Fe₃O₄‐Decorated Co₉S₈ Nanoparticles In Situ Grown on Reduced Graphene Oxide: A New and Efficient Electrocatalyst for Oxygen Evolution Reaction

Abstract

Cobalt sulfide materials have attracted enormous interest as low‐cost alternatives to noble‐metal catalysts capable of catalyzing both oxygen reduction and oxygen evolution reactions. Although recent advances have been achieved in the development of various cobalt sulfide composites to expedite their oxygen reduction reaction properties, to improve their poor oxygen evolution reaction (OER) activity is still challenging, which significantly limits their utilization. Here, the synthesis of Fe3O4‐decorated Co9S8 nanoparticles in situ grown on a reduced graphene oxide surface (Fe3O4@Co9S8/rGO) and the use of it as a remarkably active and stable OER catalyst are first reported. Loading of Fe3O4 on cobalt sulfide induces the formation of pure phase Co9S8 and highly improves the catalytic activity for OER. The composite exhibits superior OER performance with a small overpotential of 0.34 V at the current density of 10 mA cm−2 and high stability. It is believed that the electron transfer trend from Fe species to Co9S8 promotes the breaking of the Co–O bond in the stable configuration (Co–O–O superoxo group), attributing to the excellent catalytic activity. This development offers a new and effective cobalt sulfide‐based oxygen evolution electrocatalysts to replace the expensive commercial catalysts such as RuO2 or IrO2.

Reduced Graphene Oxide‐Wrapped Co9–xFexS8/Co,Fe‐N‐C Composite as Bifunctional Electrocatalyst for Oxygen Reduction and Evolution

“…Also, the successful incorporation of Fe to Co 9 S 8 and CoNC may further optimize their surface structures due to the synergistic electronic interaction. A similar electron transformation from Fe to Co was reported previously by Shen and co‐workers, the Fe species is electron deficient and serves as Lewis acid, thus providing a higher alkaline environment (Lewis base) around Co 9 S 8 , which is beneficial for the oxygen evolution with a higher concentration of OH − . The active CoFeS species in the surface may first transform to Fe decorated CoO x /CoOOH during OER process.…”

“…Co 2p 3/2 spectrum of S‐Co 9– x Fe x S 8 @rGO‐10 is deconvoluted into three peaks, corresponding to Co 0 , Co 2+ /Co 3+ , and satellite peaks Co sat at 778.7, 780.2, and 782.8 eV, respectively. As for S‐Co 9 S 8 @rGO, obvious positive shift of Co 0 peak was observed in comparison to S‐Co 9– x Fe x S 8 @rGO‐10, as shown in Figure S10d (Supporting Information), indicating the electron transfer from Fe to Co after Fe doping . The specific surface area and corresponding pore size distribution of both S‐Co 9 S 8 @rGO and S‐Co 9– x Fe x S 8 @rGO‐10 have also been tested.…”

Preparation of Yolk–Shell‐Structured CoxFe1−xP with Enhanced OER Performance

“…[23] In Figure 4A,t he overpotentials of Co x Fe 1Àx Pc atalysts at 10 mA cm À2 are 297 (Co 0.24 Fe 0.76 P), 277 (Co 0.47 Fe 0.53 P), and 288 mV (Co 0.63 Fe 0.37 P), which are much smaller than those of CoP (340 mV), FeP (480 mV), CoFeP-S( 310 mV), commercialI rO 2 (364 mV), and cobalt ferrite-2( 458 mV). Linears weep voltammetry (LSV) curveso fv ariousc atalysts are shown in Figure 4A.Compared with cobalt ferrite, CoP,FeP,and commercial IrO 2 ,C o x Fe 1Àx Pm icrospheres show significantly superior performance, which is characterizedb yalower overpotential.…”

Vertically Aligned Porous Nickel(II) Hydroxide Nanosheets Supported on Carbon Paper with Long‐Term Oxygen Evolution Performance

“…[1][2][3] The OER is at hermodynamically andk inetically demanding process, because it involves four sequential proton-coupled electron-transfer steps and the formation of oxygen-oxygen bonding. In this context, considerable research efforts have recently been de-voted to the search for efficient and inexpensive OER catalysts comprising earth-abundant elements, including transitionmetal oxides, [8][9][10] hydroxides, [11][12][13] perovskites, [14,15] phosphates, [16,17] sulfides, [18,19] and recently reported phosphides. [4] Presently,r uthenium and iridium oxides( RuO 2 and IrO 2 )a re state-of-the-artO ER catalysts [5][6][7] and are particularly indispensable for water electrolysis in acidic solution.H owever, both Ru and Ir are expensive and have limited availability in the earth'sc rust, and therefore, it is not practical to deploy electrochemical devices containing RuO 2 or IrO 2 catalysts on av ery large scale commensurate with globald emand.…”