Atomic scale interaction between the water molecule and the Pd electrodes was investigated by the mechanically controllable break junction technique at cryogenic temperature. The interaction between the water molecule and the atomic scale Pd electrodes and the resultant formation of the single-molecule junction of the water molecule bridging the gap between the Pd electrodes were confirmed by vibrational spectroscopy where the water−Pd vibrational mode of 70 meV was identified. We found that no water dissociation occurred on the atomic scale Pd electrodes. The electronic transport measurement revealed that the water single molecule junction carried the electronic current in the ballistic transport regime and the conductance was determined to be 1 G 0 where G 0 is the conductance quantum. The length analysis and current-bias voltage measurement of the junction suggest that the single water molecule is connected to Pd atomic chain.
Water splitting is an essential process for converting light energy into easily storable energy in the form of hydrogen. As environmentally preferable catalysts, Cu‐based materials have attracted attention as water‐splitting catalysts. To enhance the efficiency of water splitting, a reaction process should be developed. Single‐molecule junctions (SMJs) are attractive structures for developing these reactions because the molecule electronic state is significantly modulated, and characteristic electromagnetic effects can be expected. Here, water splitting is induced at Cu‐based SMJ and the produced hydrogen is characterized at a single‐molecule scale by employing electron transport measurements. After visible light irradiation, the conductance states originate from Cu/hydrogen molecule/Cu junctions, while before irradiation, only Cu/water molecule/Cu junctions were observed. The vibration spectra obtained from inelastic electron tunneling spectroscopy combined with the first‐principles calculations reveal that the water molecule trapped between the Cu electrodes is decomposed and that hydrogen is produced. Time‐dependent and wavelength‐dependent measurements show that localized‐surface plasmon decomposes the water molecule in the vicinity of the junction. These findings indicate the potential ability of Cu‐based materials for photocatalysis.
What is the most significant result of this study?This study involved the comprehensive investigation of the structurea nd electron transport properties of metal atomic junctionsd oped with dichloroethylene. The interaction between the molecule and metal surface determined the trapping state of the molecule at the nanogap.I na ddition, the adsorbed dichloroethylene promoted the formation of linear atomic chains. https://educ.titech.ac.jp
In article number 2008109, Marius Buerkle, Satoshi Kaneko, Tomoaki Nishino, and co‐workers induce the water‐splitting reaction under visible light utilizing a copper‐based single‐molecule junction. A product (hydrogen) and a reactant (water‐molecule) are distinguished by the single‐molecule measurements techniques based on conductance measurement, inelastic electron tunneling spectroscopy, and the first‐principles calculations.
The front cover artwork was provided by the group of Prof. Nishino, Tokyo Institute of Technology. The image depicts the investigation of the structure and electron transport of the Au, Ag, Cu, Ni, Fe, and Pd atomic junctions doped with dichloroethylene. Read the full text of the Article at 10.1002/cphc.201900988.
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