Browsing by Author "Ozden, Adnan"
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Item Bipolar membrane electrolyzers enable high single-pass CO2 electroreduction to multicarbon products(Nature Research, 2022-06-24) Xie, Ke; Miao, Rui Kai; Ozden, Adnan; Liu, Shijie; Chen, Zhu; Dinh, Cao-Thang; Huang, Jianan Erick; Xu, Qiucheng; Gabardo, Christine M; Lee, Geonhui; Edwards, Jonathan P; O'Brien, Colin P; Boettcher, Shannon W; Sinton, David; Sargent, Edward HIn alkaline and neutral MEA CO2 electrolyzers, CO2 rapidly converts to (bi)carbonate, imposing a significant energy penalty arising from separating CO2 from the anode gas outlets. Here we report a CO2 electrolyzer uses a bipolar membrane (BPM) to convert (bi)carbonate back to CO2, preventing crossover; and that surpasses the single-pass utilization (SPU) limit (25% for multi-carbon products, C2+) suffered by previous neutral-media electrolyzers. We employ a stationary unbuffered catholyte layer between BPM and cathode to promote C2+ products while ensuring that (bi)carbonate is converted back, in situ, to CO2 near the cathode. We develop a model that enables the design of the catholyte layer, finding that limiting the diffusion path length of reverted CO2 to ~10 μm balances the CO2 diffusion flux with the regeneration rate. We report a single-pass CO2 utilization of 78%, which lowers the energy associated with downstream separation of CO2 by 10× compared with past systems.Item Carbon- and energy-efficient ethanol electrosynthesis via interfacial cation enrichment(Springer Science and Business Media LLC, 2024-10-04) Shayesteh Zeraati, Ali; Li, Feng; Tartela Alkayyali, Tartela; Dorakhan, Roham; Shirzadi, Erfan; Arabyarmohammadi, Fatemeh; O’Brien, Colin P; Gabardo, Christine M; Kong, Jonathan; Ozden, Adnan; Zargartalebi, Mohammad; Zhao, Yong; Fan, Lizhou; Papangelakis, Panagiotis; Kim, Dongha; Park, Sungjin; Miao, Rui Kai; Edwards, Jonathan P; Young, Daniel; Ip, Alexander H; Sargent, Edward H; Sinton, DavidThe use of acidic electrolytes in CO2 reduction avoids costly carbonate loss. However, the energy efficiency of acid-fed electrolysers has been limited by high hydrogen production and operating potentials. We find that these stem from the lack of alkali cations at the catalyst surface, limiting CO2 and CO adsorption. In acid-fed membrane electrode assembly systems, the incorporation of these cations is challenging as there is no flowing catholyte. Here an interfacial cation matrix (ICM)–catalyst heterojunction is designed that directly attaches to the catalyst layer. The negatively charged nature of the ICM enriches the alkali cation concentration near the cathode surface, trapping generated hydroxide ions. This increases the local electric field and pH, increasing multi-carbon production. Integrating the ICM strategy with a tailored copper–silver catalyst enables selective ethanol production through a proton-spillover mechanism. We report a 45% CO2-to-ethanol Faradaic efficiency at 200 mA cm−2, carbon efficiency of 63%, full-cell ethanol energy efficiency of 15% (3-fold improvement over the best previous acidic CO2 reduction value) and energy cost of 260 GJ per tonne ethanol, the lowest among reported ethanol-producing CO2 electrolysers.Item Carbon-efficient carbon dioxide electrolysers(Nature Research, 2022-05-12) Ozden, Adnan; García de Arquer, F. Pelayo; Huang, Jianan Erick; Wicks, Joshua; Sisler, Jared; Miao, Rui Kai; O’Brien, Colin P.; Lee, Geonhui; Wang, Xue; Ip, Alexander H.; Sargent, Edward H.; Sinton, DavidThe electroreduction of CO2 (CO2R) is the conversion of CO2 to renewable fuels and feedstocks, 35 a promising technology that could support the transition from fossil to renewable sources in the 36 chemical industry. Today the viability of CO2R technology is limited by carbonate formation – 37 via the reaction of reactant CO2 with hydroxides – and the energy cost incurred to regenerate the 38 reactant. In this Review, we analyse the literature on four emerging high single pass CO2 39 conversion approaches: CO2 regeneration from carbonate; CO2R in acidic media; cascade CO2R-40 COR; and CO2R direct from a capture liquid. We analyse each system, describe the challenges 41 associated with each pathway, and outline future research directions toward the goal of ensuring 42 CO2R is viable, and thus scalable.Item Cascade CO2 electroreduction enables efficient carbonate-free production of ethylene(Elsevier, 2021-02-15) Ozden, Adnan; Wang, Yuhang; Li, Fengwang; Luo, Mingchuan; Sisler, Jared; Thevenon, Arnaud; Rosas-Hernández, Alonso; Burdyny, Thomas; Lum, Yanwei; Yadegari, Hossein; Agapie, Theodor; Peters, Jonas C.; Sargent, Edward H.; Sinton, DavidCO2 electroreduction provides a route to convert waste emissions into chemicals such as ethylene (C2H4). However, the direct transformation of CO2-to-C2H4 suffers from CO2 loss to carbonate, consuming up to 72% of energy input. A cascade approach—coupling a solid-oxide CO2-to-CO electrochemical cell (SOEC) with a CO-to-C2H4 membrane electrode assembly (MEA)—would eliminate CO2 loss to carbonate. However, this approach requires a CO-to-C2H4 MEA with energy efficiency well beyond demonstrations to date. Focusing on the MEA, we find that an N-tolyl substituted tetrahydro-bipyridine film improves the stabilization of key reaction intermediates, while an SSC ionomer enhances CO transport to the Cu surface, enabling a C2H4 faradaic efficiency of 65% at 150 mA cm−2 for 110 h. Demonstrating a cascade SOEC-MEA approach, we achieve CO2-to-C2H4 with a ~48% reduction in energy intensity compared with the direct route. We further reduce the energy intensity by coupling CO electroreduction (CORR) with glucose electrooxidation.Item Catalyst synthesis under CO2 electroreduction favours faceting and promotes renewable fuels electrosynthesis(Nature Research, 2019-12-16) Wang, Yuhang; Wang, Ziyun; Dinh, Cao-Thang; Li, Jun; Ozden, Adnan; Kibria, Md Golam; Seifitokaldani, Ali; Tan, Chih-Shan; Gabardo, Christine M.; Luo, Mingchuan; Zhou, Hua; Li, Fengwang; Lum, Yanwei; McCallum, Christopher; Xu, Yi; Liu, Mengxia; Proppe, Andrew; Johnston, Andrew; Todorovic, Petar; Zhuang, Tao-Tao; Sinton, David; Kelley, Shana O.; Sargent, Edward H.The electrosynthesis of C2+ hydrocarbons from CO2 has attracted recent attention in light of the relatively high market price per unit energy input. Today’s low selectivities and stabilities towards C2+ products at high current densities curtail system energy efficiency, which limits their prospects for economic competitiveness. Here we present a materials processing strategy based on in situ electrodeposition of copper under CO2 reduction conditions that preferentially expose and maintain Cu(100) facets, which favour the formation of C2+ products. We observe capping of facets during catalyst synthesis and achieve control over faceting to obtain a 70% increase in the ratio of Cu(100) facets to total facet area. We report a 90% Faradaic efficiency for C2+ products at a partial current density of 520 mA cm−2 and a full-cell C2+ power conversion efficiency of 37%. We achieve nearly constant C2H4 selectivity over 65 h operation at 350 mA cm−2 in a membrane electrode assembly electrolyser.Item Cationic-group-functionalized electrocatalysts enable stable acidic CO2 electrolysis(Nature Research, 2023-09) Fan, Mengyang; Huang, Jianan Erick; Miao, Rui Kai; Mao, Yu; Ou, Pengfei; Li, Feng; Li, Xiao-Yan; Cao, Yufei; Zhang, Zishuai; Zhang, Jinqiang; Yan, Yu; Ozden, Adnan; Ni, Weiyan; Wang, Ying; Zhao, Yong; Chen, Zhu; Khatir, Behrooz; O’Brien, Colin P.; Xu, Yi; Xiao, Yurou Celine; Waterhouse, Geoffrey I. N.; Golovin, Kevin; Wang, Ziyun; Sargent, Edward H.; Sinton, DavidAcidic electrochemical CO2 reduction (CO2R) addresses CO2 loss and thus mitigates the energy penalties associated with CO2 recovery; however, acidic CO2R suffers low selectivity. One promising remedy—using a high concentration of alkali cations—steers CO2R towards multi-carbon (C2+) products, but these same alkali cations result in salt formation, limiting operating stability to <15 h. Here we present a copper catalyst functionalized with cationic groups (CG) that enables efficient CO2 activation in a stable manner. By replacing alkali cations with immobilized benzimidazolium CG within ionomer coatings, we achieve over 150 h of stable CO2R in acid. We find the water-management property of CG minimizes proton migration that enables operation at a modest voltage of 3.3 V with mildly alkaline local pH, leading to more energy-efficient CO2R with a C2+ Faradaic efficiency of 80 ± 3%. As a result, we report an energy efficiency of 28% for acidic CO2R towards C2+ products and a single-pass CO2 conversion efficiency exceeding 70%.Item Chloride-mediated selective electrosynthesis of ethylene and propylene oxides at high current density(American Association for the Advancement of Science, 2020-06-12) Leow, Wan Ru; Lum, Yanwei; Ozden, Adnan; Wang, Yuhang; Nam, Dae-Hyun; Chen, Bin; Wicks, Joshua; Zhuang, Tao-Tao; Li, Fengwang; Sinton, David; Sargent, Edward HChemicals manufacturing consumes large amounts of energy and is responsible for a substantial portion of global carbon emissions. Electrochemical systems that produce the desired compounds by using renewable electricity offer a route to lower carbon emissions in the chemicals sector. Ethylene oxide is among the world's most abundantly produced commodity chemicals because of its importance in the plastics industry, notably for manufacturing polyesters and polyethylene terephthalates. We applied an extended heterogeneous:homogeneous interface, using chloride as a redox mediator at the anode, to facilitate the selective partial oxidation of ethylene to ethylene oxide. We achieved current densities of 1 ampere per square centimeter, Faradaic efficiencies of ~70%, and product specificities of ~97%. When run at 300 milliamperes per square centimeter for 100 hours, the system maintained a 71(±1)% Faradaic efficiency throughout.Item CO2 electrolysis to multicarbon products in strong acid(American Association for the Advancement of Science, 2021-06-04) Huang, Jianan Erick; Li, Fengwang; Ozden, Adnan; Sedighian Rasouli, Armin; García de Arquer, F Pelayo; Liu, Shijie; Zhang, Shuzhen; Luo, Mingchuan; Wang, Xue; Lum, Yanwei; Xu, Yi; Bertens, Koen; Miao, Rui Kai; Dinh, Cao-Thang; Sinton, David; Sargent, Edward HCarbon dioxide electroreduction (CO2R) is being actively studied as a promising route to convert carbon emissions to valuable chemicals and fuels. However, the fraction of input CO2 that is productively reduced has typically been very low, <2% for multicarbon products; the balance reacts with hydroxide to form carbonate in both alkaline and neutral reactors. Acidic electrolytes would overcome this limitation, but hydrogen evolution has hitherto dominated under those conditions. We report that concentrating potassium cations in the vicinity of electrochemically active sites accelerates CO2 activation to enable efficient CO2R in acid. We achieve CO2R on copper at pH <1 with a single-pass CO2 utilization of 77%, including a conversion efficiency of 50% toward multicarbon products (ethylene, ethanol, and 1-propanol) at a current density of 1.2 amperes per square centimeter and a full-cell voltage of 4.2 volts.Item Constrained C2 adsorbate orientation enables CO-to-acetate electroreduction(Nature Research, 2023-05) Jin, Jian; Wicks, Joshua; Min, Qiuhong; Li, Jun; Hu, Yongfeng; Ma, Jingyuan; Wang, Yu; Jiang, Zheng; Xu, Yi; Lu, Ruihu; Si, Gangzheng; Papangelakis, Panagiotis; Shakouri, Mohsen; Xiao, Qunfeng; Ou, Pengfei; Wang, Xue; Chen, Zhu; Zhang, Wei; Yu, Kesong; Song, Jiayang; Jiang, Xiaohang; Qiu, Peng; Lou, Yuanhao; Wu, Dan; Mao, Yu; Ozden, Adnan; Wang, Chundong; Xia, Bao Yu; Hu, Xiaobing; Dravid, Vinayak P; Yiu, Yun-Mui; Sham, Tsun-Kong; Wang, Ziyun; Sinton, David; Mai, Liqiang; Sargent, Edward H; Pang, YuanjieThe carbon dioxide and carbon monoxide electroreduction reactions, when powered using low-carbon electricity, offer pathways to the decarbonization of chemical manufacture1,2. Copper (Cu) is relied on today for carbon-carbon coupling, in which it produces mixtures of more than ten C2+ chemicals3-6: a long-standing challenge lies in achieving selectivity to a single principal C2+ product7-9. Acetate is one such C2 compound on the path to the large but fossil-derived acetic acid market. Here we pursued dispersing a low concentration of Cu atoms in a host metal to favour the stabilization of ketenes10-chemical intermediates that are bound in monodentate fashion to the electrocatalyst. We synthesize Cu-in-Ag dilute (about 1 atomic per cent of Cu) alloy materials that we find to be highly selective for acetate electrosynthesis from CO at high *CO coverage, implemented at 10 atm pressure. Operando X-ray absorption spectroscopy indicates in situ-generated Cu clusters consisting of <4 atoms as active sites. We report a 12:1 ratio, an order of magnitude increase compared to the best previous reports, in the selectivity for acetate relative to all other products observed from the carbon monoxide electroreduction reaction. Combining catalyst design and reactor engineering, we achieve a CO-to-acetate Faradaic efficiency of 91% and report a Faradaic efficiency of 85% with an 820-h operating time. High selectivity benefits energy efficiency and downstream separation across all carbon-based electrochemical transformations, highlighting the importance of maximizing the Faradaic efficiency towards a single C2+ product11.Item Conversion of CO2 to multicarbon products in strong acid by controlling the catalyst microenvironment(Nature Research, 2023-02-09) Zhao, Yong; Hao, Long; Ozden, Adnan; Liu, Shijie; Miao, Rui Kai; Ou, Pengfei; Alkayyali, Tartela; Zhang, Shuzhen; Ning, Jing; Liang, Yongxiang; Xu, Yi; Fan, Mengyang; Chen, Yuanjun; Huang, Jianan Erick; Xie, Ke; Zhang, Jinqiang; O’Brien, Colin P.; Li, Fengwang; Sargent, Edward H.; Sinton, DavidElectrosynthesis of multicarbon products from the reduction of CO2 in acidic electrolytes is a promising approach to overcoming CO2 reactant loss in alkaline and neutral electrolytes; however, the proton-rich environment near the catalyst surface favours the hydrogen evolution reaction, leading to low energy efficiency for multicarbon products. Here we report a heterogeneous catalyst adlayer—composed of covalent organic framework nanoparticles and cation-exchange ionomers—that suppresses hydrogen evolution and promotes CO2-to-multicarbon conversion in strong acid. The imine and carbonyl-functionalized covalent organic framework regulates the ionomer structure, creating evenly distributed cation-carrying and hydrophilic–hydrophobic nanochannels that control the catalyst microenvironment. The resulting high local alkalinity and cation-enriched environment enables C–C coupling between 100 and 400 mA cm−2. A multicarbon Faradaic efficiency of 75% is achieved at 200 mA cm−2. The system demonstrates a full-cell multicarbon energy efficiency of 25%, which is a twofold improvement over the literature benchmark acidic system for the reduction of CO2.Item Cooperative CO2-to-ethanol conversion via enriched intermediates at molecule–metal catalyst interfaces(Nature Research, 2019-12-16) Li, Fengwang; Li, Yuguang C.; Wang, Ziyun; Li, Jun; Nam, Dae-Hyun; Lum, Yanwei; Luo, Mingchuan; Wang, Xue; Ozden, Adnan; Hung, Sung-Fu; Chen, Bin; Wang, Yuhang; Wicks, Joshua; Xu, Yi; Li, Yilin; Gabardo, Christine M.; Dinh, Cao-Thang; Wang, Ying; Zhuang, Tao-Tao; Sinton, David; Sargent, Edward H.Electrochemical conversion of CO2 into liquid fuels, powered by renewable electricity, offers one means to address the need for the storage of intermittent renewable energy. Here we present a cooperative catalyst design of molecule–metal catalyst interfaces with the goal of producing a reaction-intermediate-rich local environment, which improves the electrosynthesis of ethanol from CO2 and H2O. We implement the strategy by functionalizing the copper surface with a family of porphyrin-based metallic complexes that catalyse CO2 to CO. Using density functional theory calculations, and in situ Raman and operando X-ray absorption spectroscopies, we find that the high concentration of local CO facilitates carbon–carbon coupling and steers the reaction pathway towards ethanol. We report a CO2-to-ethanol Faradaic efficiency of 41% and a partial current density of 124 mA cm−2 at −0.82 V versus the reversible hydrogen electrode. We integrate the catalyst into a membrane electrode assembly-based system and achieve an overall energy efficiency of 13%.Item Doping Shortens the Metal/Metal Distance and Promotes OH Coverage in Non-Noble Acidic Oxygen Evolution Reaction Catalysts(ACS Publications, 2023-04-03) Wang, Ning; Ou, Pengfei; Miao, Rui Kai; Chang, Yuxin; Wang, Ziyun; Hung, Sung-Fu; Abed, Jehad; Ozden, Adnan; Chen, Hsuan-Yu; Wu, Heng-Liang; Huang, Jianan Erick; Zhou, Daojin; Ni, Weiyan; Fan, Lizhou; Yan, Yu; Peng, Tao; Sinton, David; Liu, Yongchang; Liang, Hongyan; Sargent, Edward HAcidic water electrolysis enables the production of hydrogen for use as a chemical and as a fuel. The acidic environment hinders water electrolysis on non-noble catalysts, a result of the sluggish kinetics associated with the adsorbate evolution mechanism, reliant as it is on four concerted proton-electron transfer steps. Enabling a faster mechanism with non-noble catalysts will help to further advance acidic water electrolysis. Here, we report evidence that doping Ba cations into a Co3O4 framework to form Co3-xBaxO4 promotes the oxide path mechanism and simultaneously improves activity in acidic electrolytes. Co3-xBaxO4 catalysts reported herein exhibit an overpotential of 278 mV at 10 mA/cm2 in 0.5 M H2SO4 electrolyte and are stable over 110 h of continuous water oxidation operation. We find that the incorporation of Ba cations shortens the Co-Co distance and promotes OH adsorption, findings we link to improved water oxidation in acidic electrolyte.Item Efficient CO and acrolein co-production via paired electrolysis(Springer Nature, 2024-07) Wang, Xue; Li, Peihao; Tam, Jason; Howe, Jane Y.; O’Brien, Colin P.; Sedighian Rasouli, Armin; Miao, Rui Kai; Liu, Yuan; Ozden, Adnan; Xie, Ke; Wu, Jinhong; Sinton, David; Sargent, Edward H.Paired electrolysis—the combination of a productive cathodic reaction, such as CO2 electroreduction (CO2RR), with selective oxidation on the anode—provides an electrified reaction with maximized atom and energy efficiencies. Unfortunately, direct electro-oxidation reactions typically exhibit limited Faradaic efficiencies (FEs) towards a single product. Here we apply paired electrolysis for acidic CO2RR and the model organic oxidation allyl alcohol oxidation reaction to acrolein. This CO2RR alcohol oxidation reaction system shows (96 ± 1)% FE of CO2 to CO on the cathode and (85 ± 1)% FE of allyl alcohol to acrolein on the anode. As a result of this pairing with organic oxidation on the anode, the full-cell voltage of the system is lowered by 0.7 V compared with the state-of-art acidic CO2-to-CO studies at the same 100 mA cm−2 current density. The acidic cathode avoids carbonate formation and enables a single-pass utilization of CO2 of 84% with a 6× improvement in the atom efficiency of CO2 utilization. Energy consumption analysis suggests that, when producing the same amount of CO, the system reduces energy consumption by an estimated 1.6× compared with the most energy-efficient prior acidic CO2-to-CO ambient-temperature electrolysis systems. The work suggests that paired electrolysis could be a decarbonization technology to contribute to a sustainable futureItem Efficient electrically powered CO2-to-ethanol via suppression of deoxygenation(Nature Research, 2020-05-11) Wang, Xue; Wang, Ziyun; García de Arquer, F. Pelayo; Dinh, Cao-Thang; Ozden, Adnan; Li, Yuguang C.; Nam, Dae-Hyun; Li, Jun; Liu, Yi-Sheng; Wicks, Joshua; Chen, Zitao; Chi, Miaofang; Chen, Bin; Wang, Ying; Tam, Jason; Howe, Jane Y.; Proppe, Andrew; Todorović, Petar; Li, Fengwang; Zhuang, Tao-Tao; Gabardo, Christine M.; Kirmani, Ahmad R.; McCallum, Christopher; Hung, Sung-Fu; Lum, Yanwei; Luo, Mingchuan; Min, Yimeng; Xu, Aoni; O’Brien, Colin P.; Stephen, Bello; Sun, Bin; Ip, Alexander H.; Richter, Lee J.; Kelley, Shana O.; Sinton, David; Sargent, Edward H.The carbon dioxide electroreduction reaction (CO2RR) provides ways to produce ethanol but its Faradaic efficiency could be further improved, especially in CO2RR studies reported at a total current density exceeding 10 mA cm−2. Here we report a class of catalysts that achieve an ethanol Faradaic efficiency of (52 ± 1)% and an ethanol cathodic energy efficiency of 31%. We exploit the fact that suppression of the deoxygenation of the intermediate HOCCH* to ethylene promotes ethanol production, and hence that confinement using capping layers having strong electron-donating ability on active catalysts promotes C–C coupling and increases the reaction energy of HOCCH* deoxygenation. Thus, we have developed an electrocatalyst with confined reaction volume by coating Cu catalysts with nitrogen-doped carbon. Spectroscopy suggests that the strong electron-donating ability and confinement of the nitrogen-doped carbon layers leads to the observed pronounced selectivity towards ethanol.Item Efficient electrocatalytic conversion of carbon dioxide in a low-resistance pressurized alkaline electrolyzer(Elsevier, 2019-12-23) Edwards, Jonathan P.; Xu, Yi; Gabardo, Christine M.; Dinh, Cao-Thang; Li, Jun; Qi, ZhenBang; Ozden, Adnan; Sargent, Edward H.; Sinton, DavidElectrochemical carbon dioxide conversion offers a means to utilize carbon dioxide and simultaneously store excess renewable energy. To be economical, industrial carbon dioxide electroreduction systems require high energy efficiencies to minimize electrical input. To this end, these systems need high product selectivity at low cell voltages and industrially viable current densities. Here, a liquid phase flow cell electrolyzer using a silver catalyst for carbon dioxide conversion to carbon monoxide is reported. Significant improvements in cell efficiency are demonstrated through the synergistic combination of three factors: minimal electrode spacing (0.25 mm flow field), pressurization (50 bar), and alkalinity (5 M KOH). Diminished electrode spacings reduce ohmic losses, pressurization increases carbon monoxide selectivities, and alkaline conditions improve reaction kinetics. The combination of these three factors enables an uncorrected full cell energy efficiency of 67% at 202 mA/cm2, the highest reported above 150 mA/cm2. This system maintains a competitive energy efficiency of 47% at a high current density of 941 mA/cm2.Item Efficient electrosynthesis of n-propanol from carbon monoxide using a Ag–Ru–Cu catalyst(Nature Research, 2022-02-10) Wang, Xue; Ou, Pengfei; Ozden, Adnan; Hung, Sung-Fu; Tam, Jason; Gabardo, Christine M.; Howe, Jane Y.; Sisler, Jared; Bertens, Koen; García de Arquer, F. Pelayo; Miao, Rui Kai; O’Brien, Colin P.; Wang, Ziyun; Abed, Jehad; Rasouli, Armin Sedighian; Sun, Mengjia; Ip, Alexander H.; Sinton, David; Sargent, Edward H.The high-energy-density C3 fuel n-propanol is desired from CO2/CO electroreduction, as evidenced by propanol’s high market price per tonne (approximately US$ 1,400–1,600). However, CO electroreduction to n-propanol has shown low selectivity, limited production rates and poor stability. Here we report catalysts, identified using computational screening, that simultaneously facilitate multiple carbon–carbon coupling, stabilize C2 intermediates and promote CO adsorption, all leading to improved n-propanol electrosynthesis. Experimentally we construct the predicted optimal electrocatalyst based on silver–ruthenium co-doped copper. We achieve, at 300 mA cm−2, a high n-propanol Faradaic efficiency of 36% ± 3%, a C2+ Faradaic efficiency of 93% and single-pass CO conversion of 85%. The system exhibits 100 h stable n-propanol electrosynthesis. Technoeconomic analysis based on the performance of the pilot system projects profitability.Item Efficient Methane Electrosynthesis Enabled by Tuning Local CO2 Availability(American Chemical Society, 2020-01-28) Wang, Xue; Xu, Aoni; Li, Fengwang; Hung, Sung-Fu; Nam, Dae-Hyun; Gabardo, Christine M; Wang, Ziyun; Xu, Yi; Ozden, Adnan; Rasouli, Armin Sedighian; Ip, Alexander H; Sinton, David; Sargent, Edward HThe electroreduction of carbon dioxide (CO2RR) to valuable chemicals is a promising avenue for the storage of intermittent renewable electricity. Renewable methane, obtained via CO2RR using renewable electricity as energy input, has the potential to serve as a carbon-neutral fuel or chemical feedstock, and it is of particular interest in view of the well-established infrastructure for its storage, distribution, and utilization. However, CO2RR to methane still suffers from low selectivity at commercially relevant current densities (>100 mA cm-2). Density functional theory calculations herein reveal that lowering *CO2 coverage on the Cu surface decreases the coverage of the *CO intermediate, and then this favors the protonation of *CO to *CHO, a key intermediate for methane generation, compared to the competing step, C-C coupling. We therefore pursue an experimental strategy wherein we control local CO2 availability on a Cu catalyst by tuning the concentration of CO2 in the gas stream and regulate the reaction rate through the current density. We achieve as a result a methane Faradaic efficiency (FE) of (48 ± 2)% with a partial current density of (108 ± 5) mA cm-2 and a methane cathodic energy efficiency of 20% using a dilute CO2 gas stream. We report stable methane electrosynthesis for 22 h. These findings offer routes to produce methane with high FE and high conversion rate in CO2RR and also make direct use of dilute CO2 feedstocks.Item Electroosmotic flow steers neutral products and enables concentrated ethanol electroproduction from CO2(Elsevier, 2021-10-20) Miao, Rui Kai; Xu, Yi; Ozden, Adnan; Robb, Anthony; O’Brien, Colin P.; Gabardo, Christine M.; Lee, Geonhui; Edwards, Jonathan P.; Huang, Jianan Erick; Fan, Mengyang; Wang, Xue; Liu, Shijie; Yan, Yu; Sargent, Edward H.; Sinton, DavidElectrochemical reduction of carbon dioxide (CO2RR) converts intermittent renewable energy into high energy density fuels, such as ethanol. Membrane electrode assembly (MEA) electrolyzers are particularly well-suited to CO2-to-ethanol conversion in view of their low ohmic resistance and high stability. However, over 75% of the ethanol produced at the cathode migrates through the membrane where it is diluted by the anolyte and may be oxidized. The ethanol concentration that results is two orders of magnitude below the 10 wt% standard set by the incumbent industrial process, fermentation. Here, we reverse the direction of ion and electroosmotic transport by means of a porous proton exchange layer, and thereby block both the convective and diffusive routes of ethanol loss. With this strategy, we eliminate ethanol crossover to the anode (< 1%), and achieve an ethanol concentration of 13.1 wt% directly from the cathode outlet.Item Eliminating the need for anodic gas separation in CO2 electroreduction systems via liquid-to-liquid anodic upgrading(Nature Research, 2022-06-02) Xie, Ke; Ozden, Adnan; Miao, Rui Kai; Li, Yuhang; Sinton, David; Sargent, Edward H.Electrochemical reduction of CO2 to multi-carbon products (C2+), when powered using renewable electricity, offers a route to valuable chemicals and fuels. In conventional neutral-media CO2-to-C2+ devices, as much as 70% of input CO2 crosses the cell and mixes with oxygen produced at the anode. Recovering CO2 from this stream adds a significant energy penalty. Here we demonstrate that using a liquid-to-liquid anodic process enables the recovery of crossed-over CO2 via facile gas-liquid separation without additional energy input: the anode tail gas is directly fed into the cathodic input, along with fresh CO2 feedstock. We report a system exhibiting a low full-cell voltage of 1.9 V and total carbon efficiency of 48%, enabling 262 GJ/ton ethylene, a 46% reduction in energy intensity compared to state-of-art single-stage CO2-to-C2+ devices. The strategy is compatible with today’s highest-efficiency electrolyzers and CO2 catalysts that function optimally in neutral and alkaline electrolytes.Item Energy- and Carbon-efficient CO2 Electrolysis(2022-11) Ozden, Adnan; Sinton, David; Mechanical and Industrial EngineeringCarbon dioxide/monoxide (CO2/CO) reduction (CO2R/COR) – when powered by renewable electricity – provides a sustainable means to convert emissions into valuable products for the manufacturing, transport, and chemical industries. CO2R can contribute to sustainability through closing the carbon loop, increasing the penetration of renewables in the petrochemical industry, and achieving long-term storage of renewable electricity. Despite considerable promise, there have yet been few demonstrations of CO2R with a rate, energy efficiency, and carbon efficiency that would bring techno-economics in line with incumbents. The main objective of the thesis is to contribute to the realization of energy- and carbon-efficient CO2R. The first three technical chapters of this thesis focus on improving the performance metrics in flow cells and membrane electrode assembly electrolyzers (Chapters 3, 4, and 5). The last two technical chapters focus on implementing the performance-boosting strategies into carbonate-formation-free systems to achieve simultaneously high carbon and energy efficiencies (Chapters 6 and 7). The first work reports a new catalyst design that decouples gas, ion, and electron transport and enables, for the first time, CO2R at activities greater than 1 A cm−2 in alkaline flow cell electrolyzers (Chapter 3). Then, low overpotential and high selectivity in CO2R is achieved via an adparticle functionalization catalyst: gold adparticles formed on the silver-gold alloying interface via galvanic replacement (Chapter 4). A molecule:ionomer hierarchy is developed to lower the activation barrier for C–C coupling and control CO2, water, and proton transport – which in turn enabled record energy efficiency towards ethylene at industrially relevant reaction rates (Chapter 5). A cascade system – CO2R to CO in a solid oxide electrolysis cell (SOEC) with zero carbonate formation and COR to C2+ products in a MEA electrolyzer – is developed to achieve record low energy intensities in the electrosynthesis of C2+ products (Chapter 6). Finally, a catalyst microenvironment exhibiting cation repulsion and anion attraction is developed to combine practical energy- and carbon-efficiency in electrosynthesis of C2+ from CO2/CO feedstocks (Chapter 7).