Elektrokimyasal hidrojen üretimi ve oksijen indirgeme tepkimeleri için katalizör olarak gümüş/platin çekirdek/kabuk nanoparçacıklarının akılcı tasarımı

Pt based electrodes are used in the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) owing to their stability and high efficiency with low overpotential. However, the amount of Pt used in the electrocatalysts should be reduced by preserving their catalytic efficiency so that Pt based electrodes find more widespread use in commercial applications. To achieve this goal, the reduction of particle size of Pt electrocatalysts is a promising way, but there are still a high percent catalytically intact Pt atoms remained in the core of small Pt NPs. In this respect, instead of using monometallic Pt NPs, the rational design of Pt core-shell NPs is highly promising because a cheaper metal is used in the core and less amount of Pt with higher efficiency is used as a shell and thus overall activity can be enhanced due to structural changes. For this purpose, in this study, we synthesized Ag/Pt core/shell NPs by using surfactant-assisted solvothermal method and then assembled the yielded Ag/Pt core/shell NPs on commercially available high surface area carbon support. The performance of as-prepared C-Ag/Pt and Pt hollow catalysts that is obtained by the acid-treatment of C-Ag/Pt were tested in HER and ORR. In order to modify Pt from core/shell structure, two methods, chemical etching and electrochemical leaching, were applied to remove Ag from the core. Pt hollow structures were obtained via chemical leaching whereas electrochemical leaching gave featureless NPs. Electrochemical activity tests revealed that both electrochemical and chemical leaching gives higher activity in HER in acidic electrolyte. More specifically, the cathodic activity for HER shows that the overpotential required to obtain -10 mA/cm2 is reduced by 35 mV for electrochemically leached Pt NPs while it is 85 mV for chemically leached Pt NPs. In both HER and ORR, the structural changes in the surface region are more effective to tune the activity rather than the Pt amount. Improved activity is associated with the modified electronic properties of the Pt skin layer which can also be adjusted by proper selection of particle size.