Electrocatalysis and Electrochemical Systems are Key for a Sustainable Future
Welcome visiting our research website at Iowa State! Sustainable energy and advanced manufacturing are two of our grand needs. Innovations in these areas have the potential to transform our nation’s prosperity and security. Advanced electrochemical systems such as fuel cells, batteries and electrolyzers can generate, store, and utilize renewable electricity, thus enabling distributed, flexible and modular chemicals manufacturing towards a sustainable future.
Our interdisciplinary research is at the interface between Science and Engineering. We have strong interest in elucidating electrochemical reaction pathways and mechanisms, and based on the acquired understanding, we rationally design electrocatalysts and electrochemical devices for important energy and environmental applications. Our current research activities include development of advanced electrocatalysts, novel electrochemical processes and systems, electroreduction of nitrate to nitrogen gas and valuable nitrogen-containing chemicals, carbon dioxide electro-reduction, ammonia electrosynthesis, seawater splitting for hydrogen production, and electrochemical synthesis of hydrogen peroxide.
Electrocatalytic Hydrogenation and Oxidation of Biorenewable Compounds
Electrochemical reduction of biomass-derived platform chemicals is an emerging route for the sustainable production of fuels and chemicals, however, understanding gaps between reaction conditions, underlying mechanisms, and observed products have limited the rational design of active, stable, and selective catalyst systems. We started our research on selective electrochemical reduction of levulinic acid (LA) to valeric acid (VA) or γ-valerolactone (gVL) on a non-precious Pb electrode in a polymer electrolyte membrane electrocatalytic flow cell reactor, which demonstrated very high yield of VA (>90%) and high faradaic efficiency (>86%). Electrode potential and electrolyte pH were found to tune the reduction products.
We explored the mechanisms of the electrochemical reduction of furfural, an important biobased platform molecule and model for aldehyde reduction, through a combination of voltammetry, preparative electrolysis, thiol-electrode modifications, and kinetic isotope studies. We found that the two isomers of hydrofuroin are generated from a direct electroreduction mechanism, while furfuryl alcohol and methyl furan are produced from electrocatalytic hydrogenation (ECH). Understanding the underlying mechanisms enabled us to manipulate the products of furfural reduction by rationally tuning the electrode potential, electrolyte pH, and furfural concentration to promote selective formation of important biobased polymer precursors and fuels. Our current research is focused on detailed mechanism study of C=O reduction, as well as development of electrochemical flow cells that can integrate the oxidation and reduction of biorenewable compounds for biopolymer synthesis. This research is collaborated with Prof. JP Tessonnier.
Recently, we have demonstrated one paired electrolyzer for electrocatalytic hydrogenation and oxidation of 5-(hydroxymethyl)furfural to produce two biorenewable monomers with a combined electron efficiency of 187%.
We are currently working on the development of flow paired electrolyzers for efficient production of chemicals and monomers from distributed, inexpensive, renewable furanic feedstock. We are collaborating with Prof. Eric Cochran on to develop new furanic polyesters.
Xiaotong Chadderdon, David Chadderdon, John Matthiesen, Yang Qiu, Jack Carraher, Jean-Philippe Tessonnier, Wenzhen Li, Mechanisms of furfural reduction on metal electrodes: Distinguishing pathways for selective hydrogenation of bioderived oxygenates, Journal of the American Chemical Society, 2017, 139 (40), 14120-14128. DOI: 10.1021/jacs.7b06331
Yang Qiu, Le Xin, David Chadderdon, Ji Qi, Changhai Liang, Wenzhen Li, Integrated electrocatalytic processing of levulinic acid and formic acid to biofuel intermediate valeric acid, Green Chemistry, 2014, 30, 7893-7901. Full text PDF
Le Xin, Zhiyong Zhang, Ji Qi, David Chadderdon, Yang Qiu, Kayla Warsco, Wenzhen Li, Electricity storage in biofuels: Electrocatalytic conversion of levulinic acid to valeric acid and γ-valerolacetone, ChemSusChem, 2013, 6, 674-686. Full text PDF
Xiaotong Chadderdon, David Chadderdon, Tony Pfennig, Brent Shanks and Wenzhen Li*, Paired Electrocatalytic Hydrogenation and Oxidation of 5-(Hydroxymethyl)furfural for Efficient Production of Biomass-derived Monomers, Green Chemistry, 2019, DOI: 10.1039/C9GC02264C.
Paired Electrolysis of CO2 and Agricultural Waste/Residual Carbons for Higher-Valued Chemicals Production
CO2, the most notorious green-house gas (GHG), has been mass-produced from power plants, automobiles, and biogases. The electrocatalytic reduction of CO2 is a critical goal that could positively impact the global carbon balance by recycling CO2 into usable chemicals/fuels, thus attracting enormous research attention. Despite great breakthroughs in CO2 electro-reduction has been made in recent years, energy-efficient CO2 electro-reduction to selective production of targeted products (e.g. ethylene, formate, syngas) that can operate at low cell potentials (high energy efficiency) with high current density (high production rate) in a flow electrolysis mode remains a big challenge.
We are designing innovative flow electrolyzers for pairing electrocatalytic reduction of CO2 at the cathode, and oxidation of locally distributed, renewable/residual carbons (e.g. glycerol, furfural) at the anode for continuous production of targeted valuable chemicals at low temperature, ambient pressure and mild pH conditions. Our research goal is to develop earth-abundant metal catalysts for electro-reduction of CO2 and electro-oxidation of alcohol and aldehyde groups, optimize flow electrolyzer components and electrolytic conditions, and explore novel product separation methods, so as to design efficient paired electrolyzers for upgrading waste/residual carbons to valuable chemicals. We collaborate with Prof. Mark Mba-Wright on TEA and LCA studies of the paired flow electrolyzers.
Sponsors: USDA-NIFA, IEC Competitive Fund (2020)
Electrochemical Synthesis of Ammonia
Haber-Bosch ammonia synthesis is a mature industrial process, through which over 150 million tons of ammonia were produced per year for the fertilizer industry to support the large global population growth over the past century. However, this process consumes about 1.6% of all global energy output and emits ~1.5% of global CO2 (1.0% global GHG) emission. As an alternative, ammonia can be electrochemically synthesized directly from air and water without the need for harsh conditions (high temperature/pressure) and costly reactants such as high-purity hydrogen. Ammonia electrosynthesis has been proposed an innovative and transformative technology, which is fundamentally free of the problems of thermal synthesis, particularly considering its modular, flexible, and decentralized features. However, currently ammonia electrosynthesis has a very low Faradaic efficiency (electron efficiency, i.e. <5%), and production rate, (for example 10-9 molNH3 cm-2 electrode s-1). Great research breakthroughs in electrochemical materials and technologies may be used in electrosynthesis of ammonia.
We have developed a membrane-free approach based on the immiscibility of aqueous/organic electrolytes for lithium electro-deposition, which can be utilized for subsequent nitridation and ammonia synthesis. We found that a biphasic system of aqueous 1 M LiClO4 and 1 M LiClO4/propylene carbonate reinforced with PMMA (poly(methyl methacrylate)) acts the same as a LISICON-based aqueous/organic hybrid electrolyte system, but without any physical membrane. We did 15N2 experiment to confirm ammonia was synthesized from N2 and demonstrated a fairly high Faradaic efficiency (FE) of 57.2% and a production rate of 1.21 × 10−9 mol cm−2 s−1 for ammonia synthesis,
Our research is to verify ammonia is truly synthesized from N2 gas, not other N-impurities. With our collaboration with Prof. Shuang Gu (from Wichita State University) and Prof. Stuart Licht (from George Washington University), we recently found substantial levels of nitrate-N and nitrides-N unexpectedly existed in some commercial metal oxides (for example, 563±21ppm-N in Alfa Aesar-45007) and metallic irons (for example, 7,297±99ppm-N in Alfa Aesar-40337), respectively. We offered a simple two-step procedure (alkaline treatment for NOx− or acidic treatment for nitrides, followed by either HPLC or UV–vis analysis) as a reliable protocol for screening NOx−/nitrides impurities in catalyst materials. Our work was published in Nature Catalysis as an Analysis article. We wish our findings can serve the nitrogen-fixation community in a positive manner by raising awareness of the presence of high-level nitrogen-containing impurities in some commercial materials so as to avoid the misinterpretation (in the early research stage) of synthesized NH3 originating from N2 rather than from NOx −based impurities.
Sponsor: ARPAe-REFUEL (Subcontrats), IEC Cost-Share Funds (2017)
Kwiyong Kim, Yifu Chen, Jong-In Han, Hyung Chul Yoon, and Wenzhen Li*, Lithium-mediated Ammonia Synthesis from Water and Nitrogen: A Membrane-free Approach Enabled by Immiscible Aqueous/Organic Hybrid Electrolyte System, Green Chemistry, 2019, 21, 3839–3845, DOI: 10.1039/C9GC01338E.
Yifu Chen, Hengzhou Liu, Nguon Ha, Stuart Licht*, Shuang Gu,* Wenzhen Li*, Revealing Nitrogen-Containing Species in Commercial Catalysts Used for Ammonia Electrosynthesis, Analysis article, Nature Catalysis, 2020, 2020, 10.1038/s41929-020-00527-4.. Full article is here.
Electrochemical Reduction of Nitrate for Wastewater Treatment
The heavy use of nitrogen fertilizer has introduced significant reactive nitrogen (in particular nitrate) in water bodies (> 53% lost in fertilizer practice), which led to severe water pollution, such as eutrophication, hypoxia, and harmful algal blooms in estuarine and near-shore areas. Compared with heterogeneous catalysis, the electrochemical denitrification (nitrate reduction) process has several unique advantages, including: direct removal of nitrate to clean N2 gas (closing the nitrogen cycle) or hydroxylamine (a higher-valued chemical), no need of H2, low energy costs, readily integration with renewable wind energy, flexible and modular electrochemical reactors with low capital costs.
We are studying the fundamental mechanisms of electrocatalytic reduction of nitrate (and nitrite) to dinitrogen by combining experimental and DFT computation approaches (with collaboration with Prof. Luke Roling), and based on new understanding, to engineer the composition and structure nitrate reduction catalysts to close N-cycle, one of the top identified engineering challenges.
We are also interested in elucidating the similarities and differences between electrocatalytic reduction and heterogeneous catalytic reduction (by H2) of nitrate, and electrochemical upgrading of concentrated nitrate to higher-valued chemicals, such as hydroxylamine. Our collaborators are Prof. Shuang Gu in selective concentration of nitrate and Prof. Mark Mba-Wright in TEA and LCA studies of electrochemical upgrading of nitrate from waste streams.
Sponsor: NSF-CHE 2036944
Alkaline Hydrogen Oxidation and Evolution for Fuel Cells and Electrolyzers
Molecular hydrogen (H2) oxidation and evolution reactions (HOR/HER) are primary reactions associated with aqueous electrochemistry. HER and HOR find important uses not only in H2/O2 fuel cells and water electrolyzers, but also potentially in ammonia production and CO2 conversion electrolyzers, in which HOR may be coupled at the anode in cases where H2 sources are abundantly available. By switching from an acid electrolyte to alkaline electrolyte, the large overpotentials of oxygen reduction/evolution reaction (ORR/OER) - the long-time scientific challenge for fuel cells and electrolyzers - can be alleviated, however, the HER and HOR become sluggish in high pH electrolyte, thus more efficient HER/HOR electrocatalysts need to be explored.
Our group is investigating HOR over bimetallic electrocatalysts for alkaline electrolyte-based fuel cells and ammonia electrolyzers, towards the goal of understanding the relationship between composition and structure of bimetallic catalysts and their electrocatalytic activity by combining experimental and theoretical DFT studies.
We are passionate about understanding the similarities and differences between electrocatalytic hydrogenation (ECH) and heterogeneous catalytic reduction of small molecules, such as carbonyl group, CO2, NO3-, thus enabling advanced technologies for efficient energy conversion and distributed chemical manufacturing.
Yang Qiu, Le Xin, Yawei Li, Ian T McCrum, Fangmin Guo, Tao Ma, Yang Ren, Qi Liu, Lin Zhou, Shuang Gu, Michael J Janik, Wenzhen Li*, BCC-Phased PdCu Alloy as a Highly Active Electrocatalyst for Hydrogen Oxidation in Alkaline Electrolytes, Journal of the American Chemical Society, 2018, 140 (48), 16580-16588. DOI:10.1021/jacs.8b08356
Saline / Seawater Electrolyzers for H2 Production and Olefin Epoxidation
Storage of renewable energy is a major challenge in future energy system. Water electrolyzers that can split water into H2 and O2 (2H2O + electricity -> 2H2+O2) have attracted enormous attention as H2 being considered a long-term energy carrier (compared to renewable electrons stored in batteries). However, larger quantities of fresh water will likely become a bottleneck if hydrogen electrolyzers are widely deployed. In hot arid coastal regions where seawater and solar are readily available, it is very attractive to directly use sweater instead of high-purity water to generate H2, which is then supplied to a fuel cell system to co-produce electricity and fresh water. Despite great progress has been made in seawater electrolysis, splitting seawater faces chemical and engineering challenges. At the anode, the desired oxygen evolution reaction (OER, 4OH- -> O2 + 2H2O + 4e-, E0 = 1.23 V vs RHE) is competed by undesired chloride oxidation reactions, dominant by Cl2 evolution (ClER, 2Cl- -> Cl2, E0 = 1.36 V vs RHE). The design criteria for seawater electrolyzers need an anode potential of < 1.72 V vs RHE, and an alkaline electrolyte with pH>7.5 to avoid ClER. Materials of electrolyzer components need tolerate seawater corrosion.
We are investigating hydrogen evolution reaction (HER) cathode catalysts avoiding Mg(OH)2 deposition, Cl-tolerant oxygen evolution reaction (OER) anode catalysts, and rational design of seawater electrolyzer for H2 production. as well studying chlorine-mediated hydrocarbon transformations with natural seawater as the chlorine source.
We have been actively researching electrocatalysis, electrodes, and electrochemical devices for many years. Our past research projects include selective electrocatalytic oxidation of alcohols, direct alcohol fuel cells, direct carbohydrazide fuel cells, oxygen reduction and evolution reactions, photoelectrolysis of biorenewables, advanced catalytic materials, electrochemical processing of biorenewables, and they can be found in our published articles.
We gratefully acknowledge our current and previous sponsors: