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01 Apr 13:13

Oriented Transformation of Co‐LDH into 2D/3D ZIF‐67 to Achieve Co–N–C Hybrids for Efficient Overall Water Splitting

by Ziliang Chen, Yuan Ha, Huaxian Jia, Xiaoxiao Yan, Mao Chen, Miao Liu, Renbing Wu
Advanced Energy Materials Oriented Transformation of Co‐LDH into 2D/3D ZIF‐67 to Achieve Co–N–C Hybrids for Efficient Overall Water Splitting

An easy‐manipulation pseudomorphic replication approach is employed to enable the synthesis of 2D ZIF‐67 nanosheets grafted with 3D ZIF‐67 polyhedral architecture on the surface of carbon cloth (CC). After a pyrolysis process, 2D/3D ZIF‐67@CC is converted into a self‐supporting electrocatalyst consisting of ultrafine cobalt nanoparticles embedded within N‐doped 2D/3D carbon framework, exhibiting an exceptional overall water‐splitting performance.


Abstract

Construction of well‐defined metal–organic framework precursor is vital to derive highly efficient transition metal–carbon‐based electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting. Herein, a novel strategy involving an in situ transformation of ultrathin cobalt layered double hydroxide into 2D cobalt zeolitic imidazolate framework (ZIF‐67) nanosheets grafted with 3D ZIF‐67 polyhedra supported on the surface of carbon cloth (2D/3D ZIF‐67@CC) precursor is proposed. After a low‐temperature pyrolysis, this precursor can be further converted into hybrid composites composed of ultrafine cobalt nanoparticles embedded within 2D N‐doped carbon nanosheets and 3D N‐doped hollow carbon polyhedra (Co@N‐CS/N‐HCP@CC). Experimental and density functional theory calculations results indicate that such composites have the advantages of a large number of accessible active sites, accelerated charge/mass transfer ability, the synergistic effect of components as well as an optimal water adsorption energy change. As a result, the obtained Co@N‐CS/N‐HCP@CC catalyst requires overpotentials of only 66 and 248 mV to reach a current density of 10 mA cm−2 for HER and OER in 1.0 m KOH, respectively. Remarkably, it enables an alkali‐electrolyzer with a current density of 10 mA cm−2 at a low cell voltage of 1.545 V, superior to that of the IrO2@CC||Pt/C@CC couple (1.592 V).