Microwave Synthesis of Carbon‐Supported Cobalt Nickel Selenide Ternary Catalyst Toward the Oxygen Reduction Reaction

Abstract

AbstractCarbon supported cobalt nickel selenide (Co,Ni) Se2/C ternary catalysts were prepared by a simple microwave‐assisted polyol method. The effects of the Co amount (x), in terms of the Co content over the total amounts of Co and Ni presented in (CoxNi1‐x) Se2/C (x=0, 0.25, 0.33, 0.50, 0.67, 0.75 and 1.0), on the crystal structures, surface morphologies, microstructures, electrocatalytic activities and stabilities toward oxygen reduction reaction (ORR) were systematically investigated. It was found that the incorporation of Co into NiSe2/C apparently reduced the average crystallite sizes of the as‐prepared (CoxNi1‐x) Se2/C (0<x<1.0) ternary catalysts by forming the solid solution like structure composing of NiSe2 and CoSe2. The average crystallite sizes decreased from 32.1 nm to 20.6 nm by varying x from 0 to 1.0. A typical cubic (CoxNi1–x) Se2 (0≤x<1.0) single crystallite with pyramidal morphology was identified, which differed significantly from the predominant orthogonal CoSe2 polycrystallite at x=1.0. The potentials corresponding to ORR (EORR) were 0.50∼0.68 V with the electron transfer numbers of 2.1∼3.6 at 0.3 V in 0.1 mol L−1 HClO4 solutions. The enhanced ORR activities were observed with Co‐rich (CoxNi1–x) Se2/C catalysts (x>0.5), in particular, with (Co0.75Ni0.25) Se2/C which showed no loss in EORR after 1000 cycles. The excessive amount of Co introduced into NiSe2/C resulted in the coexistence of a cubic (CoxNi1‐x) Se2 single crystallite and an orthogonal CoSe2 polycrystallite, which might be beneficial to inhibit the grain growth and to provide more active sites. Furthermore, the formation of (CoxNi1‐x) Se2 might provide more stable structure for the ternary (Co0.75Ni0.25) Se2/C to impede the Se oxidation.