Oxygen‐Rich Cobalt–Nitrogen–Carbon Porous Nanosheets for Bifunctional Oxygen Electrocatalysis

Abstract

Metal-nitrogen-carbon (M-N-C) materials have attracted much interest in bifunctional oxygen-involving electrocatalysis for rechargeable Zn-air batteries. Such M-N-C electrocatalysts with M-N x sites show good activity for the oxygen reduction reaction (ORR) but moderate activity for the oxygen evolution reaction (OER). Herein, an oxygen-rich M-N-C material (O-Co-N/C) with a highly porous nanosheet structure is reported as a bifunctional oxygen electrocatalyst, which is prepared by the direct pyrolysis of ultrathin CoO nanosheets decorated with zeolitic imidazolate framework-8 nanoparticles under an inert atmosphere. Particularly, Co nanoparticles in the O-Co-N/C electrocatalyst contain both Co-N x and Co-O x coordination environments to provide intrinsic active sites for the ORR and OER, respectively. Furthermore, electrochemical studies show that the O-Co-N/C catalyst retains comparable ORR activity to common M-N-C materials with a half-wave potential of 0.85 V vs the reversible hydrogen electrode and better OER activity with an overpotential of 0.29 V at the current density of 10 mA cm −2 . This study provides insights into the development of effective oxygen-involving electrocatalysts with bifunctional metal active centers coordinated by both nitrogen and oxygen atoms.

Robust Electronic Correlation of Co‐CoN4 Hybrid Active Sites for Durable Rechargeable Zn‐Air Batteries

“…[41] The existence of CN bonds is favorable for the adsorption of oxygen-containing intermediates on the surface of the Co-CoN 4 @NCNs catalyst. [42] The highresolution Co 2p spectrum of Co-CoN 4 @NCNs (Figure 3d) presents four cobalt-bearing components, including Co 0 (780.1 and 795.4 eV), [43] Co 2+ (783.4 and 798.1 eV), [44] CoN (781.4 and 796.7 eV), [45] and a shake-up satellite (786.8 and 802.5 eV). [46] Notably, the peak corresponding to Co 0 was smaller than that of Co 2+ because small Co clusters are prone to surface oxidation, resulting in the presence of CoO species on the catalyst surface.…”

Aerophilic Triphase Interface Tuned by Carbon Dots Driving Durable and Flexible Rechargeable Zn-Air Batteries

“…However, many transition metal catalysts have poor electrical conductivity and chemical durability, which seriously hinder their catalytic performance. It has been widely reported that the coupling between carbon materials and transition metal catalysts exhibits admirable activity and durability [ 22 , 23 ]. In particular, the inevitable agglomeration of transition metal catalysts during high-temperature sintering can be effectively restrained through the confinement of carbon supports.…”

Seeding Layer Approach for the Synthesis of Co-ZIF-90 Thin Films of Optical Quality

“…20−23 Still hampering the further translation into real-world applications is the fact that for many practical applications, the MOF has to be shaped into a specific morphology, like monoliths (pellets, tablets, and granules), gels or foams, membranes, or thin films as well as composite materials (e.g., on fibers or nanosheets). 24,25 For the deposition of MOF membranes and thin films, different supports like fibers, 26−28 porous disks, 29,30 nanosheets, 31,32 and flat surfaces (e.g., glass, silicon, and gold surfaces) 33−35 coordination of the metal ions in ZIFs and similar bond angles of Si−O−Si linkages in zeolites and N−[M]−N linkages in ZIFs, the structures of ZIFs possess strong structural similarities with zeolites. In most cases, Zn 2+ ions function as metal ions in ZIFs; however, ZIFs containing other metal ions like Co 2+ , Cu 2+ , and Cd 2+ are also known.…”

“…The linker molecules have at least two functional groups, which are used to connect the IBUs. Most MOFs possess linkers with carboxylate as coordinating functional group, − but other functional groups like amines can also be used for the coordination of the IBUs. , As a porous material, MOFs have high inner surface areas of up to a few thousand m 2 /g, enabling a variety of applications, like gas storage − and gas separation, − sensing, , and catalysis. , Furthermore, MOFs gain increasing interest in nonclassical application fields like biomedical technology − as well as electronics, optics and optoelectronics. − Still hampering the further translation into real-world applications is the fact that for many practical applications, the MOF has to be shaped into a specific morphology, like monoliths (pellets, tablets, and granules), gels or foams, membranes, or thin films as well as composite materials (e.g., on fibers or nanosheets). , For the deposition of MOF membranes and thin films, different supports like fibers, − porous disks, , nanosheets, , and flat surfaces (e.g., glass, silicon, and gold surfaces) − can be used.…”