The metal-carbon dioxide battery is a promising and environmentally friendly technology, but its energy efficiency is limited. Recently, a research team led by chemists from the City University of Hong Kong (CityU) discovered an innovative way to overcome this problem by introducing an unconventional phase nanomaterial as a catalyst, boosting the battery’s energy efficiency by up to 83.8%. The study reveals a new catalyst design for the new generation of meta-gas batteries that can contribute to carbon neutral goals. The metal-carbon dioxide battery can provide durable electricity (high energy density) for electronics and enable carbon dioxide (CO2) fixation without additional energy consumption from an external circuit to convert the greenhouse gas CO2 emissions into products added value (Figure 1). In particular, the lithium dioxide battery has a high theoretical energy density (1876 Wh kg-1), making it a promising candidate for next-generation high-efficiency energy conversion and storage technology. However, metal CO2 batteries still suffer from sluggish reaction kinetics. This causes large overpotential (ie, more voltage or energy is required than theoretically determined to drive the oxidation-reduction reaction that makes the battery work), low energy efficiency, poor reversibility, and limited cycle stability. Technical barriers to traditional catalyst modification strategies “Researchers typically consider the morphology, size, components, and distribution of metal-based components in composite cathode catalysts as the main concerns that lead to differences in battery performance,” said Dr. and one of the study leaders. “But we found that preparing new catalysts with unconventional phases is a feasible and promising strategy to enhance the energy efficiency and performance of metal-gas batteries, especially since traditional modification strategies for catalysts have faced long-term technical hurdles.” Dr. Fan and his team accumulated extensive experience and knowledge on fine-tuning the crystal phase of metal-based nanomaterials, which allowed them to select suitable elements to construct their unconventional phases and then study the effect of the crystal phase of catalysts in the reaction kinetics of a specific type of aprotic (i.e., not involving hydrogen ions) metal-gas electrochem. “However, this does not mean that this process is easy to perform because it involves strict requirements regarding the bifunctionality of cathode catalysts in an organic environment,” explained Dr. Fan. The team synthesized iridium nanostructures with an unusual 4H/face cubic (fcc) heterophase by controlling the growth kinetics of Ir on gold (Au) templates. In their experiments, the 4H/fcc heterophase catalyst showed a lower charge level (below 3.61 V) and a higher energy efficiency of up to 83.8% during cycling in aprotic Li-CO2 batteries than other catalysts based on metal (typically chargeable above 3.8V and energy efficiency up to 75%). Figure 2. Three different kinds of kinetic electrochemical reactions on [email protected], [email protected] and pure Au (right panel) in an aprotic Li-CO2 battery. Credit: Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2204666119 Excellent performance of unconventional phase metal nanomaterials The team’s combination of experiments and theoretical calculations revealed that 4H/fcc Ir nanostructures created via mechanical phasing are more favorable for the reversible formation of amorphous/low crystallinity discharge products (Figure 2), thereby reducing overpotential and promoting recycling stability of electrochemical redox reactions. The unusual 4H/fcc phase Ir nanostructures far outperformed common fcc Ir and achieved excellent charge potential and energy efficiency compared to other reported metal-based catalysts used in aprotic Li-CO2 batteries. “This study reveals the great potential of mechanical phase catalysts in metal-gas electrochemistry. It opens a new direction in catalyst design for the development of sustainable electrochemical energy conversion and storage systems,” concluded Dr. The findings were recently published in Proceedings of the National Academy of Sciences (PNAS), entitled “Enhancement of reaction kinetics in aprotic lithium-carbon dioxide batteries with unconventional phase metal nanomaterials.” More information: Jingwen Zhou et al, Enhancing reaction kinetics in aprotic lithium-carbon dioxide batteries with unconventional phase metal nanomaterials, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2204666119 Provided by City University of Hong Kong (CityU) Reference: Chemists boost eco-friendly battery performance using catalysts with unconventional phase nanostructures (2022, November 16) Retrieved November 16, 2022 from This document is subject to copyright. 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