Confinement Catalyst of Co₉S₈@N-Doped Carbon Derived from Intercalated Co(OH)₂ Precursor and Enhanced Electrocatalytic Oxygen Reduction Performance

Abstract

Oxygen reduction reaction (ORR) is an important cathode reaction in fuel cells and metal–air batteries. Composites of transition-metal sulfides (TMSs) and nitrogen-doped carbon (NC) are promising alternative ORR catalysts because of their high catalytic activity. However, the agglomeration of TMS particles limits practical applications. Here, a confinement catalyst composed of Co9S8@NC with a flower-like morphology was derived from metanilic intercalated Co­(OH)2 through interlayer-confined carbonation accompanied with host-layer sulfidation. The surface of the Co9S8 particles is covered with a few layers of nitrogen-doped graphene, which can prevent the Co9S8 particles from agglomeration and also produce catalytic activity affected by internal Co9S8. Thus, the Co9S8@NC material achieves excellent ORR performance with a half-wave potential of 0.861 VRHE. In addition, an oxide layer on the surface of Co9S8@NC is fabricated shortly after the ORR starts. Further tests and density functional theory calculations indicated that this cobalt oxide layer can increase the electrochemically active area of Co9S8@NC as well as reduce the ORR energy barrier, thereby providing more catalytic active sites and enhancing the intrinsic catalytic activity, thus achieving a self-activation effect during the electrochemical reaction process.

Controlling the Co–S coordination environment in Co-doped WS2 nanosheets for electrochemical oxygen reduction

“…[19][20][21][22][23][24][25] The Co 9 S 8 phase, in particular, has been identi-ed as uniquely active amongst the rst-row transition metal suldes for alkaline and neutral ORR and has been studied in a wide range of composite nanostructures. [26][27][28][29][30][31][32][33] Computational studies have postulated that the M-S coordination environment at the catalytic surface inuences oxygen adsorbate binding energies and thus ORR catalytic turnover. 34,35 However, when experimentally altering the crystal structure or composition of a bulk metal sulde phase, it is challenging to isolate the role that coordination environment plays amidst the multiple geometries and oxidation states that exist within any given phase as well as the dynamic nature of the surface under electrocatalytic conditions.…”

Transition Metal (Fe, Ni, Mn) with Heteroatoms B and S Tri-doped Co/C Catalysts for Oxygen Reduction Reaction

“…It gives joint isotherm curves of II and IV hysteresis loops, revealing the presence of micropore and mesopore structures. , The Brunauer–Emmett–Teller (BET) specific surface area of FeBS-Co/C is 62.8 m 2 /g. Derived from its desorption branch, in Figure b, its Barrett–Joyner–Halenda (BJH) pore size distribution curve confirms the presence of mesopores with an average pore diameter and a pore volume of 10 nm and 0.2 cm 3 /g, respectively, conducive to the penetration of an electrolyte and the diffusion of a reactant (oxygen molecule) …”

“…Derived from its desorption branch, in Figure 3b, its Barrett− Joyner−Halenda (BJH) pore size distribution curve confirms the presence of mesopores with an average pore diameter and a pore volume of 10 nm and 0.2 cm 3 /g, respectively, conducive to the penetration of an electrolyte and the diffusion of a reactant (oxygen molecule). 26 Figure 4a−d shows the TEM and high-resolution TEM (HR-TEM) images of FeBS-Co/C with different sizes (100, 50, 20, and 10 nm). These images clearly show the amorphous carbon of FeBS-Co/C with nearly no agglomeration of metal particles, conducive to the transmission of electrons and reactants.…”

Cation Modulation of Cobalt Sulfide Supported by Mesopore-Rich Hydrangea-Like Carbon Nanoflower for Oxygen Electrocatalysis

“…A robust and efficient oxygen electrocatalyst should satisfy multiple criteria including high intrinsic activity, abundant active site, large ion-accessible surface area, good electronic conductivity, and excellent chemical and structural stabilities. Transition-metal sulfides (TMSs) have multiple 3d electron configurations and can in situ evolve into highly efficient (oxy)­hydroxides via anionic leaching induced surface reconstruction process − and thus are considered a promising alternative to PGM catalysts. However, a sole component is still insufficient for simultaneously catalyzing the sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) due to the nonoptimized electronic structure and low active site number.…”