Hakhyeon Song

Electrochemical CO2 reduction (CO2RR) offers an environmentally friendly method to transform and harness sequestered CO2. While gas-phase electrolysis systems provide high efficiency, gas-phase electrolysis systems face challenges related to carbonate precipitate formation and crossover. In response, liquid-phase (bi)carbonates electrolysis systems based on the use of bipolar membrane (BPM) electrode assemblies have emerged. These systems not only streamline the carbon-capture and conversion process but also present economic benefits. However, liquid-phase (bi)carbonate electrolysis cells suffer limited stability and selectivity at relevant operating current. Here, utilizing a Ni-based single-atom catalyst (Ni-SAC) and bicarbonate electrolyte, we demonstrate exceptional CO Faradaic efficiency (93%) at a partial current density of -186 mA cm-2 at -3.7 V for over 18 hours with an integrated carbon …

Electrochemical nitrate reduction reaction (NO3RR) has garnered increasing attention as a pathway for converting a harmful pollutant (nitrate) into a value‐added product (ammonia). However, high selectivity toward ammonia (NH3) is imperative for process viability. Optimizing proton availability near the catalyst is important for achieving selective NH3 production. Here, the aim is to systematically examine the impacts of proton availability on NO3RR selectivity in a bipolar membrane (BPM)‐based membrane electrode assembly (MEA) system. The BPM generates a proton flux from the membrane toward the catalyst during electrolysis. Thus, the BPM‐MEA system can modulate the proton flux during operation. The impact of interposer layers, proton scavenging electrolytes (CO32−), and catalyst configurations are also examined to identify which local microenvironments favor ammonia formation. It is found that a …

Electrochemical CO2 reduction has attracted significant interest as a pathway for achieving a carbon-neutral society. However, conventional gas-phase CO2 electrolysis cell configurations often face challenges like low CO2 utilization efficiency due to carbonate crossover, and costly integration with carbon capture systems. The membrane electrode assembly (MEA) electrolysis cell configuration involving a bipolar membrane (BPM) has been recently spotlighted as this system can directly release CO2 stored in carbonate solutions using a pH swing process driven by water dissociation within the BPM. Here, we assess the reactor’s capacity to liberate CO2 and facilitate its conversion into ethylene (C2H4), using Cu–Ag catalysts and carbon capture solutions such as potassium carbonate (K2CO3). Bench-top flow cell system testing using an optimized Cu–Ag electrocatalyst demonstrates that the conversion of CO2 to …

The two-electrons (2e–) oxygen reduction reaction (ORR) offers a sustainable and decentralized alternative to the traditional synthetics for hydrogen peroxide (H2O2) production. Although various Co single atom catalysts (SACs) have been proposed as highly effective 2e– ORR catalysts, there is still room for improvement through fine-tuned coordination environment. Here, a Co-N5-O-C with the combination of highly coordinated Co-N5 moieties and nearby electro-withdrawing epoxides is first time developed to reach the optimal binding energy of *OOH intermediate, resulting in the ultrahigh mass activity of 87.5 A g−1 at 0.75 V vs. RHE. Moreover, a high H2O2 production rate of 11.3 mol g−1 h−1 at 200 mA cm−2 is also obtained by a flow cell device. Such an efficient in-situ generation of H2O2 further enables 100% degradation of the organic methylene blue pollutant within 15 min through the electro-Fenton …

Polymer electrolyte membrane (PEM) electrolysis is considered a promising technology for the renewable hydrogen production from renewable energy, due to the high energy efficiency and robust design of the PEM cells.1 Nevertheless, despite their attractiveness, PEM cells did not find wide implementation for other electrochemical transformations than water splitting. The main reason is the low faradaic efficiencies of reduction reactions at the cathode of PEM cells, due to the competing hydrogen evolution reaction (HER), highly favorable in the acidic electrolyte environment of the PEM cell. We investigated the electrochemical nitrate reduction reaction at the cathode side of a PEM cell, aiming at reaching high faradaic efficiency and selectivity towards a single reaction product, and at the same time, high single pass nitrate conversion.Nitrates represent one of the most prominent ground water pollutants, and …

In article number 2208996, Pyuck-Pa Choi, Stefan Ringe, Jihun Oh, and co-workers report the synthesis of Cu–ceria-nanorod catalysts for electrochemical CO 2 reduction. The ceria nanorods help CuO exist as several cluster layers at the interface. Through the strong metal–support interaction between Cu and ceria, Cu can be stably loaded on ceria nanorods in a mixed oxidation state at the Cu/ceria interface, which facilitates CO–CO dimerization, resulting in high-efficiency selective ethylene production.

Carbon dioxide conversion systems are important to drive down the cost of carbon capture through the creation of valuable products. However, how to integrate carbon capture with carbon conversion devices is not yet clear. Bipolar membrane electrolyzers have attracted significant interest as a device which is compatible with carbon capture, as these systems can operate with bicarbonate and carbonate-based solutions. In a bipolar membrane electrolyzer, carbonate is converted to carbon dioxide through a pH swing process driven by water dissociation within the bipolar membrane. However, balancing the rate of water dissociation, carbon dioxide production, and carbon dioxide electrocatalysis remains a critical challenge. Furthermore, steering carbon dioxide electrocatalysis toward a specific high value product such as ethylene is unclear.Here, we set out to examine the activity of Cu, Ag and CuAg catalyst in a …

ConspectusHere, we discuss recent advances and pressing challenges in achieving sustainable urea synthesis. Urea stands out as the most prevalent nitrogen-based fertilizer used across the globe, making up over 50% of all manufactured fertilizers. Historically, the Bosch-Meiser process has been the go-to chemical manufacturing method for urea production. This procedure, characterized by its high-temperature and high-pressure conditions, reacts ammonia with carbon dioxide to form ammonium carbamate. Subsequently, this ammonium carbamate undergoes dehydration, facilitated by heat, producing solid urea. A concerning aspect of this method is its dependency on fossil fuels, as nearly all the process heat comes from nonrenewable sources. Consequently, the Bosch-Meiser process leaves behind a considerable carbon footprint. Current estimates predict that unchecked, carbon emissions from urea …

Electrochemical CO2 reduction (CO2RR) has attracted significant interest as a pathway for achieving a carbon-neutral society. However, conventional gas-phase CO2 electrolysis configurations suffer from low CO2 utilization and expensive integration with carbon capture. Here, we demonstrate experimentally how a bipolar membrane (BPM) membrane electrode assembly (MEA) electrolysis cell can convert CO2 released from carbon capture solutions (K2CO3) directly into ethylene (C2H4). Using an optimized Cu-Ag electrocatalyst we demonstrate the conversion of CO2 to C2H4 with a 10% Faradaic efficiency (with a partial current density of 10 mA cm-2). During all tests, the BPM-MEA electrolysis cell also achieved ~100% CO2 utilization efficiency over 24 hours. Additionally, we discuss the impact of the cost of electricity and water loss play on the economic feasibility of BPM-MEA systems.

Ammonia is the key ingredient for living organisms, and artificial catalytic synthesis of ammonia (known as the Haber-Bosch process) is undoubtedly a milestone in scientific research in the 20th century and the cornerstone of today's society.[1] However, the Haber-Bosch process is energy-intensive (2% of the global energy consumption) and is accompanied by large CO2 emissions (1% of global CO2 emission).[2] To catch up with the goal of “Net Zero CO2 Emissions” by 2050, it is imperative to develop a carbon-free and sustainable ammonia production process. The photocatalytic ammonia synthesis method relies only on renewable feedstocks (water and air) and sustainable energy input (light) and can be operated under ambient conditions. The current progress in photocatalytic ammonia synthesis suggests, however, there exists a large gap in performance before commercial use is viable. To replace the …

The electrochemical conversion of CO2 to ethanol and ethylene is an environmentally and economically promising method for addressing global climate change in a carbon-neutral society. Ethanol is desirable because of its high energy density. However, ethanol production is less favored than ethylene production on Cu catalysts. Alloys have gained prominence as a catalyst that enhances ethanol selectivity. In this study, metallic CuZn alloys with different Zn contents (Cu, Cu9Zn1, Cu3Zn1, and Cu2Zn1) were fabricated by co-sputtering Cu and Zn. A maximum ethanol/ethylene ratio of 9.2 was achieved on Cu2Zn1, which is 11 times higher than that of the Cu catalyst. Furthermore, we prepared Cu9Zn1 on polytetrafluoroethylene (PTFE), which achieved an ethanol partial density of approximately 93 mA cm−2 at −0.76 V vs. RHE. Cu9Zn1/PTFE exhibited stable ethanol production with ∼25% faradaic efficiency and …

Next Generation Electrochemistry (NGenE) is an annual, week-long summer workshop focused on discussing emerging challenges at the frontiers of research in electrochemistry, centered on the next generation of scientists. Since 2016, NGenE has broadened the perspective of senior graduate students and postdoctoral researchers from all over the United States. A series of world-renowned experts in electrochemical science and technology examine fundamental phenomena at an advanced level, identifying critical gaps in our understanding that demand innovative strategies of research and development. The program assumes baseline knowledge in electrochemistry. NGenE does not ask “What is electrochemistry?” but instead

Metal oxides are a promising material for designing highly active and selective catalysts for the electrochemical reduction of carbon dioxide (CO2RR). Here, we designed a Cu/ceria catalyst with high selectivity of methane production at single-atomic Cu active sites. Using this, we report favorable design concepts that push the product selectivity of methane formation by combining detailed structural analysis, density functional theory (DFT), in situ Raman spectroscopy, and electrochemical measurements. We demonstrate that a higher concentration of oxygen vacancies on the catalyst surface, resulting from more available Cu+ sites, enables high selectivity for methane formation during CO2RR and can be controlled by the calcination temperature. The DFT calculation and in situ Raman studies indicate that pH controls the surface termination; a more alkaline pH generates hydroxylated surface motifs with more active …

After the Industrial Revolution, we have achieved remarkable technological advances. Until just a few decades ago, we thought that damaging the environment was not a big problem for technological advancement. However, recently, too many adverse effects are plaguing us in all areas around us such as extreme weather, and etc. due to excessive environmental destruction. In order to solve these environmental problems, the development of innovative green energy technologies is essential. In particular, electrochemical carbon dioxide reduction is considered one of the most promising technologies for future energy because it can convert carbon dioxide in the atmosphere into fuels or chemicals including C1 (carbon monoxide, formic acid, and methanol) to C2 products (acetate acid, ethylene, ethanol, and n-propanol). Cu is a unique metal catalyst that can produce a variety of hydrocarbons and oxygenates with acceptable amount. However, it is necessary to improve the performance such as selectivity, current density, and stability for industrially relevant application. Especially, selectivity in Cu-based catalysts is highly affected by the complicated interactions of a lot of reaction intermediates derived from CO2 and protons. Accordingly, it is important for Cu-based catalysts to control the coverage and kinetics of intermediates for selective reaction pathways. In this dissertation, we aim to present the strategies for the efficient and selective CO2RR products formation in Cu-based catalysts. We controlled the coverage and kinetics of intermediates in Cu-based catalysts by changing local electrolysis environment inducing the selective activation of the …

DSpace at KOASAS: Effect of CO2 Partial Pressure on C2H4 Reaction Pathways in Electrochemicacl CO2 reduction KOASAS menu About KOASAS KAIST Library 검색 Advanced Search Browse Communities & Collections Researchers at KAIST Titles Subject By Date rss_1.0 rss_2.0 atom_1.0 sherpa SEARCH DSpace at KOASAS College of Engineering(공과대학)Dept. of Materials Science and Engineering(신소재공학과)MS-Conference Papers(학술회의논문) Effect of CO2 Partial Pressure on C2H4 Reaction Pathways in Electrochemicacl CO2 reduction Cited 0 time in webofscience Cited 0 time in scopus Hit : 71 Download : 0 Export DC(XML) Excel Song, Hakhyeon / Oh, Jihunresearcher Publisher KAIST, KIChE Issue Date 2021-07-21 Language English Citation 18th International Conference on Carbon Dioxide Utilization, ICCDU 2021 URI http://hdl.handle.net/10203/291695 Appears in Collection MS-Conference …

The glycerol electro-oxidation reaction (GEOR) can economically convert glycerol, a byproduct of biodiesel production, to glycolic acid. Herein, nanostructured Au catalysts were fabricated on a Si substrate by the electrochemical reduction of anodic-treated (RA-treatment) Au films, which tuned the surface area from 1 to 16 cm2. Treatment of 0.1 M glycerol at 1.0 V (vs RHE) for 2 h in 1 M KOH solution afforded a glycerol conversion and glycolic acid selectivity of 50.9 and 47%, respectively. The RA-Au catalyst selectively afforded glycolic acid from glycerol due to the enhanced facet-dependent OH adsorption, especially at the (100) and (110) sites, as well as the increased surface area. RA treatment of a Au-coated Ni foam further enhanced the GEOR performance, affording 68.7% glycerol conversion and 41.2% glycolic acid selectivity at 1.0 V (vs RHE) within 2 h by providing more active sites.

The direct utilization of CO2 from flue gas bypasses the need for costly carbon capture and purification processes and thus presents a potentially more economical approach to create chemical feedstocks and fuels. In this work, essential system design parameters required for a CO2 electrolyzer to perform efficient electroproduction of formate from a simulated flue gas feed at industrially relevant activities have been identified. In addition to the use of effective catalysts and gas-diffusion electrodes, we demonstrate that the efficiency of formate production in a dilute CO2 environment is highly sensitive to the feed flow rate, which is directly related to the local CO2 concentration. If the flow condition is not optimal under dilute CO2 conditions, the carbonation reaction dominates and limits CO2 availability for formate production. Ultimately, we have established basic system design guidelines to overcome CO2 deficiency in …

Electrochemical reduction of CO2 on copper-based catalysts has become a promising strategy to mitigate greenhouse gas emissions and gain valuable chemicals and fuels. Unfortunately, however, the generally low product selectivity of the process decreases the industrial competitiveness compared to the established large-scale chemical processes. Here, we present random solid solution Cu1–xNix alloy catalysts that, due to their full miscibility, enable a systematic modulation of adsorption energies. In particular, we find that these catalysts lead to an increase of hydrogen evolution with the Ni content, which correlates with a significant increase of the selectivity for methane formation relative to C2 products such as ethylene and ethanol. From experimental and theoretical insights, we find the increased hydrogen atom coverage to facilitate Langmuir–Hinshelwood-like hydrogenation of surface intermediates, giving …

Flow electrolyzers based on gas-diffusion electrodes (GDEs) have been increasingly employed to advance toward industry-relevant electrochemical CO2 reduction reaction (CO2RR) performance, though fundamental understanding of the GDE system is still lacking. Here, we propose that regulating local CO2 concentration on copper (Cu) surfaces is an effective and general strategy to promote C−C coupling in CO2RR. Local CO2 concentration could influence the surface coverage of ∗CO2, ∗H, and ∗CO, which affects the reaction pathways toward multi-carbon (C2+) products. Guided by mass-transport modeling, we have identified three approaches to modulate the local CO2 concentration in GDE-based electrolyzers: (1) catalyst layer structure, (2) feed CO2 concentration, and (3) feed flow rate. Utilizing Cu2O nanoparticles as the model catalysts, modulation of local CO2 concentration enabled an optimized …

Partially positive-charged copper (Cuδ+) is known to boost the formation of highly valued multicarbon C2+ products during the electrochemical CO2 reduction reaction (CO2RR). In this work, we doped boron in copper oxide (B–CuO) to create Cuδ+ sites and studied two important aspects regarding the CO2RR: (1) the direct observation of the CO reaction intermediate on the Cuδ+ surface and (2) the role of Cuδ+ in enhancing C2+ selectivity. Operando attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) showed that distinct CO intermediates were present on CuO and B–CuO surfaces during the CO2RR. We observed that multiple CO adsorption sites and strong adsorption of the CO intermediate on the Cuδ+ surface promote the C–C coupling reaction in B–CuO. As a result, we achieved a C2+ Faradaic efficiency of 62.1% at −0.62 V versus reversible hydrogen electrode on …