The synthesis of sub-nano-thick pd nanobelt-based materials for enhanced hydrogen evolution reaction activity

Tailoring atomic structures of noblemetal nanomaterials with size close to single-unit cell range is essential in both fundamental researchand applications, including their development into high catalytic performance materials in renewable, green energy conversions, devices for energy storage, and as biosensors for environmental pollutants. However, several strategies used in fabricating these materials still impose enormous challenges, arising from lack of even size distribution, shape uniformity, and controlled composition, which are critical in determining their specific activities and efficiencies. Herein, we report a facile approach for preparing sub-nano-thick palladium nanobelt-based (PdNB) materials. Then we rationalized the formation mechanism of such highly anisotropic structures by morphology-related thermodynamic and kinetic analysis. Moreover, we investigated if electrocatalysis performance of these NB-basedmaterialswere enhanced.Thepalladium(Pd) NBs featured a thickness of ∼ 0.9-1.2 nm and width of 5-18nmwith length extending to severalmicrometers [denoted as Pd(0.9)], or a thickness of ∼ 0.7-0.9 nm and width of 2.5-6 nmwith length of several hundreds of nanometers [denoted as Pd(0.7)]. According to our theoretical analysis, one-dimensional (1D) growth encountered almost no energy barrier at optimal reaction conditions, whereas the growth of Pd nanostructures with other dimensions confronted high barriers, indicating that it was plausible to prepare 1D structures with sizes close to single-unit cells. Also, platinum (Pt) could be successfully doped into the Pd(0.9) NBs through a galvanic epitaxial growth, forming edge-Pt-enriched Pd NBs (eePtPd NBs). Further, electron transfer from Pd to Pt imparted the eePtPd NBs with high hydrogen evolution reaction (HER) activity. The eePtPd NBs showed a 3.5 and 1.8 times higher in exchange current density and mass activity (at-0.1 V), respectively,compared to those of Pt catalysts in perchloric acid (HClO4) solutions. Finally, the NBs all showed high activity toward ethanol and formic acid oxidation reactions. Our current work aids in gaining insights into tailoring Pd nanostructures at an atomic level and provides Pd sub-nanometric 1D structures for further research. Moreover, our morphology-related thermodynamic and kinetic analysis extend our understanding of the control of nanostructure morphology and might shed light on the precision of designing specific morphologies of noble metal nanocrystal structures.