The CO-assisted thermal decomposition of a new, surfactant-ligated Pt precursor, [Pt(acac)(NHR)](n) (n = 2, 3; R = C(18)H(37)), gives structurally uniform five-fold twinned Pt nanorods. The Pt nanorods, mostly covered by {100} facets, exhibit much enhanced electrocatalytic activity over {100} faceted Pt nanocubes, indicating the superior catalytic performance due to the presence of the reactive twinning interface.