Engineering both intrinsic characteristic and local microenvironment of platinum sites toward highly efficient oxygen reduction reaction.

The optimization of the adsorption of oxygen-containing intermediates on platinum (Pt) sites of Pt-based electrocatalysts is crucial for the oxygen reduction reaction process. Currently, a large amount of researches mainly focus on modifying the bulk structure of the electrocatalysts, however, the vital role of solvent effect on the phase interfaces is often overlooked. Here, we successfully developed an electrocatalyst in which the ordered PtCo alloy anchors on the cobalt (Co) single-atoms/clusters decorated support (CoNC) and its surface is further optimized using hydrophobic ionic liquid (IL). Experimental studies and theoretical calculations indicate that compressive stress on Pt lattice contributed by intrinsic structure and the local hydrophobicity caused by IL on the surface can suppress the stabilization of *OH on Pt. This synergistic effect affords outstanding catalytic performance, exhibiting a half-wave potential (E) of 0.916 V vs. RHE and a mass activity (MA) of 1350.3 mA mg in 0.1 mol/L perchloric acid (0.1 M HClO) electrolyte, much better than the commercial Pt/C (0.849 V vs. RHE and 145.5 mA mg for E and MA, respectively). Moreover, the E of IL-PtCo/CoNC only lost 5 mV after 10,000 cyclic voltammetry (CV) cycles due to a strong and synergistic contact of the intermetallic PtCo alloy with the CoNC support and IL. This research provides an effective method for designing efficient electrocatalysts by combining intrinsic structure and surface modification.