Probing the Synergistic Effects of Mg²⁺ on CO₂ Reduction Reaction on CoPc by In Situ Electrochemical Scanning Tunneling Microscopy

Abstract

We report herein the in situ electrochemical scanning tunneling microscopy (ECSTM) study on the synergistic effect of Mg 2+ in CO 2 reduction reaction (CO 2 RR) catalyzed by cobalt phthalocyanine (CoPc). ECSTM measurement molecularly resolves the self-assembled CoPc monolayer on the Au(111) substrate. In the CO 2 environment, high-contrast species are observed in the adlayer and assigned to the CO 2 adsorption on CoPc. Furthermore, the contrast of the CO 2 -bound complex is higher in Mg 2+ -containing electrolytes than in Mg 2+ -free electrolytes, indicating the formation of the CoPc-CO 2 -Mg 2+ complex. The surface coverage of adsorbed CO 2 is positively correlated with the Mg 2+ concentration as the additive in electrolytes up to a plateau of 30.8 ± 2.7% when c(Mg 2+ ) > 30 mM. The potential step experiment indicates the higher CO 2 adsorption dynamics in Mg 2+ -containing electrolytes than without Mg 2+ . The rate constants of CO 2 adsorption and dissociation in different electrolytes are extracted from the data fitting of statistical results from in situ ECSTM experiments.

Improving the Stability, Selectivity, and Cell Voltage of a Bipolar Membrane Zero‐Gap Electrolyzer for Low‐Loss CO2 Reduction

“…Here we also find evidence for K + crossover to the cathode from the anolyte (Figure S8, Supporting Information). The cation effect is less studied on molecular catalysts, but there are reports on selectivity enhancement over CoPc [30] and Fe porphyrins, [31] mainly attributed to stabilization of the M-CO 2 adduct (M is the transition metal center). Whilst this paper was in preparation a preliminary report of K + stabilization of CO 2 binding at a similar Co catalyst has also been reported supporting that a cation effect may also be occurring here.…”

Single-Molecule Study on the Catalytic Role of Co–O2 Binding in ORR by In Situ ECSTM

“…Electrochemical scanning tunneling microscopy (ECSTM) operates in the electrochemical environments and is capable of imaging the sample surface at subnanometric resolution under real electrochemical reaction conditions. − Specifically, ECSTM allows the structural characterization of model catalytic systems such as MPs and MPcs on the electrode surface. − Furthermore, by controlling the sample potential using a four-electrode bipotentiostat system, ECSTM enables the in situ probing of catalysis-related surface electrochemical processes including adsorption, diffusion, and transformation. − For example, the molecular structure and catalytic conversion of FePc during ORR can be monitored in situ by using ECSTM . In the electrocatalytic production of H 2 O 2 , the CoTMPP–OOH – complex is distinguished in the CoTMPP adlayer by the contrast in ECSTM images .…”

Oxygen-Bridged Long-Range Dual Sites Boost Ethanol Electrooxidation by Facilitating C–C Bond Cleavage

“…Previous reports document that a single metal site is insufficient to promote the multilevel electrocatalytic reaction by inducing the local electron difference. − Notably, the interatomic electronegativity offset for adjacent sites is a crucial factor for ensuring the occurrence of multisite catalytic reactions, where there is a relatively strong redox potential across the nearby atoms. , Thus, constructing efficient dual sites is promising for facilitating the alcohol oxidation reactions . For example, implanting the isolated metal species onto the Pt surface to construct dual sites is greatly developed in recent years, − which can modify the electronic structure of Pt sites to some extent, − thus favoring small organic molecule catalysis. − Some theoretical reports predict that Rh–Pt dual sites can steer C–C bond breaking due to the strain and ligand effects .…”

“…20,21 Thus, constructing efficient dual sites is promising for facilitating the alcohol oxidation reactions. 22 For example, implanting the isolated metal species onto the Pt surface to construct dual sites is greatly developed in recent years, 23−31 which can modify the electronic structure of Pt sites to some extent, 32−34 thus favoring small organic molecule catalysis. 35−40 Some theoretical reports predict that Rh−Pt dual sites can steer C−C bond breaking due to the strain and ligand effects.…”