Browsing by Author "Dorakhan, Roham"
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Item Acid-Stable Cu Cluster Precatalysts Enable High Energy and Carbon Efficiency in CO2 Electroreduction(ACS, 2024-10-09) Kim, Dongha; Park, Sungjin; Lee, Junwoo; Chen, Yiqing; Li, Feng; Kim, Jiheon; Bai, Yang; Huang, Jianan Erick; Liu, Shijie; Jung, Eui Dae; Lee, Byoung-Hoon; Papangelakis, Panagiotis; Ni, Weiyan; Alkayyali, Tartela; Miao, Rui Kai; Li, Peihao; Liang, Yongxiang; Shayesteh Zeraati, Ali; Dorakhan, Roham; Meira, Debora Motta; Chen, Yanna; Sinton, David; Zhong, Mingjiang; Sargent, Edward HThe electrochemical reduction of CO2 in acidic media offers the advantage of high carbon utilization, but achieving high selectivity to C2+ products at a low overpotential remains a challenge. We identified the chemical instability of oxide-derived Cu catalysts as a reason that advances in neutral/alkaline electrolysis do not translate to acidic conditions. In acid, Cu ions leach from Cu oxides, leading to the deactivation of the C2+-active sites of Cu nanoparticles. This prompted us to design acid-stable Cu cluster precatalysts that are reduced in situ to active Cu nanoparticles in strong acid. Operando Raman and X-ray spectroscopy indicated that the bonding between the Cu cluster precatalyst ligand and in situ formed Cu nanoparticles preserves a high density of undercoordinated Cu sites, resulting in a C2H4 Faradaic efficiency of 62% at a low overpotential. The result is a 1.4-fold increase in energy efficiency compared with previous acidic CO2-to-C2+ electrocatalytic 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 CO2 electroreduction to multicarbon products from carbonate capture liquid(Elsevier, 2023-05-26) Lee, Geonhui; Rasouli, Armin Sedighian; Lee, Byoung-Hoon; Zhang, Jinqiang; Won, Da Hye; Xiao, Yurou Celine; Edwards, Jonathan P.; Lee, Mi Gyoung; Jung, Eui Dae; Arabyarmohammadi, Fatemeh; Liu, Hengzhou; Grigioni, Ivan; Abed, Jehad; Alkayyali, Tartela; Liu, Shijie; Xie, Ke; Miao, Rui Kai; Park, Sungjin; Dorakhan, Roham; Zhao, Yong; O’Brien, Colin P.; Chen, Zhu; Sinton, David; Sargent, EdwardAlkali hydroxide systems capture CO2as carbonate; however, generating a pure CO2stream requires significant energy input, typically from thermal cycling to 900 C. What is more, the subsequent valorization of gas-phase CO2into products presents additional energy requirements and system complexities, including man-aging the formation of (bi)carbonate in an electrolyte and separating unreacted CO2downstream. Here, we report the direct electrochemical conversion of CO2, captured in the form of carbon-ate, into multicarbon (C2+) products. Using an interposer and a Cu/CoPc-CNTs electrocatalyst, we achieve 47% C2+Faradaic efficiency at 300 mA cm 2and a full cell voltage of 4.1 V. We report 56 wt % ofC2H4and no detectable C1gas in the product gas stream: CO, CH4,and CO2combined total below 0.9 wt % (0.1 vol %). This approach obviates the need for energy to regenerate lost CO2, an issue seen in prior CO2-to-C2+reportsItem Ligand-modified nanoparticle surfaces influence CO electroreduction selectivity(Nature Research, 2024-04-06) Shirzadi, Erfan; Jin, Qiu; Zeraati, Ali Shayesteh; Dorakhan, Roham; Goncalves, Tiago J; Abed, Jehad; Lee, Byoung-Hoon; Rasouli, Armin Sedighian; Wicks, Joshua; Zhang, Jinqiang; Ou, Pengfei; Boureau, Victor; Park, Sungjin; Ni, Weiyan; Lee, Geonhui; Tian, Cong; Meira, Debora Motta; Sinton, David; Siahrostami, Samira; Sargent, Edward HImproving the kinetics and selectivity of CO2/CO electroreduction to valuable multi-carbon products is a challenge for science and is a requirement for practical relevance. Here we develop a thiol-modified surface ligand strategy that promotes electrochemical CO-to-acetate. We explore a picture wherein nucleophilic interaction between the lone pairs of sulfur and the empty orbitals of reaction intermediates contributes to making the acetate pathway more energetically accessible. Density functional theory calculations and Raman spectroscopy suggest a mechanism where the nucleophilic interaction increases the sp2 hybridization of CO(ad), facilitating the rate-determining step, CO* to (CHO)*. We find that the ligands stabilize the (HOOC-CH2)* intermediate, a key intermediate in the acetate pathway. In-situ Raman spectroscopy shows shifts in C-O, Cu-C, and C-S vibrational frequencies that agree with a picture of surface ligand-intermediate interactions. A Faradaic efficiency of 70% is obtained on optimized thiol-capped Cu catalysts, with onset potentials 100 mV lower than in the case of reference Cu catalysts.Item Pathways to reduce the energy cost of carbon monoxide electroreduction to ethylene(Elsevier, 2024-05-15) Alkayyali, Tartela; Zargartalebi, Mohammad; Ozden, Adnan; Arabyarmohammadi, Fatemeh; Dorakhan, Roham; Edwards, Jonathan P.; Li, Feng; Shayesteh Zeraati, Ali; Fan, Mengyang; Bazylak, Aimy; Sargent, Edward H.; Sinton, DavidCO2 -to-CO conversion, followed by CO to value-added products, shows promise as a high-CO2 utilization strategy. However, it is necessary to continue to reduce the energy intensity of CO electrolysers. Modeling can untangle the highly coupled nature of these electrolysers and thereby accelerate their optimization. Here, we develop a CO electrolyser model, which we compare with experiments, and evaluate how it might be possible to attain CO-to-ethylene with the energy intensity approaching 110 GJ tonne-1 C 2 H4 , then further to an 80 GJ tonne-1 C 2 H4 target. The model identifies targets and specifications for each component, with the ultimate target requiring continued progress in increasing cathodic catalyst selectivity; thin anion exchange membranes (<25 μm); improved ion exchange capacity (1.7 – 3.4 mmol/g); enhanced anode activity (>56% overpotential reduction) and thickness (100 – 400 μm); and optimized operation (1 – 4 M KOH at 25 – 75°C) at >300 mA cm -2 .Item Progress and roadmap for electro-privileged transformations of bio-derived molecules(Nature Research, 2024-04) Tian, Cong; Dorakhan, Roham; Wicks, Joshua; Chen, Zhu; Choi, Kyoung-Shin; Singh, Nirala; Schaidle, Joshua A.; Holewinski, Adam; Vojvodic, Aleksandra; Vlachos, Dionisios G.; Broadbelt, Linda J.; Sargent, Edward H.Biomass incorporates carbon captured from the atmosphere and can serve as a renewable feedstock for producing valuable chemicals and fuels. Here we look at how electrochemical approaches can impact biomass valorization, focusing on identifying chemical transformations that lever renewable electricity and feedstocks to produce valorized products via electro-privileged transformations. First, we recommend that the field explore widening the spectrum of platform chemicals derived from bio-feedstocks, thus offering pathways to molecules that have historically been derived from petroleum. Second, we identify opportunities in electrocatalytic production of energy-dense fuels from biomass that utilize water as the hydrogen source and renewable electricity as the driving force. Finally, we look at the potential in electrochemical depolymerization to preserve key functional groups in raw feedstocks that would otherwise be lost during harsh pre-treatments in traditional depolymerization routes. Based on these priorities, we suggest a roadmap for the integration of biomass and electrochemistry and we offer milestones required to tap further into the potential of electrochemical biomass valorization.Item Selective Electrified Propylene-to-Propylene Glycol Oxidation on Activated Rh-Doped Pd(American Chemical Society, 2024-03-27) Huang, Jianan Erick; Chen, Yiqing; Ou, Pengfei; Ding, Xueda; Yan, Yu; Dorakhan, Roham; Lum, Yanwei; Li, Xiao-Yan; Bai, Yang; Wu, Chengqian; Fan, Mengyang; Lee, Mi Gyoung; Miao, Rui Kai; Liu, Yanjiang; O'Brien, Colin; Zhang, Jinqiang; Tian, Cong; Liang, Yongxiang; Xu, Yi; Luo, Mingchuan; Sinton, David; Sargent, Edward HRenewable-energy-powered electrosynthesis has the potential to contribute to decarbonizing the production of propylene glycol, a chemical that is used currently in the manufacture of polyesters and antifreeze and has a high carbon intensity. Unfortunately, to date, the electrooxidation of propylene under ambient conditions has suffered from a wide product distribution, leading to a low faradic efficiency toward the desired propylene glycol. We undertook mechanistic investigations and found that the reconstruction of Pd to PdO occurs, followed by hydroxide formation under anodic bias. The formation of this metastable hydroxide layer arrests the progressive dissolution of Pd in a locally acidic environment, increases the activity, and steers the reaction pathway toward propylene glycol. Rh-doped Pd further improves propylene glycol selectivity. Density functional theory (DFT) suggests that the Rh dopant lowers the energy associated with the production of the final intermediate in propylene glycol formation and renders the desorption step spontaneous, a concept consistent with experimental studies. We report a 75% faradic efficiency toward propylene glycol maintained over 100 h of operation.Item Selective synthesis of butane from carbon monoxide using cascade electrolysis and thermocatalysis at ambient conditions(Nature Research, 2023-04-03) Lee, Mi Gyoung; Li, Xiao-Yan; Ozden, Adnan; Wicks, Joshua; Ou, Pengfei; Li, Yuhang; Dorakhan, Roham; Lee, Jaekyoung; Park, Hoon Kee; Yang, Jin Wook; Chen, Bin; Abed, Jehad; dos Reis, Roberto; Lee, Geonhui; Huang, Jianan Erick; Peng, Tao; Chin, Ya-Huei; Sinton, David; Sargent, Edward H.It is of interest to extend the reach of CO2 and CO electrochemistry to the synthesis of products with molecular weights higher than the C1 and C2 seen in most prior reports carried out near ambient conditions. Here we present a cascade C1–C2–C4 system that combines electrochemical and thermochemical reactors to produce C4H10 selectively at ambient conditions. In a C2H4 dimerization reactor, we directly upgrade the gas outlet stream of the CO2 or CO electrolyser without purification. We find that CO, which is present alongside C2H4, enhances C2H4 dimerization selectivity to give C4H10 to 95%, a much higher performance than when a CO2 electrolyser is used instead. We achieve an overall two-stage CO-to-C4H10 cascade selectivity of 43%. Mechanistic investigations, complemented by density functional theory calculations reveal that increased CO coverage favours C2H4 dimerization and hydrogenation of *CxHy adsorbates, as well as destabilizes the *C4H9 intermediate, and so promotes the selective production of the target alkane.Item A silver–copper oxide catalyst for acetate electrosynthesis from carbon monoxide(Nature Research, 2023-03-13) Dorakhan, Roham; Grigioni, Ivan; Lee, Byoung-Hoon; Ou, Pengfei; Abed, Jehad; O’Brien, Colin; Sedighian Rasouli, Armin; Plodinec, Milivoj; Miao, Rui Kai; Shirzadi, Erfan; Wicks, Joshua; Park, Sungjin; Lee, Geonhui; Zhang, Jinqiang; Sinton, David; Sargent, Edward H.Acetic acid is an important chemical feedstock. The electrocatalytic synthesis of acetic acid from CO2 offers a low-carbon alternative to traditional synthetic routes, but the direct reduction from CO2 comes with a CO2 crossover energy penalty. CO electroreduction bypasses this, which motivates the interest in a cascade synthesis approach of CO2 to CO followed by CO to acetic acid. Here we report a catalyst design strategy in which off-target intermediates (such as ethylene and ethanol) in the reduction of CO to acetate are destabilized. On the optimized Ag–CuO2 catalyst, this destabilization of off-target intermediates leads to an acetate Faradaic efficiency of 70% at 200 mA cm−2. We demonstrate 18 hours of stable operation in a membrane electrode assembly; the system produced 5 wt% acetate at 100 mA cm−2 and a full-cell energy efficiency of 25%, a twofold improvement on the highest energy-efficient electrosynthesis in prior reports.Item Site-selective protonation enables efficient carbon monoxide electroreduction to acetate(2024-01) Wang, Xinyue; Chen, Yuanjun; Li, Feng; Miao, Rui Kai; Huang, Jianan Erick; Zhao, Zilin; Li, Xiao-Yan; Dorakhan, Roham; Chu, Senlin; Wu, Jinhong; Zheng, Sixing; Ni, Weiyan; Kim, Dongha; Park, Sungjin; Liang, Yongxiang; Ozden, Adnan; Ou, Pengfei; Hou, Yang; Sinton, David; Sargent, Edward HElectrosynthesis of acetate from CO offers the prospect of a low-carbon-intensity route to this valuable chemical--but only once sufficient selectivity, reaction rate and stability are realized. It is a high priority to achieve the protonation of the relevant intermediates in a controlled fashion, and to achieve this while suppressing the competing hydrogen evolution reaction (HER) and while steering multicarbon (C2+) products to a single valuable product--an example of which is acetate. Here we report interface engineering to achieve solid/liquid/gas triple-phase interface regulation, and we find that it leads to site-selective protonation of intermediates and the preferential stabilization of the ketene intermediates: this, we find, leads to improved selectivity and energy efficiency toward acetate. Once we further tune the catalyst composition and also optimize for interfacial water management, we achieve a cadmium-copper catalyst that shows an acetate Faradaic efficiency (FE) of 75% with ultralow HER (<0.2% H2 FE) at 150 mA cm-2. We develop a high-pressure membrane electrode assembly system to increase CO coverage by controlling gas reactant distribution and achieve 86% acetate FE simultaneous with an acetate full-cell energy efficiency (EE) of 32%, the highest energy efficiency reported in direct acetate electrosynthesis.Item Strong-Proton-Adsorption Co-Based Electrocatalysts Achieve Active and Stable Neutral Seawater Splitting(Wiley, 2023-01-31) Wang, Ning; Ou, Pengfei; Hung, Sung-Fu; Huang, Jianan Erick; Ozden, Adnan; Abed, Jehad; Grigioni, Ivan; Chen, Clark; Miao, Rui Kai; Yan, Yu; Zhang, Jinqiang; Wang, Ziyun; Dorakhan, Roham; Badreldin, Ahmed; Abdel-Wahab, Ahmed; Sinton, David; Liu, Yongchang; Liang, Hongyan; Sargent, Edward HDirect electrolysis of pH-neutral seawater to generate hydrogen is an attractive approach for storing renewable energy. However, due to the anodic competition between the chlorine evolution and the oxygen evolution reaction (OER), direct seawater splitting suffers from a low current density and limited operating stability. Exploration of catalysts enabling an OER overpotential below the hypochlorite formation overpotential (≈490 mV) is critical to suppress the chloride evolution and facilitate seawater splitting. Here, a proton-adsorption-promoting strategy to increase the OER rate is reported, resulting in a promoted and more stable neutral seawater splitting. The best catalysts herein are strong-proton-adsorption (SPA) materials such as palladium-doped cobalt oxide (Co3- x Pdx O4 ) catalysts. These achieve an OER overpotential of 370 mV at 10 mA cm-2 in pH-neutral simulated seawater, outperforming Co3 O4 by a margin of 70 mV. Co3- x Pdx O4 catalysts provide stable catalytic performance for 450 h at 200 mA cm-2 and 20 h at 1 A cm-2 in neutral seawater. Experimental studies and theoretical calculations suggest that the incorporation of SPA cations accelerates the rate-determining water dissociation step in neutral OER pathway, and control studies rule out the provision of additional OER sites as a main factor herein.Item Supramolecular tuning of supported metal phthalocyanine catalysts for hydrogen peroxide electrosynthesis(Nature Research, 2023-03-13) Lee, Byoung-Hoon; Shin, Heejong; Rasouli, Armin Sedighian; Choubisa, Hitarth; Ou, Pengfei; Dorakhan, Roham; Grigioni, Ivan; Lee, Geonhui; Shirzadi, Erfan; Miao, Rui Kai; Wicks, Joshua; Park, Sungjin; Lee, Hyeon Seok; Zhang, Jinqiang; Chen, Yuanjun; Chen, Zhu; Sinton, David; Hyeon, Taeghwan; Sung, Yung-Eun; Sargent, Edward H.Two-electron oxygen reduction offers a route to H2O2 that is potentially cost-effective and less energy-intensive than the industrial anthraquinone process. However, the catalytic performance of the highest performing prior heterogeneous electrocatalysts to H2O2 has lain well below the >300 mA cm−2 needed for capital efficiency. Herein, guided by computation, we present a supramolecular approach that utilizes oxygen functional groups in a carbon nanotube substrate that—when coupled with a cobalt phthalocyanine catalyst—improve cobalt phthalocyanine adsorption, preventing agglomeration; and that further generate an electron-deficient Co centre whose interaction with the key H2O2 intermediate is tuned towards optimality. The catalysts exhibit an overpotential of 280 mV at 300 mA cm−2 with turnover frequencies over 50 s−1 in a neutral medium, an order of magnitude higher activity compared with the highest performing prior H2O2 electrocatalysts. This performance is sustained for over 100 h of operation.Item Tuning of Pd Clusters and their Local Environment for CH4 and CO Oxidation Reactions(2020-11) Dorakhan, Roham; Chin, Ya-Huei (Cathy); Chemical Engineering Applied ChemistryPd clusters are active catalysts for oxidation of CH4 and CO, the major components of exhaust gas emissions and significant greenhouse gasses. Addition of Pt enhances the reactivity of Pd for either oxidation reaction by modifying the electronic properties of the Pd. This thesis explored (i) the optimum Pd-to-Pt atomic ratio for CH4 and CO oxidation reactions and (ii) the effects local Pd site environment alteration by confining of the clusters in SSZ-13 zeolite pores and the resulting dynamic interconversions among small and large Pd clusters. The optimal Pt-to-Pd atomic ratio was between 0.2 and 0.3, maximizing Pd-Pt interactions. In SSZ-13 zeolites, reversible re-dispersion was achieved using subsequent treatments under O2 and H2, and 10 kPa O2 partial pressure during CH4-O2 reactions was found to maximize the Pd cluster dispersion. The modifications on Pd clusters explored in this thesis could help produce more active (Pt incorporation into Pd) and stable (Pd supported on SSZ-13) exhaust emission catalysts that are less prone to sintering.