From nano to macro: Hierarchical platinum superstructures synthesized using bicontinuous microemulsion for hydrogen evolution reaction

• Published in: Electrochimica acta 2020-09, Vol.354, p.136608, Article 136608
• Main Authors: Adesuji, Elijah T., Khalil-Cruz, Laila E., Videa, Marcelo, Sánchez-Domínguez, Margarita
• Format: Article
• Language: English
• Subjects: Bicontinuous microemulsion; Charge transfer; Crystallites; Electrocatalyst; Electrochemical analysis; Electrochemical impedance spectroscopy; HER; Hydrogen evolution reactions; Microemulsions; Nanoreactor; Platinum; Precursors; Pt hierarchical superstructure; Reducing agents; Superstructures; Water chemistry
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2020.136608

The possibility to harness the intrinsic properties of bicontinuous microemulsions (BCME) has led to their application as nanocages in the synthesis of nanocoral-shaped Pt hierarchical superstructures (PtHSs). We employed two different platinum precursors (oil-soluble and water-soluble) and sodium borohydride (NaBH4) was used as reducing agent. PtHSs were observed to be pure and nanocrystalline, with small crystallite size (4.5–6.5 nm). XPS showed that the nanostructures are composed of Pt (0). The electrochemical surface areas obtained were 8.7 m2/g, 35.1 m2/g and 20.9 m2/g for PtH–O (synthesized using oil-soluble precursor), PtH-A2 and PtH-A4 (synthesized using 2 and 4% water-soluble Pt precursor), respectively. Linear sweep voltammetry (LSV), Tafel plots and electrochemical impedance spectroscopy (EIS) were used to study the hydrogen evolution reaction process. PtH-A2 showed an overpotential of 68 mV at 10 mA cm−2, a Tafel slope of 30 mV dec−1 and a low charge transfer resistance of 3.39 Ω. The stability of the PtHSs was tested before and after 1000 LSV cycles with minimal loss of current density. The improved electrochemical properties recorded, are due to the unique Pt hierarchical superstructure, which is key for the electrocatalytic performance. Through this research, the “template effect” of bicontinuous microemulsions towards the synthesis of metallic hierarchical superstructures is demonstrated for the first time. [Display omitted] •1st report of Pt hierarchical superstructure synthesis in bicontinuous microemulsion.•Nano-meso-macrostructure of Pt electrocatalyst from soft and facile synthesis.•Morphology depends on the type of Pt precursor (lipo- or hydrosoluble).•Efficient and stable electrocatalytic performance for hydrogen evolution reaction.