Evaluating the Effects of Surfactant Templates on the Electrocatalytic Activity and Durability of Multifaceted Platinum Nanostructures

High-surface-area multifaceted platinum (Pt) nanoparticles(NPs)exhibit promising electrocatalytic properties for various electrochemicalreactions. Effective structural and morphological control is a keyfactor in attaining improved electrocatalytic activities. Herein,we use low concentrations of surfactants (less than or similar to critical micelleconcentration) as templates during Pt electrodeposition to producemultifaceted Pt NPs and evaluate their electrochemical active surfacearea (A (ecsa)) and activity for the oxygenreduction reaction (ORR). The electrodeposition potentials for thenucleation and growth stages were optimized through an evaluationof the surface coverage and uniformity of the size of the electrodepositedparticles. The electrodeposition was performed in the presence ofa cationic (i.e., cetyltrimethylammonium bromide, CTAB), anionic (i.e.,sodium dodecyl sulfate, SDS), or non-ionic [i.e., polyoxyethylene(20) stearyl ether, Brij 78] surfactant. The deposited Pt NPs havethe mean diameter of 49 +/- 11 nm for Brij 78, 54 +/- 9 nm forCTAB, and 57 +/- 14 nm for SDS, with faceted crystallites exposedon their surfaces as observed using high-resolution transmission electronmicroscopy. The A (ecsa) of these Pt nanostructuresincreased when using surfactants as templates during electrodeposition;the A (ecsa) increased in the order of non-templatedPt (12.4 m(2) g(-1)) < Pt-CTAB (16.2 m(2) g(-1)) < Pt-SDS (17.1 m(2) g(-1)) < Pt-Brij 78 (20.4 m(2) g(-1)). The mass activities of Pt-CTAB, Pt-SDS, and Pt-Brij 78 towardthe ORR were also calculated to be, respectively, similar to 1.5, 1.6,and 2.0 times higher than that of non-templated Pt at 0.8 V (vs RHE).The Pt NPs electrodeposited in the presence of surfactants exhibitedstructural durability when subjected to a test of 5000 cycles of theapplied potential in a square wave form between 0.6 and 0.95 V (vsRHE). This comparative study offers several insights into the designof surfactant-assisted electrodeposition techniques for creating multifacetedPt with enhanced surface area and activity toward the ORR and electrocatalyticstability.

Automated summary

Low concentrations of surfactants were used as templates during Pt electrodeposition to synthesize high-surface-area multifaceted Pt nanoparticles. The electrochemical active surface area (A (ecsa)) and activity for the oxygen reduction reaction (ORR) were evaluated. The use of surfactants as templates during electrodeposition led to an increase in A (ecsa) and mass activity of the Pt nanostructures.