Green Energy & Environment (Apr 2024)
Engineering hierarchical quaternary superstructure of an integrated MOF-derived electrode for boosting urea electrooxidation assisted water electrolysis
Abstract
Controllable design of the catalytic electrodes with hierarchical superstructures is expected to improve their electrochemical performance. Herein, a self-supported integrated electrode (NiCo-ZLDH/NF) with a unique hierarchical quaternary superstructure was fabricated through a self-sacrificing template strategy from the metal–organic framework (Co-ZIF-67) nanoplate arrays, which features an intriguing well-defined hierarchy when taking the unit cells of the NiCo-based layered double hydroxide (NiCo-LDH) as the primary structure, the ultrathin LDH nanoneedles as the secondary structure, the mesoscale hollow plates of the LDH nanoneedle arrays as the tertiary structure, and the macroscale three-dimensional frames of the plate arrays as the quaternary structure. Notably, the distinctive structure of NiCo-ZLDH/NF can not only accelerate both mass and charge transfer, but also expose plentiful accessible active sites with high intrinsic activity, endowing it with an excellent electrochemical performance for urea oxidation reaction (UOR). Specially, it only required the low potentials of 1.335, 1.368 and 1.388 V to deliver the current densities of 10, 100 and 200 mA cm−2, respectively, much superior to those for typical NiCo-LDH. Employing NiCo-ZLDH/NF as the bifunctional electrode for both anodic UOR and cathodic HER, an energy-saving electrolysis system was further explored which can greatly reduce the needed voltage of 213 mV to deliver the current density of 100 mA cm−2, as compared to the conventional water electrolysis system composed of OER. This work manifests that it is prospective to explore the hierarchically nanostructured electrodes and the innovative electrolytic technologies for high-efficiency electrocatalysis.
