Boost reactivity of tri-iodide reduction electrode by highly faceted octahedral PtNi nanocrystals

PtNi octahedra were utilized as the counter electrodes (CEs) of N719-dye based DSSCs and well characterized via high-resolution transmission electron microscopy, powder x-ray pattern scan, and on-axis transmission Kikuchi Diffraction technique, rendering the crystallographic orientation of individual particle. The photovoltaic results show that the power conversion efficiency (PCE) of devices with different CEs is in the following sequence: Pt thin film < Pt7Ni3 octahedra < Pt5Ni5 octahedra Pt4Ni6 octahedra. The device of Pt4Ni6 octahedra reveal the PCE over 10%. The electrochemical measurements show the tri-iodide reduction activity is in a sequence of Pt4Ni6 octahedra Pt5Ni5 octahedra > Pt7Ni3 octahedra > Pt thin film. This study provides fundamental understanding of the exposed surface of PtNi octahedra, for which the coverage of {111} facets plays a key role in the tri-iodide reduction and thereby leads to the increase of device PCE with significant decrease of the Pt component in CEs. (C) 2021 Elsevier Inc. All rights reserved.