Hot-Injection Synthesis of PtCu₃ Concave Nanocubes with High-Index Facets for Electrocatalytic Oxidation of Methanol and Formic Acid

Extensive efforts have been devoted to tailoring the composition and shape of Pt nanomaterials for a high catalytic property. Herein, we report facile hot-injection synthesis of PtCu₃ concave nanocubes enclosed by high-index facets of {720}, {520}, and {320}. Cetyltrimethylammonium bromide (CTAB) and trinoctylphospine oxide (TOPO), as the structural-directing agents, play indispensable roles in the formation of concave nanocubes of PtCu₃. The introduction of Br^– from CTAB facilitates the galvanic replacement reaction on the {100} facets, which lead to formation of the concave structure; TOPO is essential to achieve the uniform cubic structure. The PtCu₃ concave nanocubes exhibit mass activity of 0.69 A mg_Pt^–1 and specific activity of 2.44 mA cm_Pt^–2 for methanol oxidation, which are 2.1 and 4.4 times higher than the commercial Pt/C, respectively; for formic acid oxidation they are 0.45 A mg_Pt^–1 and 1.57 mA cm_Pt^–2, and are 2.0 and 4.2 times higher than the commercial Pt/C, respectively. The PtCu₃ concave nanocubes and commercial Pt/C show the same onset potentials for methanol oxidation, whereas the onset potential on the PtCu₃ concave nanocubes for formic acid oxidation is negatively shifted by ca. 124 mV compared to that of the commercial Pt/C. It suggests that the PtCu₃ concave nanocubes are more sensitive to the electrocatalytic oxidation of formic acid than methanol. This superior electrochemical performance will inspire more investigations into the rational design of high-performance Pt-based electrocatalysts.