Interfacial modulation of platinum electrodeposition by Tween 80: Mechanistic insights into nucleation and oxygen reduction behavior

Abstract

The oxygen reduction reaction at the cathode constitutes the rate-determining electrochemical process in proton exchange membrane fuel cells, necessitating precise control over platinum catalyst structure and surface chemistry. In this study, platinum catalysts were prepared by cyclic voltammetric electrodeposition on a platinum-substrate using a mixed-acid electrolyte, while systematically varying the concentration of the nonionic surfactant Tween 80. The influence of surfactant addition on platinum electrocrystallization was investigated through a combined analysis of nucleation kinetics, surface morphology, and ORR activity. Electrochemical characterization under inert and oxygen-saturated conditions, together with scanning electron microscopy, demonstrates that Tween 80 concentration critically governs the transition between distinct nucleation and growth regimes. At low surfactant content (0.05% (v/v) Tween 80), weak and transient interfacial interactions favor homogeneous nucleation and compact film formation, leading to the highest intrinsic ORR activity even if a moderate electrochemical surface area. Beside, increasing the surfactant concentration toward a micelle-influenced regime (0.15% (v/v) Tween 80) promotes granular morphologies with elevated apparent surface area but diminished intrinsic activity, while excessive surfactant loading (1.00% (v/v) Tween 80) induces pronounced transport limitations and active-site blockage. The results indicate that optimal ORR performance is governed not solely by surface area enhancement but by controlled modulation of interfacial adsorption and ion transport during electrodeposition.