A MOF‐Based Spatial‐Separation Layer to Enable a Uniform Favorable Microenvironment for Electrochemical CO<sub>2</sub> Reduction
Xu Han, Ting Zhang, Martí Biset‐Peiró, Siqi Zhao, Sebastián Murcia‐López, Kim Daasbjerg, J.R. Morante, Jian Li, Jordi Arbiol
Abstract
Regulating the local microenvironment of active sites to increase their specific CO 2 concentration and pH gradient, is a promising approach to optimize the electrochemical CO 2 reduction reaction (eCO 2 RR). However, currently reported morphological strategies display an uncertainty to the compatibility and distribution between catalytic sites and their microenvironment. Here, a uniform spatial‐separation metal–organic framework (MOF) layer between active sites and bulk electrolyte is proposed, which enables each active site to locate in a similarly favorable microenvironment. Zinc oxide (ZnO) nanorods (NR), a representative electrocatalyst for eCO 2 RR, is covered with a Zeolitic imidazolate framework‐8 (ZIF‐8) thin layer to serve as a model system. The prepared ZnO NR@ZIF‐8 exhibits an enhanced Faradaic efficiency toward CO at a wide range of potentials and reaches a maximum FE of CO (85%) at −1.05 V versus reversible hydrogen electrode, which is one of the best records till date. Moreover, the hydrophobic ZIF‐8 layer protects ZnO against self‐reduction. Such performance benefits from the porous ZIF‐8 shell with high CO 2 affinity, realizing efficient CO 2 access and retaining an increased local pH near ZnO active sites.