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

Abstract

Abstract Carbon supported cobalt nickel selenide (Co,Ni) Se 2 /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 (Co x Ni 1 ‐x ) Se 2 /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 NiSe 2 /C apparently reduced the average crystallite sizes of the as‐prepared (Co x Ni 1 ‐x ) Se 2 /C (0 <x< 1.0) ternary catalysts by forming the solid solution like structure composing of NiSe 2 and CoSe 2 . The average crystallite sizes decreased from 32.1 nm to 20.6 nm by varying x from 0 to 1.0. A typical cubic (Co x Ni 1 –x ) Se 2 (0≤ x <1.0) single crystallite with pyramidal morphology was identified, which differed significantly from the predominant orthogonal CoSe 2 polycrystallite at x= 1.0. The potentials corresponding to ORR ( E ORR ) 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 HClO 4 solutions. The enhanced ORR activities were observed with Co‐rich (Co x Ni 1 –x ) Se 2 /C catalysts ( x >0.5), in particular, with (Co 0.75 Ni 0.25 ) Se 2 /C which showed no loss in E ORR after 1000 cycles. The excessive amount of Co introduced into NiSe 2 /C resulted in the coexistence of a cubic (Co x Ni 1 ‐x ) Se 2 single crystallite and an orthogonal CoSe 2 polycrystallite, which might be beneficial to inhibit the grain growth and to provide more active sites. Furthermore, the formation of (Co x Ni 1 ‐x ) Se 2 might provide more stable structure for the ternary (Co 0.75 Ni 0.25 ) Se 2 /C to impede the Se oxidation.