Metal-free Carbon as an effective catalyst for hydrogen peroxide production

Significance 

Rice scientists treated metal-free carbon black, the inexpensive, powdered product of petroleum production, with oxygen plasma. The process introduces defects and oxygen-containing groups into the structure of the carbon particles, exposing more surface area for interactions. Researchers have created a “defective” catalyst that simplifies the generation of hydrogen peroxide from oxygen. The research by Rice chemist James Tour and Boris Yakobson appears in the American Chemical Society journal ACS Catalysis.

When used as a catalyst, the defective particles known as CB-Plasma reduce oxygen to hydrogen peroxide with 100% Faradaic efficiency, a measure of charge transfer in electrochemical reactions. The process shows promise to replace the complex anthraquinone-based production method that requires expensive catalysts and generates toxic organic byproducts and large amounts of wastewater, according to the researchers.

Hydrogen peroxide is widely used as a disinfectant, as well as in wastewater treatment, in the paper and pulp industries and for chemical oxidation. The authors hope the new process will influence the design of hydrogen peroxide catalysts going forward.

The electrochemical process outlined in their study needs no metal catalysts, and this will lower the cost and make the entire process far simpler. Proper engineering of carbon structure could provide suitable active sites that reduce oxygen molecules while maintaining the O-O bond, so that hydrogen peroxide is the only product. Besides that, the metal-free design helps prevent the decomposition of hydrogen peroxide.

Plasma processing creates defects in carbon black particles that appear as five- or seven-member rings in the material’s atomic lattice. The process sometimes removes enough atoms to create vacancies in the lattice. The catalyst works by pulling two electrons from oxygen, allowing it to combine with two hydrogen electrons to create hydrogen peroxide. (Reducing oxygen by four electrons, a process used in fuel cells, produces water as a byproduct.)

The research team also treated carbon black with ultraviolet-ozone and treated CB-Plasma after oxygen reduction with argon to remove most of the oxygen-containing groups. CB-UV was no better at catalysis than plain carbon black, but CB-Argon performed just as well as CB-Plasma with an even wider range of electrochemical potential, the lab reported.

Because the exposure of CB-Plasma to argon under high temperature removed most of the oxygen groups, the authors inferred the carbon defects themselves were responsible for the catalytic reduction to hydrogen peroxide.

The simplicity of the process could allow more local generation of the valuable chemical, reducing the need to transport it from centralized plants. CB-Plasma matches the efficiency of state-of-the-art materials now used to generate hydrogen peroxide. Scaling this process is much easier than present methods, and it is so simple that even small units could be used to generate hydrogen peroxide at the sites of need.

Metal-free Carbon as an effective catalyst for hydrogen peroxide production - Advances in Engineering
A transmission electron microscope image shows details of carbon black particles after treatment with plasma. Defects in the carbon lattice caused by the oxygen plasma enhance the material’s ability to catalyze the production of hydrogen peroxide, according to Rice University scientists. Credit: Tour Group/Yakobson Research Group/Rice University
Metal-free Carbon as an effective catalyst for hydrogen peroxide production - Advances in Engineering
FIGURE: Scientists at Rice University have introduced plasma-treated carbon black as a simple and highly efficient catalyst for the production of hydrogen peroxide. Defects created in the carbon provide more catalytic sites to reduce oxygen to hydrogen peroxide. Credit: Tour Group/Yakobson Research Group/Rice University.

About the author

Professor James Tour is T. T. and W. F. Chao Professor of Chemistry and Professor of Materials Science & NanoEngineering. Tour has about 650 research publications and over 200 patents, with an H-index = 129 and i10 index = 538 with total citations over 77,000 (Google Scholar). He was inducted into the National Academy of Inventors in 2015.

Tour’s scientific research areas include nanoelectronics, graphene electronics, silicon oxide electronics, carbon nanovectors for medical applications, green carbon research for enhanced oil recovery and environmentally friendly oil and gas extraction, graphene photovoltaics, carbon supercapacitors, lithium ion batteries, lithium metal batteries, CO2 capture, water splitting to H2 and O2, water purification, carbon nanotube and graphene synthetic modifications, graphene oxide, carbon composites, hydrogen storage on nanoengineered carbon scaffolds, and synthesis of single-molecule nanomachines which includes molecular motors and nanocars and nanomachines that can drill through cell membranes.

Reference

Zhe Wang, Qin-Kun Li, Chenhao Zhang, Zhihua Cheng, Weiyin Chen, Emily A. McHugh, Robert A. Carter, Boris I. Yakobson, and James M. Tour. Hydrogen Peroxide Generation with 100% Faradaic Efficiency on Metal-Free Carbon Black, ACS Catal. 2021, 11, 4, 2454–2459

Go To ACS Catal

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