Electric Field Redistribution Triggered Surface Adsorption and Mass Transfer to Boost Electrocatalytic Glycerol Upgrading Coupled with Hydrogen Evolution

Abstract

Electrocatalytic glycerol oxidation reaction (GOR) stands out as an economical and prospective technology to replace oxygen evolution reaction for co‐producing high‐valued chemicals and hydrogen (H2). Regulating the adsorption of glycerol (GLY) and hydroxyl (OH) species is of great significance for improving the GOR performance. Herein, a hierarchical p–n heterojunction by combining Co‐metal organic framework (MOF) nanosheets with CuO nanorod arrays (CuO@Co‐MOF) is developed to realize the optimization on GOR. Specifically, CuO@Co‐MOF electrode exhibits superior performance with a conversion of 98.4%, formic acid (FA) selectivity of 87.3%, and Faradaic efficiency (FE) of 98.9%. The flow‐cell system with the bifunctional CuO@Co‐MOF electrode for pairing GOR with the hydrogen evolution reaction (HER) reveals better energy conversion efficiency. Experimental results and theoretical calculations unravel the redistributed electric field by introducing Co‐containing species that contribute to the improved performance, which not only enhances the OH adsorption but also modulates the excessive GLY adsorption of CuO, thus reducing reaction energy barriers of FA desorption. Simultaneously, finite element analysis reveals that the novelty hierarchical structure can increase the concentration of OH− and facilitate the mass transfer of OH− in the solution.

Metal–organic frameworks (MOFs) for hybrid water electrolysis: structure–property–performance correlation

“…Upon increasing the potential from 1.03 to 1.63 V vs. RHE, the intensity of the characteristic peak associated with Co 2+ gradually diminished, while the band corresponding to CoOOH at 600 cm À1 intensified. 136 This observation confirmed the phase reconstruction from Co-MOF (Co 2+ ) to CoOOH (Co 3+ ), elucidating the transformation of the active catalyst structure during glycerol oxidation. 136 Song et al conducted an X-ray photoelectron spectroscopy (XPS) study to uncover the active catalyst structure of NiCo-61-MOF during benzyl alcohol oxidation.…”

“…136 This observation confirmed the phase reconstruction from Co-MOF (Co 2+ ) to CoOOH (Co 3+ ), elucidating the transformation of the active catalyst structure during glycerol oxidation. 136 Song et al conducted an X-ray photoelectron spectroscopy (XPS) study to uncover the active catalyst structure of NiCo-61-MOF during benzyl alcohol oxidation. 134 The XPS spectra of NiCo-61-MOF on nickel foam revealed that the Ni 2p 3/2 peak experienced a slight shift to a higher binding energy of 856.37 eV after benzyl alcohol oxidation, compared to the fresh electrocatalysts with a binding energy of 856.17 eV.…”

“…9a). 136 The formation of this heterostructure was confirmed through PXRD and TEM studies (Fig. 9b-d).…”

“…103 Likewise, in-situ Raman spectroscopy was employed to probe the active catalyst structure of CuO@Co-MOF during glycerol oxidation. 136 The insitu Raman spectra captured under various potentials in 1.0 M KOH with 0.1 M glycerol unveiled distinct signals at approximately B300, 510, and 600 cm À1 , corresponding to CuO, Co 2+ , and CoOOH, respectively. Upon increasing the potential from 1.03 to 1.63 V vs. RHE, the intensity of the characteristic peak associated with Co 2+ gradually diminished, while the band corresponding to CoOOH at 600 cm À1 intensified.…”

“…9g). 136 In a two-electrode system, CuO@Co-MOF exhibited a remarkable improvement of 0.47 V in cell voltage at a current density of 20 mA cm À2 for glycerol oxidation compared to the OER. 136 In another study, He et al developed Pt-loaded Fe-MIL for ethylene glycol oxidation, exhibiting an efficient mass activity of 11 826 mA mg pt…”