High-index facet PtNi nanocrystals encapsulated in polydopamine derived carbon nanofilm for durable hydrogen...

Pt based materials are the most efficient catalysts for hydrogen evolution reaction (HER). However, the high cost and low earth abundance severely retard its commercial applications. Moreover, degradation of noble metal materials inevitably occurs during long-term HER process, especially in acidic media. Herein, core-shell structured high-index facet PtNi nanocrystals (HIF-PtNi NCs) coated with a polydopamine derived carbon nanofilm (cPDA) were fabricated for HER with enhanced catalytic activity and significantly improved stability to minimize Pt loadings. HIF-PtNi NCs possess a uniform concave morphology with average diameter of ∼42 nm in which the predominantly exposed crystal lattices spacing is 0.196 nm that is attributed to the (200) planes. The exposed high-energy surfaces exhibit better HER performance than low-energy surfaces such as commercial Pt/C catalyst and can reduce Pt loadings for commercial applications. Experiments and density functional theory (DFT) calculations confirmed that the amorphous carbon nanofilm significantly inhibited the deformation and degradation of the HIF-PtNi NCs catalyst in the core. HIF-PtNi NCs coated with cPDA nanofilm (HIF-PtNi NCs/cPDA) exhibits the HER overpotentials of 42 mV and the Tafel slope of 36.3 mV dec^-1 at current density of 10 mA cm^-2 with a low Pt loading of 140 μg cm^-1. HIF-PtNi NCs/cPDA shows almost no decay in HER activity after an accelerated durability test that conducted at a current density of 150 mA cm^-2 for 100 h in 0.5 M H₂SO₄ solution.