Metal-organic-frameworks passivated CuBi2O4 photocathodes boost CO2 reduction kinetics
Jiaqi Jin, Guangming Cao, Yanjie Liu, Yingying Shu, Zhiyuan Deng, Wei Sun, Xiaogang Yang
Abstract
Photoelectrochemical reduction of CO2 to produce CO with metal-organic frameworks (MOFs) is recognized as a desirable technology to mitigate CO2 emission and generate sustainable energy. To achieve highly efficient electrocatalyst, it is essential to design a new material interface and uncover new reaction mechanisms or kinetics. Herein, we developed two metal-organic Cu-MOF and Bi-MOF layers using benzene tricarboxylic acid (H3BTC) ligands on CuBi2O4 photocathodes. Both MOF layers drastically improved the photoelectrochemical stability by suppressing the photo-corrosion through conformal surface passivation. The Cu-MOF modified CuBi2O4 showed more significant charge separation and transfer efficiencies than the Bi-MOF modified control. Based on the transient photocurrent curves under the applied potential of 0.6 V vs. RHE, the rate-law analysis showed the CO2 photoreduction took place through a first-order reaction. Further, the photoelectrochemical impedance spectra (PEIS) revealed this reaction order, representing an “operando” analysis. Moreover, the reaction rate constant on Cu-MOF modified sample was higher than that on Bi-MOF modified one and bare CuBi2O4. Combined with the density functional theory calculation, the surface absorption of CO2 and CO molecules and the higher energy barrier for *COOH intermediates could significantly determine the first order reaction.