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Abstract Electrocatalytic oxygen reduction reaction (ORR) to prepare H2O2 in acidic medium has the advantages of green, safety, and portability, which shows broad development prospects. However, it still suffers from low catalyst activity, insufficient selectivity, and high cost. Herein, Pt1/CoSe2 with ultralow 0.01 wt.% Pt atomic distribution was synthesized by a simple hydrothermal method. The Pt1/CoSe2 with ultralow Pt content exhibits high activity, high selectivity, and long‐term stability for ORR to H2O2 in O2‐saturated 0.1 M HClO4. The onset potential is as low as 0.75 V versus reversible hydrogen electrode (RHE), H2O2 selectivity is as high as 84% (0.4 V vs. RHE), and the electron transfer number is 2.3 (0.4 V vs. RHE). Moreover, the hydrogen peroxide yield using the flow cell testing is 110.02 mmol gcat.−1 h−1 with high Faradaic efficiency of 78% (0 V vs. RHE) at 0.1 M HClO4, and the catalyst did not deactivate significantly after 60 h stability testing. Mechanistic studies and in situ X‐ray photoelectron spectroscopy characterization confirm that the ultralow Pt content on CoSe2 can effectively regulate the electronic structure of Co as the real active site around the Pt site, which gives a suitable ∆dp value (the difference between the d‐band center of the active metal site and the p‐band center of the terminal oxygen in *OOH), provides an ideal *OOH binding energy, and inhibits the O–O bond breakage. This work successfully improves the intrinsic activity of the Co active sites around Pt in Pt1/CoSe2 for acidic ORR to H2O2 by constructing ultralow‐content Pt single atom. |
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