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

Abstract

Carbon 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.

Se Atom Doping Enhances the Catalytic Activity of Co@NC for Oxygen Reduction Reaction

“…Se atoms can provide an effective ORR active site. [41] The best ORR activity was reached when the pyrolysis temperature was continuously increased to 1000 °C. This may be because the pyrolysis temperature was high enough to evaporate a large amount of Zn from the ZIF-8 precursor, leaving enough microporous structures to host more active sites and reducing the bonding of Zn to Se to avoid the loss of Se-C active sites, while the temperature was high enough to facilitate the full reduction of SeO 2 and also to form more graphitic N. The Tafel slope was used to probe the kinetic process of oxygen reduction as shown in Figure 5c,d.…”

“…Notably, both Co@NC and Se@NC showed poor catalytic activity in acidic and alkaline electrolytes, but when introduce the Se atoms into Co@NC catalyst to constructed Co–Se@NC catalyst, their half‐wave potentials increased significantly, indicating that the joint action of Co and Se diatoms can greatly enhance the oxygen reduction activity of the catalysts under acidic and alkaline conditions, and the half‐wave potentials of Se@NC catalysts were significantly enhanced compared with those of NC catalysts, which can indicate that the introduction of Se atoms can provide an effective ORR active site. [ 41 ] The best ORR activity was reached when the pyrolysis temperature was continuously increased to 1000 °C. This may be because the pyrolysis temperature was high enough to evaporate a large amount of Zn from the ZIF‐8 precursor, leaving enough microporous structures to host more active sites and reducing the bonding of Zn to Se to avoid the loss of Se–C active sites, while the temperature was high enough to facilitate the full reduction of SeO 2 and also to form more graphitic N. The Tafel slope was used to probe the kinetic process of oxygen reduction as shown in Figure 5c,d.…”

Supported nanocatalysts: recent developments in microwave synthesis for application in heterogeneous catalysis

“…178 These ratios were equivalent to 47.21 % and 48.2 % of total amounts of FeSe 2 and FeSe. The increase in Co content in a series of ternary (Co x Ni 1-x )Se 2 /C catalysts improved the electrocatalytic activities towards ORR 198. The beneficial effect of Co incorporation was further reaffirmed by the increase of ORR potential (E ORR ).…”

“…Fair number of attempts have also been made to prepare supported simple metal oxide (CoO x , Co 3 O 4 , NiO, Fe 3 O 4 , SnO 2 , CeO 2 , TiO 2 ) nanocatalysts for application in petrochemical industry. 75,[160][161][162][163][164][165][166] In order to improve the catalytic activity as well as versatility in application potential of simple metal or metal oxide nanocatalysts, investigations on supported bimetal, [171][172][173][174][175][177][178][179][180][181][182][183][184][185][186][187] mixed metal oxide [188][189][190][191][192][193]196,197 and ternary metal 198,199 nanocatalysts are also available. MW assisted synthesis has been claimed to be economically viable short green method to produce supported nanocatalyst.…”

“…In this regard, anchoring or mobilization of nanocatalyst to inert or catalytically active support could help to improve the catalyst life time through inhibiting leaching, enhancing stability, less poisoning and maintaining the nano-size distribution. 81,87,88,[90][91][92]95,99,111,112,132,141,142,145,146,158,162,166,[171][172][173][175][176][177][178][179][180]182,183,186,190,198,199 MW assisted reduction in presence of reducing agents or under H 2 pressure, 98,[106][107][108][109]116,121,[127][128][129][130]133,134,161,…”