiency (FE) of 70% (RuO2 FE = 66%) supports the derived catalyst from Cu10Ru-BTC with an intimate mixture of copper and ruthenium at the nanoscale to be effective for the OER having lower ruthenium content than RuO2. All derived catalysts from the CuxRu-BTC samples and RuO2 showed good stability in a chronopotentiometric measurement over 12 h.