Self-stabilization of zero-dimensional PdIr nanoalloys at two-dimensional manner for boosting their OER and HER performance.

Zero-dimensional PdIr nanoalloys self-assembed to porous nanosheets with the help of capping agent PDDA. The PdIr PNS shows excellent OER and HER catalitic activities. • A simple route was used to self-stabilize ultrathin 0D PdIr nanocrystals into freestanding 2D porous PdIr nanosheets (PdIr PNSs). • The PdIr PNSs possessed large surface area-to-volume ratio and high density of exposed atoms. • The PdIr PNSs delivered excellent catalytic activities and stabilities. It remains a grand challenge to transform zero-dimensional (0D) noble-metal building blocks into well-defined two-dimensional (2D) architectures, which normally lacking an intrinsic driving force for anisotropic permutation in 2D manner. Herein, we report the first example of using a simple but efficient hydrothermal route to synthesize and self-stabilize ultrathin 0D PdIr NCs (2.4 nm) into a new class of freestanding 2D porous PdIr nanosheets with lateral size up to 1.5 μm (PdIr PNSs). Distinguished from previously reported 2D noble-metal nanosheets, the resultant 2D PdIr PNSs with immense surface area-to-volume ratio and high density of exposed atoms largely retain the special natures of 0D PdIr building blocks and further optimize their catalytic activity and stability at 2D manner. Electrochemical studies show that 2D PdIr PNSs deliver both excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities with an HER overpotential of 40 mV and an OER overpotential of 285 mV affording 10 mA cm−2, outperforming those of 0D PdIr building blocks. The present work highlights the importance of tuning 0D nanocrystals at 2D manner for enhancing their OER and HER performance. [ABSTRACT FROM AUTHOR]