Shaping the energy landscape toward renewable, carbon-free energy resources is a contemporary challenge that will require significant advancements in the development of catalysts/electrocatalysts for energy and chemical conversion processes. The goal of our research group is to design active, selective and stable heterogeneous catalysts and electrocatalysts for these processes. Specifically, we focus on the development of heterogeneous catalysts and electrocatalysts for electrochemical conversion and storage (i.e. fuel cells, electrolyzers, batteries) and cooperative/selective thermal catalysis for biomass upgrading, plastics upcycling and mitigation of greenhouse gasses. As an integral part of engineering catalytic/electrocatalytic structures, we implement a paradigm which involves a combination of controlled synthesis, advanced characterization, kinetic measurements and quantum chemical calculations to unearth the underlying mechanism that governs their catalytic performance for targeted reactions.

Research Projects

Engineering complex layered metal oxides for oxygen electrocatalysis.

Oxygen electrocatalysis (ORR and OER) has attracted significant attention due to its critical role in the performance of important electrochemical energy conversion and storage devices, such as fuel cells, electrolyzers, and metal-air batteries. First-series Ruddlesden-Popper (R-P) oxides with a formula of A2BO4 have emerged as promising electrocatalysts for oxygen electrocatalysis due to their suitable mixed ionic and electronic conductivities. In this research project, we investigate the surface structure and composition as parameters to understand and tune the ORR/OER activity of these oxides. We utilize quantum chemical calculations combined with detailed characterization, controlled synthesis, and testing as effective ways for developing the fundamental knowledge at the molecular level required to guide the design of efficient nonstoichiometric, mixed metal oxides for oxygen electrocatalysis.

Engineering complex layered metal oxides for oxygen electrocatalysis
Free energy surface of the oxygen exchange process on (001), (100) and (111) La2NiO4 surfaces. (Inset) The mechanism for oxygen exchange on La2NiO4.
Current density versus voltage for H2 oxidation in a solid oxide fuel cell (SOFC) containing La2NiO4 nanorods and nanospheres, as well as the state-of-the-art La0.8Sr0.2MnO3.

Related and Selected Publications:

    ‡ These authors contributed equally to this work

Tuning solid-solid interfacial catalysis in alkali metal-air battery cathodes.

The development of high-energy density batteries that enable electrification of the transportation sector remains a challenge. Metal-air batteries, especially the Li-air technology, have attracted significant interest over the last two decades due to their comparable energy density to that of gasoline. However, these systems are limited by large overpotential losses, during the molecular oxygen electrocatalysis resulting in low voltaic efficiencies. Our approach involves a combination of quantum theoretical calculations, controlled synthesis, kinetic studies, and thorough characterization to study and tune catalysis at the solid-solid interfaces of the battery cathodes where solid discharge products are formed and dissociated on solid electrocatalyst surfaces. The objective is to lower the cell overpotential losses by tuning the discharge product distribution.

Related and Selected Publications:

Characterization of La2NiO4
Characterization of La2NiO4 nanorods & slow anodic sweep voltammograms (SASV) of carbon-only cathode with preloaded Li2O2 (black curve) and LNO/carbon cathode with preloaded Li2O2 (red curve).

H2O splitting and CO2 reduction using solid oxide electrolyzers.

The interest in developing solid oxide electrolysis cells (SOECs) for electrochemical reduction of CO2 and water is steadily increasing as an approach to convert surplus energy from intermittent energy sources into chemical energy, while also mitigating CO2 emissions. The key challenges with this technology include high overpotential losses associated with the electrochemical reactions (i.e. oxygen evolution reactions (OER) and CO2 and H2O co-reduction) at the SOEC electrodes. This project aims to (1) investigate the optimization of catalytic activity of SOEC fuel electrode through the use of layered nickelate oxides as promising electrocatalysts for OER, and (2) assess the activity and stability of metal/metal-alloy based electrodes under conventional SOEC working conditions as electrocatalyst for and CO2 and H2O co-reduction. Our approach involves a combination of DFT calculations and microkinetic modeling with controlled electrochemical experiments to understand the chemical/electrochemical processes that govern H2O and CO2 co-electrolysis with the aim of identifying optimal electrocatalysts for this process.

Related and Selected Publications:

      ‡ These authors contributed equally to this work

Optimal Electrocatalysts for High Temperature CO2 Electrolysis
Optimal Electrocatalysts for High Temperature H2O Electrolysis

Design of multifunctional catalyst for selective catalysis.

Metal-metal oxide catalysts have attracted significant attention in heterogeneous catalysis because of the interesting catalytic activity of the metal-metal oxide interface that can result in enhanced catalytic performance. In the project, our objective is to design “inverted” metal-metal oxide systems, in which metal oxide films are deposited on top of metallic substrates, in order to: (i) increase the density of metal-metal oxide interfacial sites; (ii) improve the chemical and thermal stability of small metal NPs by encapsulation; and (iii) provide spatially regulated delivery of reactants to the interfacial sites. One of the examples is the successful synthesis of encapsulated monodispersed Pd NPs in a porous TiO2 film with controllable pore size which leads to high selectivity toward hydrodeoxygenation of biomass-derived alcohols. (Zhang, J. *, Wang, B. *, Nikolla, E., & Medlin, J. W., Angewandte Chemie, 2017, 129, 6694) Catalyst selectivity was found to be a strong function of both the presence of Pd-TiO2 interfacial sites and the pore size of the TiO2 shell.

Related and Selected Publications:

  ‡ These authors contributed equally to this work

Characterization of Pd@TiO2 encapsulated structures
Orientation based Selective Catalysis: Controlled and selective binding as well as interfacial sites induced by nanoporous TiO2 film during the reaction of benzyl alcohol and furfuryl alcohol on Pd catalysts.

Funding Sources

us department of energy

Department of Energy – Office of Basic Energy Sciences
National Science Foundation
Toyota Motor North America, Inc
camille foundation

The Camille and Henry Dreyfus Foundation