The electrochemical interconversion of small molecules containing C, O, N, and H is at the core of energy chemistry. Research in the McCrory Lab generally focuses on using careful electroanalytical studies to elucidate the mechanism of electrocatalytic systems, then using this mechanistic understanding to inform the rational design of next-generation catalyst materials. We are broadly interested in the electrochemical interconversion of small molecules relevant to energy chemistry and upcycling wastes to new high-value chemicals and fuels.
In the McCrory group, our general research approach is to develop enabling technologies that allow for the careful study and control of electrocatalytic processes with an emphasis on kinetic and mechanistic analysis, and to use these approaches to address fundamental challenges in the electrochemical conversion of small molecules by solid-state and molecular catalysts. We use a combination of surface science and electrochemistry to directly observe reactive intermediates in the catalytic pathway in model systems and then use these mechanistic findings to develop new, efficient electrocatalytic materials. A few key projects in our group are discussed below.
Controlling Coordination Environment through Polymer Encapsulation
Encapsulating molecular electrocatalysts within coordinating polymers allows us to control the catalysts’ chemical microenvironments and promote higher activity and selectivity for electrochemical conversions. This approach is inspired by biological systems where fast catalytic activity and high reaction selectivity are achieved in enzymes through optimization of the primary, secondary, and outer coordination spheres of the enzymes’ active sites.
In particular, we have shown that immobilizing cobalt phthalocyanine (CoPc) inside of poly-4-vinylpyridine (P4VP) polymer films results in suppression of the competitive hydrogen evolution reaction and promotes the low overpotential reduction of CO2 to CO. The encapsulating polymer alters the catalyst’s primary, secondary, and outer coordination spheres synergistically to promote increased activity and selectivity for CO2 reduction. Our work focuses on understanding the fundamental mechanisms and kinetics of charge and substrate transport in these systems, and how this influences overall reaction activity and selectivity.
Our recent work in this area focuses on translating these polymer-catalyst composite systems from traditional aqueous-fed batch reactors to gas-fed flow electrolyzers to understand which microenvironment effects influence catalytic activity at larger scales.
Five Recent Manuscripts in this Research Area:
Mitigating Cobalt Phthalocyanine Aggregation in Electrocatalyst Films through Codeposition with an Axially Coordinating Polymer. Dean, W. S.; Soucy, T. L.; Rivera-Cruz, K. E.; Filien; L. L; Terry, B. D.; McCrory, C. C. L. Small, 2024, 2402293.
Electrochemical CO2 Reduction to Methanol by Cobalt Phthalocyanine: Quantifying CO2 and CO Binding Strengths and Their Influence on Methanol Production. Yao, L.†; Rivera Cruz, K. E.†, Zimmerman, P. M.; Singh, N.; McCrory, C. C. L. ACS Catalysis, 2024, 14, 366-372.
Challenges and Opportunities in Translating Immobilized Molecular Catalysts for Electrochemical CO2 Reduction from Aqueous-Phase Batch Cells to Gas-Fed Flow Electrolyzers. Yao, L.; Rivera Cruz, K. E.; Singh, N.; McCrory, C. C. L. Current Opinions in Electrochemistry, 2023, 101362.
The Influence of pH and Electrolyte Concentration on Fractional Protonation and CO2 Reduction Activity in Polymer-Encapsulated Cobalt Phthalocyanine. Soucy, T. L.; Dean, W. S.; Rivera Cruz, K. E.; Eisenberg, J. B.; McCrory, C. C. L. Journal of Physical Chemistry C, 2023, 127, 14041-14052.
Translating Catalyst-Polymer Composites from Liquid to Gas-Fed CO2 Electrolysis: A CoPc-P4VP Case Study. Yao, L., Yin, C.; Rivera Cruz, K. E.; McCrory, C. C. L.; Singh, N. R. ACS Applied Materials & Interfaces, 2023, 15, 31438-31448.
Molecular Electrocatalysis: Discrete Catalysts to Multidimensional Architectures
For most molecular electrocatalysts, introducing ligand modifications that shift the catalysts’ redox potentials more positive leads to a decrease in the metal site nucleophilicity, and in turn decreases the catalysts’ ability to coordinate and reduce CO2. This correlation between a catalyst’s redox potential, which governs catalytic onset, and nucleophilicity of the catalyst’s metal site leads to typical molecular scaling relationships: beneficial decreases in effective overpotential, the extra energy beyond the thermodynamic requirement needed to drive the reaction, are typically correlated with detrimental decreases in catalytic activity. Our work focuses on developing systems that break molecular scaling relationships that allow for the simultaneous minimization of overpotential and maximization of catalytic activity. Our approach is to design complexes with redox-active ligands where catalytic onset immediately follows ligand reduction, thus partially decoupling catalytic onset and effective overpotential from the nucleophilicity of the metal sites. We are also focused on incorporating molecular catalyst systems into macromolecular structures and understanding how this changes the kinetics and mechanisms of electrocatalytic transformations.
Five Recent Manuscripts in this Research Area:
Co-Co and Co-Zn Bimetallic Complexes for Electrocatalytic CO2 Reduction: The Role of Interrelated Intramolecular Effects on Activity. Zhou, J. K.†; Nie, W.-X.†; Tarnopol, D. E.; McCrory, C. C. L. Chem Catalysis, 2024, 4, 101006.
Strategies for Breaking Molecular Scaling Relationships for the Electrochemical CO2 Reduction Reaction. Nie, W.-X.*, McCrory, C. C. L. Dalton Transactions, 2022, 51, 6993-7010.
Enhancing a Molecular Electrocatalyst’s Activity for CO2 Reduction by Simultaneously Modulating Three Substituent Effects. Nie, W.-X.; Tarnopol, D. E.; McCrory, C. C. L. Journal of the American Chemical Society, 2021, 143, 3764-3778.
The Effect of Extended Conjugation on Electrocatalytic CO2 Reduction by Molecular Catalysts and Macromolecular Structures. Nie, W.-X.; Tarnopol, D. E.; McCrory, C. C. L. Current Opinions in Electrochemistry, 2021, 28, 100716.
Controlled Growth of Multilayer Films of Discrete Molecular Catalysts using a Layer-by-Layer Growth Mechanism Based on Sequential Click Chemistry. Kallick, J. K.; Feng, W.-J.; McCrory, C. C. L. “” ACS Applied Energy Materials,2020, 3,6222-6231.
Role of Metal Dopants in Heterogeneous Electrocatalysts
Our group is interested in understanding the role of dopants, both intentional and unintentional, on electrocatalytic activity and product distributions for the oxygen evolution reaction (OER) and the CO2 reduction reaction (CO2RR). Much of our work has focused on designing new Co3-xMxO4 spinel materials for the OER, where M is an early transition metal. In particular, we have explored how the incorporation of different metals into the lattice influences catalytic activity and stability for the OER. Moving forward, we are focused on expanding this work to understand how changing the composition and structure of Co3-xMxO4 spinel materials influence activity for other oxidative reactions such as selective alcohol oxidation.
Our other efforts have focused on quantifying the influence of trace-metal contaminants such as Ag+ from reference electrodes on CO2RR product distributions at Cu electrodes.
Four Recent Manuscripts in this Research Area:
Electrochemical Oxidation of Primary Alcohols using a Co2NiO4 Catalyst: Effects of Alcohol Identity and Electrochemical Bias on Product Distribution
Michaud, S. E.; Barber, M. M.; Rivera-Cruz, K. E.; McCrory, C. C. L. ACS Catal., 2023, 13, 515-529.
A CoV2O4 Precatalyst for the Oxygen Evolution Reaction: Highlighting the Importance of Postmortem Catalyst Characterization in Electrocatalysis Studies.
Michaud, S. E.; Riehs, M. T.; Feng, W.-J.; Lin, C-C.; McCrory, C. C. L. Chem. Commun. 2021, 57, 883-886.
The Effect and Prevention of Trace Ag+ Contamination from Ag/AgCl Reference Electrodes on CO2 Reduction Product Distributions at Polycrystalline Copper Electrodes
Leung, K-Y.; McCrory, C. C. L. ACS Appl. Energy Mater., 2019, 2, 8283-8293.
Effect of Chromium Doping on Electrochemical Water Oxidation Activity by Co3-xCrxO4 Spinel
Lin, C-C.; McCrory, C. C. L. ACS Catal., 2017, 7, 443-451.