In situ growth of ZIF67 at the edge of nanosheet transformed into yolk-shell CoSe2 for high efficiency urea electrolysis

Abstract

Metal–organic frameworks (MOFs) derivatives are excellent electrocatalytic materials due to their own structural characteristics. However, it is still very essential to design a logical synthesis route of MOFs derivatives to avoid the adverse effects caused by the collapse of MOFs structure and improve its intrinsic catalytic activity. For these reasons, we designed and synthesized cobalt-based metal-organic framework (ZIF67) grown in situ at the edge of Co(OH)2 nanosheets. Through adjusting the alcohol-water ratio of the reaction solution, the number of ZIF67 grown on the Co(OH)2 can be controlled to make it grow uniformly at the edge of nanosheet. After the selenization reaction in a tube furnace, ZIF67 is transformed into CoSe2 (Co-Z/Se-2) with a yolk-shell structure. This precisely designed synthetic route allows Co-Z/Se-2 to expose more active sites, which is conducive to electron transport and has good performance in both urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Co-Z/Se-2 as UOR catalyst only needs 1.390 V to reach 50 mA cm−2. Co-Z/Se-2 as bifunctional catalysts, are assembled to be a urea electrolyzer cell. Co-Z/Se-2 || Co-Z/Se-2 only needs 1.490 V to drive 10 mA cm−2, and can maintain a good stability for 20 h.