image: Electrochemical performance of Co X-ides toward ECHQ: (a) LSV curves at scan rate of 10 mV s−1 in the electrolyte of 12 mL 1.0 M KOH and 2 mL of dioxane mixture solution (with and without 0.2 mmol of 1a); (b-c) GC‒MS results; (d) 1H NMR and (e) 13C NMR comparison of the product of Co3O4F, standard 1a and standard 2a; (f) Conversion and selectivity of Co3O4 under different bias potential; (g) Time-dependent evolution of 1a and its product 2a over Co3O4; (h) Conversion and selectivity comparison of Co X-ides; (i) Cycle-dependent performance of transforming 1a into 2a over Co3O4. Error bars correspond to the standard deviation of three independent measurements.
Credit: ©Hao Li et al.
The unsung heroes of electrochemical reactions - electrocatalysts - can assist in optimizing factors such as the reaction's speed, yield, and energy consumption. As such, these electrocatalysts are crucial for optimizing large-scale production in pharmaceutical, agrochemical, and petrochemical industries. Researchers at Tohoku University and Nanjing Normal University conducted a deep dive on the performance of an emerging category of electrocatalysts: cobalt oxides (henceforth referred to as Co X-ides).
The research team sought to use Co X-ides for the electrocatalytic hydrogenation of quinoline (ECHQ). This process is an attractive alternative to other methods, as it can be conducted under ambient temperatures and can result in a net zero carbon footprint. In comparison, conventional methods to hydrogenate quinoline release undesirable byproducts, and require the storage and transportation of highly flammable hydrogen - which is equal parts dangerous and costly.
"Previous research on ECHQ focused more on the optimization of catalytic activity, whereas for ECHQ reaction mechanisms and reaction path explorations, we might as well be starting with a blank page," explains Tianyi Wang from Tohoku University's Advanced Institute for Materials Research (WPI-AIMR).
"One goal of this study was to try and find which Co X-ide was "the best" one," says Hao Li of WPI-AIMR, "However, we also need to be able to understand why certain catalysts perform differently."
It was found that among selected Co X-ides, Co3O4 was the winner. It demonstrated the best ECHQ performance with a high conversion of 98.2% and selectivity of 100% under ambient conditions. The Co3O4 sites present a higher proportion of 2-coordinated hydrogen-bonded water at the interface than other Co X-ides at a low negative potential, which enhances the kinetics of subsequent water dissociation to produce H*.
In comparison, the Co9S8 sites displayed the lowest ECHQ performance due to the high thermodynamic barrier in the H* formation step, which suppressed subsequent hydrogenation. Co(OH)F and CoP sites also had a low conversion of quinoline, due to high desorption barriers.
This study will help significantly advance our understanding of the catalytic mechanisms in ECHQ. These findings were published in Advanced Materials on September 2, 2024.
About the World Premier International Research Center Initiative (WPI)
The WPI program was launched in 2007 by Japan's Ministry of Education, Culture, Sports, Science and Technology (MEXT) to foster globally visible research centers boasting the highest standards and outstanding research environments. Numbering more than a dozen and operating at institutions throughout the country, these centers are given a high degree of autonomy, allowing them to engage in innovative modes of management and research. The program is administered by the Japan Society for the Promotion of Science (JSPS).
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Advanced Institute for Materials Research (AIMR)
Tohoku University
Establishing a World-Leading Research Center for Materials Science
AIMR aims to contribute to society through its actions as a world-leading research center for materials science and push the boundaries of research frontiers. To this end, the institute gathers excellent researchers in the fields of physics, chemistry, materials science, engineering, and mathematics and provides a world-class research environment.
Journal
Advanced Materials
Article Title
Identifying Highly Active and Selective Cobalt X-Ides for Electrocatalytic Hydrogenation of Quinoline
Article Publication Date
2-Sep-2024