Encapsulating metal organic framework into hollow mesoporous carbon sphere as efficient oxygen bifunctional electrocatalyst

Abstract

Applying metal organic frameworks (MOFs) in electrochemical systems is a currently emerging field owing to the rich metal nodes and highly specific surface area of MOFs. However, the problems for MOFs that need to be solved urgently are poor electrical conductivity and low ion transport. Here we present a facile in situ growth method for the rational synthesis of MOFs@hollow mesoporous carbon spheres (HMCS) yolk–shell-structured hybrid material for the first time. The size of the encapsulated Zeolitic Imidazolate Framework-67 (ZIF-67) is well controlled to 100 nm due to the spatial confinement effect of HMCS, and the electrical conductivity of ZIF-67 is also increased significantly. The ZIF@HMCS-25% hybrid material obtained exhibits a highly efficient oxygen reduction reaction activity with 0.823 V (vs. reversible hydrogen electrode) half-wave potential and an even higher kinetic current density (JK = 13.8 mA cm−2) than commercial Pt/C. ZIF@HMCS-25% also displays excellent oxygen evolution reaction performance and the overpotential of ZIF@HMCS-25% at 10 mA cm−2 is 407 mV. In addition, ZIF@HMCS-25% is further employed as an air electrode for a rechargeable Zn–air battery, exhibiting a high power density (120.2 mW cm−2 at 171.4 mA cm−2) and long-term charge/discharge stability (80 h at 5 mA cm−2). This MOFs@HMCS yolk–shell design provides a versatile method for the application of MOFs as electrocatalysts directly.

Conductive Two‐Dimensional Phthalocyanine‐based Metal–Organic Framework Nanosheets for Efficient Electroreduction of CO2

“…Loading electroactive metal complexes into porous conductive substrates is a promising approach to reduce CO 2 with high current density because of their fast electron transfer capacity and accessible active sites. Compared with other substrates, crystalline porous metal–organic frameworks (MOFs) with designable metal clusters and functional organic linkers have shown high selectivity in electrocatalytic CO 2 RR and other electrocatalytic reaction due to their single active sites and large CO 2 adsorption uptake [35–51] . However, the poor electrical conductivity feature of the traditionally insulating MOFs usually results in low current density in CO 2 RR.…”

Conductive phthalocyanine-based metal-organic framework as a highly efficient electrocatalyst for carbon dioxide reduction reaction

“…Porous crystalline metal-organic frameworks (MOFs) with periodically arranged metal ions/clusters and organic ligands are considered to be promising candidates for CO 2 RR as their high surface areas, large CO 2 adsorption uptakes, and high density of tunable active single-sites [16][17][18][19][20][21]. However, most of the conventional MOFs constructed by carboxylatebased linkages are electrical insulators, which usually exhibit low current density [22][23][24][25]. Recent progress in successful synthesis of electrically conductive two-dimensional (2D) MOFs [26][27][28] has endowed them with highly efficient electrocatlytic performance in CO 2 RR.…”

Conductive Two‐Dimensional Phthalocyanine‐based Metal–Organic Framework Nanosheets for Efficient Electroreduction of CO2

“…Loading electroactive metal complexes into porous conductive substrates is apromising approach to reduce CO 2 with high current density because of their fast electron transfer capacity and accessible active sites.C ompared with other substrates,crystalline porous metal-organic frameworks (MOFs) with designable metal clusters and functional organic linkers have shown high selectivity in electrocatalytic CO 2 RR and other electrocatalytic reaction due to their single active sites and large CO 2 adsorption uptake. [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] However,the poor electrical conductivity feature of the traditionally insulating MOFs usually results in low current density in CO 2 RR. Hence,d eveloping conductive MOFs (CMOFs) with highly single-active sites for the CO 2 RR is extremely desirable.…”