Metal nanostructures with an ultrathin Pt skin and abundant surface defects are attractive for electrocatalytic applications owing to the increased utilization efficiency of Pt atoms and the presence of highly reactive sites. This paper reports a conformal, layer-by-layer deposition of Pt atoms on defective Rh nanowires for the faithful replication of surface defects (i.e., grain boundaries) on the Rh nanowires. The thickness of the Pt shell can be controlled from one monolayer up to 5.3 atomic layers. This series of Rh@Pt n L ( n = 1–5.3) core–sheath nanowires show greatly enhanced activity and durability in catalyzing the ethanol oxidation reaction in an acidic medium. Among others, the Rh @ Pt 3.5L nanowires show the greatest mass activity (809 mA mg −1 Pt ) and specific activity (1.18 mA cm −2 ) after loaded on carbon support, which are 3.7 and 3.4 times those of the commercial Pt/C, respectively. In situ Fourier transform infrared spectroscopy studies indicate an enhanced interaction between the outermost Pt layer and the Rh nanowire can promote C C bond cleavage for complete oxidation of ethanol to CO 2 while depress the dehydrogenation of ethanol to acetic acid. As the Pt shell thickness is increased, the selectivity for the CO 2 pathway decreases while that for acetic acid is increased.
Xue Jiang,Zemeng Dong,Qiong Zhang,Guang-Rui Xu,Jianping Lai,Zhenjiang Li,Lei Wang
The electrochemical oxidation of ethylene glycol (EG), which is favorable for replacing the sluggish oxygen evolution reaction (OER) in thermodynamics, realizes energy-saving hydrogen evolution and also produces high-value chemical products of glycolic acid. Under the guidance of this concept, PtRh nanowires with Rh atom modification (PtRh0.02@Rh NWs), which exhibited excellent properties during the hydrogen evolution reaction (HER) and ethylene glycol evolution reaction (EGOR), were designed and synthesized by controlling the reduction rate of metal precursor through a simple one-step solvothermal reduction. The interface strain effect produced by the metal co-doping effectively adjusted the electronic structure, contributing to introducing the heteroatom active center and inducing lattice strain, thereby achieving excellent electrocatalytic performance. The obtained PtRh0.02@Rh NWs exhibited excellent HER property with an extremely low overpotential of 30.6 and 45.8 mV, and Tafel slope of 39.1 and 39.5 mV dec−1 in alkaline water and seawater electrolytes, respectively, as well as outstanding EGOR properties with peak current density of 1.25 and 1.17 A mg−1, respectively. Additionally, the PtRh0.02@Rh NWs showed superior stability compared to that of commercial platinum black obtained from Johnson Matthey Corporation (JM-Pt black). When using PtRh0.02@Rh NWs as biofunctional materials for the HER in the cathode and the EGOR in the anode, a cell voltage of only 0.66 V for PtRh0.02@Rh NWs (HER)‖PtRh0.02@Rh NWs (EGOR) achieved a current density of 10 mA cm−2, which was much smaller than that of PtRh0.02@Rh NWs (HER)‖PtRh0.02@Rh NWs (OER) at 1.57 V. The results of electrochemical in situ Fourier transform infrared (FTIR) spectroscopy showed that the synthesized PtRh0.02@Rh NWs promoted the production of high-value glycolic acid when EG was dehydrogenated to form C2 intermediates. The Rh atoms modified on the surface of the Pt nanowires provided an effective strain effect to optimize the active sites, which creates a universal strategy for the design of highly efficient and durable bifunctional catalysts.
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