Synthesis of metal-organic framework-derived cobalt disulfide with high-performance oxygen reduction reaction catalytic properties

Metal-organic framework (MOF)-derived plate-shaped CoS1.097 nanoparticles for an improved hydrogen evolution reaction

Metal-organic framework (MOF)-derived transition metal sulfides are viewed as reliable, cost-effective, and alternative hydrogen evolution reaction (HER)-efficient electrocatalysts. They have been used to replace platinum (and their alloys) for production of renewable energy carriers such as hydrogen. Progress towards development of non-precious transition-metal sulfides through different synthetic routes to obtain unique morphological nanostructures with enhanced HER activity is challenging. We introduced a transition-metal sulfide, cobalt sulfide (CoS_1.097), derived from a cobalt MOF [Co-BPY-DDE] by following facile, one-step solvothermal sulfurization. By varying the sulfurization temperature (from 140 °C to 180 °C) during the solvothermal method, three cobalt-sulfide products were obtained: CoS_1.097-140, CoS_1.097-160, and CoS_1.097-180, respectively. Temperature variation had a vital role in optimizing the HER activity of the electrocatalyst. Besides, notable plate-shaped cobalt sulfide nanoparticles (CoS_1.097-160) required overpotential of 163 mV to deliver a current density of 10 mA cm^-2 with a low Tafel slope of 53 mV dec^-1, thereby demonstrating faster reaction kinetics during the evolution of molecular hydrogen. Furthermore, 25 h of long-term stability of the electrocatalyst reflected its practical applicability in acidic media. CoS_1.097-160 had uniform plate-shaped morphology and large electrochemical active surface area, which contributed to enhanced electrochemical performance through water electrolysis.

Functionality and design of Co-MOFs: unique opportunities in electrocatalysts for oxygen reduction reaction

The first report highlighting miraculous and intelligent electrocatalysts that can be tailored to form useful structures and morphologies with active sites for the oxygen reduction reaction.

Rational Design of Hierarchical, Porous, Co-Supported, N-Doped Carbon Architectures as Electrocatalyst for Oxygen Reduction

Developing highly active nonprecious-metal catalysts for the oxygen reduction reaction (ORR) is of great significance for reducing the cost of fuel cells. 3D-ordered porous structures could substantially improve the performance of the catalysts because of their excellent mass-diffusion properties and high specific surface areas. Herein, ordered porous ZIF-67 was prepared by forced molding of a polystyrene template, and Co-supported, N-doped, 3D-ordered porous carbon (Co-NOPC) was obtained after further carbonization. Co-NOPC exhibited excellent performance for the ORR in an alkaline medium with a half-wave potential of 0.86 V vs. reversible hydrogen electrode (RHE), which is higher than that of the state-of-the-art Pt/C (0.85 V vs. RHE). Moreover, the substantially improved catalytic performance of Co-NOPC compared with Co-supported, N-doped carbon revealed the key role of its hierarchical porosity in boosting the ORR. Co-NOPC also exhibited a close-to-ideal four-electron transfer path, long-term durability, and resistance to methanol penetration, which make it promising for large-scale application.