Bifunctional CoFeP-N nanowires synthesized for sustainable water splitting

Peer-Reviewed Publication

HEFEI INSTITUTES OF PHYSICAL SCIENCE, CHINESE ACADEMY OF SCIENCES

 

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SCHEMATIC DIAGRAM OF EFFICIENT ELECTROCATALYTIC WATER SPLITTING BY COFEP-N NANOWIRES

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CREDIT: WANG RUIQI

A recent study led by Prof. WANG Qi's research group from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences successfully synthesized iron and nitrogen co-doped CoFeP-N nanowires for high-efficiency electrocatalytic water splitting.

Their findings, published in Applied Catalysis B: Environment and Energy, demonstrate the synthesis of bifunctional CoFeP-N nanowires for both hydrogen and oxygen evolution.

Hydrogen production by electrolysis uses water as the only raw material to achieve a closed cycle of hydrogen gas with zero carbon emissions, which is considered to be the greenest and most sustainable method. However, high costs limit the wide application of hydrogen production by electrolysis, requiring more cost-effective and efficient catalysts. Due to its low cost and high catalytic performance, transition metal-based nanomaterials, which are abundant on Earth, have been proven to have broad prospects as excellent electrocatalysts.

In this study, researchers introduced various heteroatoms into the carrier to form a transition metal-based nanocomposite using a three-step synthesis method of hydrothermal phosphatizing and low temperature plasma treatment. They successfully prepared bifocal CoFeP-N nanowires for hydrogen and oxygen evolution to achieve synergistic interactions with the catalyst.

This project uses doping engineering, interface engineering, and plasma treatment to make the performance of transition metal catalysts, potentially surpassing precious metal catalysts, while maintaining good cycling stability. This helps us reduce production costs and promote industrial upgrading.

After preparing CoFeP-N catalyst into an electrolysis cell, its electrocatalytic water splitting performance can exceed that of commercial precious metal electrolysis cells under the same conditions. In addition, it can work continuously for more than 100 hours without obvious performance degradation.

This work presents an effective method for preparing transition metal based bifunctional electrocatalysts, opening new avenues for the production of efficient, stable, and affordable advanced and sustainable energy materials.

Bifunctional CoFeP-N Nanowires Synthesized for Sustainable Water Splitting 

 Theoretical calculations illustrate the efficient electrocatalytic water splitting mechanism of CoFeP-N nanowires

CREDIT

WANG Ruiqi

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JOURNAL

Applied Catalysis B Environment and Energy

ARTICLE TITLE

Low-temperature plasma-assisted synthesis of iron and nitrogen co-doped CoFeP-N nanowires for high-efficiency electrocatalytic water splitting

USTC develops efficient tandem catalyst to enhance nitrate electroreduction to ammonia

UNIVERSITY OF SCIENCE AND TECHNOLOGY OF CHINA

 

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(A) CO3O4/ CU1-N-C AND (B) CU1-N-C AT −0.8V VS RHE IN 1 M NO3- WITH DIFFERENT DISTANCES RANGING FROM 0 TO 200ΜM; (C) FREE ENERGY DIAGRAM OF NO3- ELECTROREDUCTION OVER CUN4 AND CO3O4 (100) SLABS. *REPRESENTS AN ADSORPTION SITE. 

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CREDIT: YAN LIU, JIE WEI ET AL.

A research team led by Prof. ZENG Jie and Prof. GENG Zhigang from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) has designed a tandem catalyst to improve the electroreduction of nitrate into ammonia. By coupling Cu single atoms catalysts with adjacent Co3O4 nanosheets, the team successfully regulated the adsorption energy of intermediates in the nitrate electroreduction process, promoting the synthesis of ammonia. Their findings were published in Nature Communications.

Converting nitrate (NO3-) from wastewater into ammonia (NH3) not only offers an effective approach of wastewater treatment but also holds promise as a sustainable method for ammonia synthesis. However, the diverse adsorption configurations of nitrogen-containing intermediates in the NO3- electroreduction process pose a challenge, making it difficult for a single catalyst to optimize adsorption simultaneously. While Cu-based electrocatalyst are advantageous for NO3- adsorption, one key issue is the excessive accumulation of nitrite (NO2-) which would result in the rapid deactivation of catalysts and sluggish kinetics of subsequent hydrogenation steps.

To overcome these limitations, the researchers designed a tandem electrocatalyst by combining Cu single atoms anchored on N-doped carbon with adjacent Co3O4 nanosheets (denoted as Co3O4/Cu1-N-C). This innovative combination leverages the strengths of both components: Cu's ability to adsorb NO3- and Co3O4's ability to adsorb NO2-. This dual-function catalyst aims to optimize the binding energies of intermediates, thereby facilitating the electroreduction process from NO3- to NH3 more efficiently.

Specifically, the researchers synthesized the Co3O4/Cu1-N-C catalyst through a series of steps, including the pyrolysis of Cu-doped ZIF-8 to obtain Cu single atoms on N-doped carbon, followed by the deposition of Co3O4 nanosheets. The structure and composition of the catalyst were characterized using various techniques such as high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray absorption near edge structure (XANES) spectroscopy. These analyses confirmed the successful combination of Cu single atoms and Co3O4 nanosheets, as well as the uniform distribution of the catalytic centers.

Finally, performance testing of the catalysts was conducted in a three-electrode H-type cell, with the concentration of NH3 product quantified using the indophenol blue method. The test revealed that Co3O4/Cu1-N-C achieved an ammonia production rate of 114.0 mgNH3h-1cm-2 in the NO3- electroreduction reaction, which was 2.2 times and 3.6 times as high as that of Cu1-N-C and Co3O4, respectively. Mechanistic investigations showed that Co3O4 effectively regulates the adsorption configuration of NO2- and enhances its binding, thereby accelerating the overall electroreduction process from NO3- to NH3.

This research highlights a novel approach to addressing the limitations of single catalysts in nitrate electroreduction by using a tandem catalyst system. It not only provides a deeper understanding of the catalytic mechanisms involved but also sets the stage for future developments in the design of advanced electrocatalysts for similar applications.

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JOURNAL

Nature Communications

DOI

10.1038/s41467-024-48035-4 

ARTICLE TITLE

Efficient tandem electroreduction of nitrate into ammonia through coupling Cu single atoms with adjacent Co3O4