Cobalt Sulfide Nanoparticles Grown on Nitrogen and Sulfur Codoped Graphene Oxide: An Efficient Electrocatalyst for Oxygen Reduction and Evolution Reactions

Abstract

Electrochemical oxygen evolution and reduction reactions have received great attention due to their importance in several key technologies such as fuel cells, electrolyzers, and metal–air batteries. Here, we present a simple approach to the preparation of cobalt sulfide nanoparticles in situ grown on a nitrogen and sulfur codoped graphene oxide surface. The particle size and phase were controlled by changing the treatment temperature. Cobalt sulfide nanoparticles dispersed on graphene oxide hybrids were successfully prepared by a solid-state thermolysis approach at different temperatures (400, 500, and 600 °C) using cobalt thiourea and graphene oxide. X-ray diffraction studies revealed that hybrids prepared at 400 and 500 °C result in pure CoS2 phase, whereas the hybrid prepared at 600 °C exhibits Co9S8 phase. X-ray photoelectron spectroscopy studies revealed that nitrogen and sulfur simultaneously codoped on the graphene oxide surface, and these sites act to anchor the CoS2 nanoparticles strongly on the GO surface. The strong coupling between CoS2 and N,S-GO was reflected in the improvement of the oxygen electrode potential. CoS2(400)/N,S-GO showed an outstanding oxygen electrode activity with a potential of about 0.82 V against a reversible hydrogen electrode in alkaline medium, which is far better than the performance of precious catalysts such as Pt/C (1.16 V), Ru/C (1.01 V), and Ir/C (0.92 V).

Single‐Atom to Single‐Atom Grafting of Pt1 onto FeN4 Center: Pt1@FeNC Multifunctional Electrocatalyst with Significantly Enhanced Properties

“…[23,45] The other is associated with the low coordinated dangling Pt 4+ atoms that may facilitate the H 2 O adsorption and promote OER, although metallic Pt NPs are not active to OER. [22,46] In addition, the overvoltage (ΔE = E j = 10 −E 1/2 ) between OER and ORR, which is used to evaluate the reversibility of oxygen electrodes, is 0.67 V for Pt 1 @FeNC, much lower than that of the recently reported highly active NPMCs, precious metal, and metal-free catalysts, e.g., Co@Co 3 O 4 / NC (0.85 V), [47] Fe@N-C-700 (0.88 V), [48] 20 wt% PtRu/C (0.88 V), [49] S-doped CNTs (0.79 V). [50] The superior ORR/OER bifunction of Pt 1 @FeNC raises its potential application in regenerative fuel cell, which combine the fuel cell and water splitting in one device.…”

Design of Efficient Bifunctional Oxygen Reduction/Evolution Electrocatalyst: Recent Advances and Perspectives

“…[60][61][62][63] For example, Sun et al first found that layered double hydroxides (LDHs) can be used as bifunctional oxygen electrocatalysts. [60] NiCoFe-LDH shows a modest bifunctional ORR/OER activities.…”

Cobalt sulfide/N,S codoped porous carbon core–shell nanocomposites as superior bifunctional electrocatalysts for oxygen reduction and evolution reactions

“…Particularly, cobalt sulfides (Co x S y ) with different phases have been previously investigated as ORR and OER electrode catalysts and exhibited attractive electrocatalytic performance among different nonprecious and late transition metal chalcogenides. [18][19][20][21][22][23] For instance, CoS 2 is a good electrocatalyst for ORR and OER; 24 Co 3 S 4 has excellent performance for ORR 25,26 and OER; 26 while…”