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      Performance Characteristics of Polymer Electrolyte Membrane CO 2 Electrolyzer: Effect of CO 2 Dilution, Flow Rate and Pressure

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      Journal of The Electrochemical Society
      The Electrochemical Society

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          Abstract

          CO 2 electrolyzer designed to operate on dilute CO 2 feed and low stoichiometric ratio would alleviate the separation costs for CO 2 purification and electrolyzer exit gas processing, respectively. The effect of CO 2 concentration, CO 2 flow rate, and CO 2 pressure on current density and faradaic efficiency of a solid polymer electrolyte membrane CO 2 electrolyzer was quantified. An approach for estimating voltage breakdown into activation overpotential for CO 2 reduction reaction as well as oxygen evolution reaction, ohmic losses, and concentration overpotential is introduced. No enhancement in current density (∼160 mA cm −2) was observed above stoichiometry ratio of 4 whereas reducing the stoichiometric ratio to 2.7 still yielded a current density of ∼100 mA cm −2. Dilution of CO 2 in the feed from 100 mol% to 30 mol%, at ∼90kPa of cell pressure, resulted in a monotonically decreasing current density. A square root dependency on CO2 partial pressure was observed under these conditions. Operation with pure CO 2 at different total pressure yielded only a minor increase in current density indicating some form of saturation-limited behavior. Long-term potentiostatic operation over 85 h revealed continuous drop in current density and a corresponding increase in electrode resistance, observed in electrochemical impedance response.

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          Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives

          We review the fundamental aspects of metal oxides, metal chalcogenides and metal pnictides as effective electrocatalysts for the oxygen evolution reaction. There is still an ongoing effort to search for sustainable, clean and highly efficient energy generation to satisfy the energy needs of modern society. Among various advanced technologies, electrocatalysis for the oxygen evolution reaction (OER) plays a key role and numerous new electrocatalysts have been developed to improve the efficiency of gas evolution. Along the way, enormous effort has been devoted to finding high-performance electrocatalysts, which has also stimulated the invention of new techniques to investigate the properties of materials or the fundamental mechanism of the OER. This accumulated knowledge not only establishes the foundation of the mechanism of the OER, but also points out the important criteria for a good electrocatalyst based on a variety of studies. Even though it may be difficult to include all cases, the aim of this review is to inspect the current progress and offer a comprehensive insight toward the OER. This review begins with examining the theoretical principles of electrode kinetics and some measurement criteria for achieving a fair evaluation among the catalysts. The second part of this review acquaints some materials for performing OER activity, in which the metal oxide materials build the basis of OER mechanism while non-oxide materials exhibit greatly promising performance toward overall water-splitting. Attention of this review is also paid to in situ approaches to electrocatalytic behavior during OER, and this information is crucial and can provide efficient strategies to design perfect electrocatalysts for OER. Finally, the OER mechanism from the perspective of both recent experimental and theoretical investigations is discussed, as well as probable strategies for improving OER performance with regards to future developments.
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            Powering the planet: chemical challenges in solar energy utilization.

            Global energy consumption is projected to increase, even in the face of substantial declines in energy intensity, at least 2-fold by midcentury relative to the present because of population and economic growth. This demand could be met, in principle, from fossil energy resources, particularly coal. However, the cumulative nature of CO(2) emissions in the atmosphere demands that holding atmospheric CO(2) levels to even twice their preanthropogenic values by midcentury will require invention, development, and deployment of schemes for carbon-neutral energy production on a scale commensurate with, or larger than, the entire present-day energy supply from all sources combined. Among renewable energy resources, solar energy is by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year. In view of the intermittency of insolation, if solar energy is to be a major primary energy source, it must be stored and dispatched on demand to the end user. An especially attractive approach is to store solar-converted energy in the form of chemical bonds, i.e., in a photosynthetic process at a year-round average efficiency significantly higher than current plants or algae, to reduce land-area requirements. Scientific challenges involved with this process include schemes to capture and convert solar energy and then store the energy in the form of chemical bonds, producing oxygen from water and a reduced fuel such as hydrogen, methane, methanol, or other hydrocarbon species.
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              Carbon capture and storage (CCS): the way forward

              Carbon capture and storage (CCS) is vital to climate change mitigation, and has application across the economy, in addition to facilitating atmospheric carbon dioxide removal resulting in emissions offsets and net negative emissions. This contribution reviews the state-of-the-art and identifies key challenges which must be overcome in order to pave the way for its large-scale deployment. Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO 2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO 2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.
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                Author and article information

                Contributors
                Journal
                Journal of The Electrochemical Society
                J. Electrochem. Soc.
                The Electrochemical Society
                0013-4651
                1945-7111
                June 17 2022
                June 01 2022
                June 17 2022
                June 01 2022
                : 169
                : 6
                : 064510
                Article
                10.1149/1945-7111/ac725f
                c611189b-10fb-4d7a-bb0f-64aef73967e8
                © 2022

                http://creativecommons.org/licenses/by/4.0/

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