Visible Light-Driven Synthesis of PtCu Alloy Nanodendrites for Electrocatalytic Nitrogen-Conversion Reactions

Abstract

Hierarchical metal alloy nanostructures with branched morphologies are highly desirable for electrocatalysis due to their large surface area, highly exposed active sites and stability for catalytic reactions. In this work, the successful synthesis of uniformly-sized, spherical Pt–Cu alloy nanodendrites are reported using a novel visible light-driven photoreduction method that exploits fluorescein as an excited state photosensitizer. Factors influencing the structure and morphology of the PtCu alloy nanodendrites are systematically explored, including pH, Pt⁴⁺ and Cu²⁺ concentrations, Pt:Cu molar ratio, Light emitting diode (LED) light irradiation time, light intensity, concentration of hexadecyl trimethyl ammonium bromide (CTAB), and concentration of triethylamine (TEA). The experiments reveal a simultaneous photoreduction/galvanic replacement mechanism for PtCu alloy nanodendrite formation. Importantly, the PtCu alloy nanodendrites are easily separable from the reaction solution, facilitating their use as electrocatalysts for the electrocatalytic nitrite reduction reaction (eNO₂RR) to ammonia and also the nitrogen oxidation reaction (NOR) to nitrate. The PtCu alloy nanodendrites outperforms a commercially available Pt nanoparticle catalyst in both NO₂RR and NOR, validating the approach.