Di-Jia Liu

Proton exchange membrane water electrolyzer (PEMWE) holds a promise for large‐scale and highly efficient hydrogen production through electrocatalytic water splitting. Its widespread commercial adoption, however, is hindered by its reliance on expensive and scarce platinum group metals (PGMs) as the electrode catalyst materials. This is particularly the case at the PEMWE anode where the costly iridium is required to promote oxygen evolution reaction (OER). This article provides a brief review of the recent progresses and challenges in searching for PGM‐free OER catalysts as the low‐cost replacement of PGM catalysts, as well as our perspectives on future research directions from rational catalyst design to their potential industrial deployment.

Electrochemical carbon dioxide reduction reaction (eCO ₂ RR) provides a pathway to convert CO ₂ into value‐added chemicals. Here, we report a family of carbon‐supported tin–copper (Sn–Cu) bimetallic catalysts synthesized via an amalgamated lithium metal (ALM) method with controlled tuning of metal dispersion from isolated atoms to nanocrystallites. As metal loadings increase, the catalyst structure evolves from atomically dispersed Sn‐Cu dual sites (Sn _1.5 Cu/C‐0.75) to Sn‐rich nanodomains (Sn ₃ Cu/C‐13) and Cu/Sn crystallites (Sn ₃ Cu/C‐24), leading to a systematic shift in CO ₂ RR selectivity from acetaldehyde to formate at low overpotentials. Notably, Sn _1.5 Cu/C‐0.75 achieves a Faradaic efficiency of 49.7% for acetaldehyde at −0.5 V versus the reversible hydrogen electrode. The CO ₂ conversion pathways behind these selective, size‐modulated catalysts are elucidated by structural characterization, together with electrochemical analysis of structure‐selectivity correlations, establishing a clear structure‐property relationship for tuning CO ₂ RR pathways.

The overpotential in multielectron transfer heterogeneous electrocatalysis fundamentally arises from thermodynamic and kinetic disparities among elementary steps; however, deciphering coupled and competing steps has long remained a challenge. Here, we establish an electrochemical deconvolution paradigm based on key processes in electrocatalytic reactions, such as charge accumulation, electron/proton transfer, and intermediate evolution, to resolve competing elementary steps. Taking the oxygen evolution reaction as a prototypical reaction, we design a model catalyst featuring a precise isolated cation-anion vacancy pair and track the previously elusive electrochemical behavior of lattice oxygen by disentangling interference from adsorbed oxygen intermediates. Mechanistically, the lattice oxygen oxidation pathway originates from the spontaneous, nonelectrochemical deprotonation of replenished water molecules coordinated to unsaturated cation sites. Alternating current techniques further reveal that although lattice oxygen oxidation requires a higher potential than metal oxidation, it exhibits faster kinetics, providing insight into its superior catalytic activity. These findings establish a direct experimental correlation between the initial chemical state and the catalytic activity and prove surface-confined lattice oxygen cycling. Furthermore, expanding conventional potential-current analysis into a multidimensional framework enables disentanglement of thermodynamic and kinetic contributions of key elementary steps, thereby guiding the rational optimization of various complex multielectron transfer reactions.

We report an electrochemical CO₂ reduction reaction catalyzed by a paramagnetic and conductive CuO/Cu interface with spins polarized by a moderate external magnetic field (MF) of ∼800 gauss, achieving a ∼30% increase in CO₂-to-C₂₊ Faradaic efficiency (FE) compared to that in the absence of the MF in a flow cell electrolyzer. At a current density of 400 mA/cm², the CO₂-to-C₂₊ FE reached 86.7 ± 2.7% with 47.9 ± 1.4% cathodic energy efficiency (EE) in contrast to the CO₂-to-C₂₊ FE of 67.6% with 36.4% of EE in the absence of MF. Notably, ethanol production exhibits a much higher response to the MF (∼55.6% increase in FE) than ethylene (∼6.4% increase in FE) at 400 mA/cm². In situ surface-enhanced Raman spectroscopy (SERS) captured magnetic-field-enhanced *CO coverage and ethanol-forming C₂ intermediates on CuO/Cu, providing direct spectroscopic evidence of spin-modulated pathway selection. Computational study suggests that the enhancement of ethanol selectivity is due to the reduced reaction kinetic barrier under MF, while the ethylene selectivity is less affected, mainly due to the insensitivity of the kinetic barriers under MF.

Large-scale battery manufacturing requires understanding the fundamental principles of materials and interfaces and relies on advanced techniques for detailed interrogation. Despite advancements in the industrial scale production and their associated quality control tools, challenges such as electrode heterogeneity, internal defects, and large-scale material waste (e.g., scrap) can hamper manufacturing. Synchrotron X-ray characterization techniques offer spatial, temporal, and chemical resolution that can provide diagnostic insights for metrology across various manufacturing steps. This review examines the use of synchrotron tools to advance understanding of key steps in the battery manufacturing process. Recent examples demonstrate how synchrotron methods resolve manufacturing challenges and uncover degradation pathways that are otherwise inaccessible. Future directions for advancing battery manufacturing emphasize collaboration between academia and industry through the use of synchrotron X-ray techniques.

As the global demand for energy storage grows, rechargeable aqueous batteries have gained attention as a promising candidate, offering intrinsic safety, environmental sustainability, and low manufacturing costs. For aqueous batteries key challenge lies in the narrow electrochemical stability window which restricts output voltage and energy. Pure water has a narrow electrochemical stability window of 1.23 V, constrained by hydrogen and oxygen evolution (HER/OER). However, kinetic barriers induce polarization, expanding the operational voltage. Since OER faces higher kinetic barriers than HER, metal anodes with high HER overpotentials are crucial to suppress HER and enhance battery performance. ¹ The sp metals are good candidates for aqueous batteries due to their intrinsic high HER overpotential. The ΔG _H* of sp metal is high because their d band lies low that it plays no role in the bonding of hydrogen, and the sp band at Fermi level does not overlap with H 1s orbital effectively. Tin (Sn) as a typical sp metal, has recently emerged as a promising anode due to its unique electrochemical properties, including high acid tolerance, good recyclability, and the ability to undergo multivalent redox reactions. ² Unlike Zn, Sn features a body-centered tetragonal crystal structure with isotropic surface energy, reducing the risk of dendrite formation. However, significant challenges remain, including the formation of inactive ‘dead Sn’ and competitive HER, which accelerate electrolyte consumption and capacity decay. Recent advancements in electrolyte and interfacial engineering have demonstrated progress in mitigating these issues, yet further optimization is required to unlock the full potential of Sn. ^3-4 We will provide a comprehensive review of Sn metal batteries, highlight remaining challenges and future opportunities for Sn metal anodes in both acidic and alkaline environments, and discuss some of our typical works in this emerging field. ACKNOWLEDGEMENT This work was supported by the Energy Storage Research Alliance “ESRA” (DE-AC02-06CH11357), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. The idea is conceived during the ESRA preparation period. D.-J.L. and H.Z.Z. acknowledges the funding support from the Joint Task Force Initiative (JTFI) at the University of Chicago (2-84889-4401). Y.S.M., D.-J.L., and K.X. acknowledges the support from the Energy Transition Network at the University of Chicago. References H. Zhang, D.-J. Liu, K. Xu, Y. S. Meng. Adv. Mater. 2025 , 2417757. H. Zhang, D. Xu, F. Yang, J. Xie, Q. Liu, D. Liu, M. Zhang, X. Lu, Y. S. Meng. Joule 2023 , 7 , 971-985. J. Wang, S. K. Catalina, Z. Jiang, X. Xu, Q. T. Zhou, W. C. Chueh, J. T. Mefford, Joule 2024 , 8, 3386-3396 T. Xiao, L. Liu, H. Liu, T. Li, D. Cai, W. S. Lew, Y. Zhang, H. Bao, J.-L. Yang, H. J. Fan, Joule 2025 . 9, 101820.

Carbon-supported single-atom catalysts exhibit outstanding performance and broad application potential in electrocatalytic CO ₂ reduction reactions (CO ₂ RR). ^[1,2] Identifying the CO ₂ RR reaction intermediates during electrocatalysis could improve our understanding on the catalytic mechanism for better design of more efficient catalysts. in-situ Raman spectroscopy could detect the transient intermediate over the catalyst surface under the reaction condition, therefore serving as important tool in revealing CO ₂ RR reaction pathways. However, conventional in-situ Raman spectroscopy faces significant challenges in effectively detecting key reaction intermediates and structural evolution at catalytic active sites over carbon supported catalyst due to the intense fluorescence background, strong optical absorption of carbon materials, and the extremely weak Raman signals from single-atom active sites. To overcome these limitations, we employed Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) ^[3] , which significantly enhances Raman signals through electromagnetic field enhancement by plasmonic nanoparticles coated with an inert shell. Using SHINERS, we successfully monitored the catalytic reaction intermediates of Cu single-atom catalysts supported on carbon substrates with different morphologies during CO ₂ RR. Our results revealed distinctly different CO ₂ RR reaction pathways mediated by atomic-scale dispersed Cu active sites on carbon supports of varying morphologies, highlighting the critical role of substrate structure in influencing catalytic pathways. Additionally, we extended the application of SHINERS to successfully observe the catalytic processes of differently sized Sn nanoparticles and their oxides supported on carbon substrates, effectively identifying essential reaction intermediates and their structural transformations. This study confirms SHINERS as a powerful analytical technique, providing deep insights into the catalytic mechanisms of single-atom and nanoscale catalysts, thus promoting the rational design and development of advanced catalysts for CO ₂ reduction. ACKNOWLEDGMENT The work performed by JW and D.L. were partially supported by Laboratory Directed Research and Development (LDRD) funding from Argonne National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357. J.W. and D.L were also supported by Joint Task Force Initiative of University of Chicago. [1]. Xu, H.; Rebollar, D.; He, H.; Chong, L.; Liu, Y.; Liu, C.; Sun, C.-J.; Li, T.; Muntean, J. V.; Winans, R. E.; Liu, D.-J.; Xu, T. Highly Selective Electrocatalytic CO₂ Reduction to Ethanol by Metallic Clusters Dynamically Formed from Atomically Dispersed Copper. Nat. Energy 2020 , 5 (8), 623–632. [2]. Xu, H.; Wang, J.; He, H.; Hwang, I.; Liu, Y.; Sun, C.; Zhang, H.; Li, T.; Muntean, J. V.; Xu, T.; Liu, D.-J. Modulating CO₂ Electrocatalytic Conversion to the Organics Pathway by the Catalytic Site Dimension. J. Am. Chem. Soc . 2024 , 146 (15), 10357–10366. [3]. Li, J.-F.; Huang, Y.-F.; Ding, Y.; Yang, Z.-L.; Li, S.-B.; Zhou, X.-S.; Fan, F.-R.; Zhang, W.; Zhou, Z.-Y.; Wu, D.-Y.; Ren, B.; Wang, Z.-L.; Tian, Z.-Q. Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy. Nature 2010 , 464 (7287), 392–395.

C ₂₊ molecules, such as ethylene and ethanol, are widely produced by the chemical industry for applications in plastics, chemicals, fuels, and other sectors. The electrochemical reduction of CO ₂ (eCO ₂ RR) to C ₂₊ chemicals has attracted significant attention as it offers a promising alternative route for their production directly from CO ₂ . Despite significant progress in catalyst development, challenges remain in improving selectivity, activity, and long-term stability. Furthermore, the gap between laboratory-scale success and industrial application remains a key hurdle for commercialization. A deeper understanding of catalyst behavior, system design, and industrial advancements is essential for bridging the gap between fundamental research and practical implementation and scaling up eCO ₂ RR technologies In this work, we present a comprehensive study including (1) the design and optimization of Cu-based catalyst and electrolyzer system for enhanced C ₂₊ chemicals production, and (2) a detailed assessment of state-of-the-art eCO ₂ RR technologies from both literature and industrial perspectives. For the experimental aspect, among all possible materials, Cu remains the most widely studied catalyst for the electrochemical reduction of CO ₂ to C ₂₊ products, renowned for its unique ability to facilitate multi-carbon product formation. ¹ Our study integrates the modifications of sputtered Cu-based catalyst with the optimization of CO ₂ electrolyzer system, achieving high performance at industrially relevant current densities (> 100 mA/cm ² ). Beyond experimental development, we analyze the current landscape of eCO ₂ RR technologies by systematically reviewing literature on catalyst development, microenvironment control, and mechanistic understanding. ² Additionally, we assess industrial progress through patent trends, emerging scale-up efforts, and key industry players. While recent years have seen exponential growth in industrial activity, as reflected by the rising number of patents, commercialized examples remain scarce, with most efforts concentrated in startups or newly formed business divisions. The combination of two-level assessment also helps us identify specific technological gaps and outline potential pathways for advancing eCO ₂ RR toward commercialization. By integrating experimental data with a broad technological evaluation, this study provides critical insights into the current development stage, key challenges, and future opportunities on advancing eCO ₂ RR toward practical applications in chemical manufacturing. REFERENCES (1) Bagger, A.; Ju, W.; Varela, A. S.; Strasser, P.; Rossmeisl, J. Electrochemical CO ₂ Reduction: A Classification Problem. ChemPhysChem 2017 , 18 , 3266-3273. (2) Guo, S.; Wang, J.; Zhang, H.; Iloeje, C. O.; Liu, D.-J. Direct Electrochemical Reduction of CO ₂ to C ₂₊ Chemicals: Catalysts, Microenvironments, and Mechanistic Understanding. ACS Energy Lett. 2025 , 10 , 600-619.

Production of valuable chemicals via electrochemical CO ₂ reduction (eCO ₂ RR) is promising research area from both fundamental science and application aspects. While eCO ₂ RR has been demonstrated to produce C ₁ (e.g., CO, formic acid), and to a lesser degree, C ₂ (e.g., ethylene, ethanol) products with good efficiency and selectivity, the controlled formation of C ₃ products remains challenging. Multi-carbon compound formation through eCO ₂ RR requires multiple electrochemical steps including CO ₂ activation, C–C coupling, and hydrogenation. Uncontrolled side reactions hinder selectivity, leading to undesired byproducts such as methane or hydrogen and overall reduction of Faradaic efficiency. Copper-based catalysts are the most promising for muti-carbon product formation due to their ability to facilitate C–C coupling. However, traditional copper-based catalysts often struggle with low selectivity and efficiency for C ₃ product formation due to complex reaction pathways and competing side reactions. Here we will introduce our recent study on eCO ₂ RR to C ₃ alcohols, with demonstrated Faradic efficiency up to 90%. These advances highlight the critical importance in control catalyst morphology and micro-environment for efficient electrochemical conversion of CO₂ into valuable long-chain chemicals. ACKNOWLEDGMENT This study is supported by Laboratory Directed Research and Development (LDRD) funding from Argonne National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357. References S Guo, J Wang, H Zhang, CO Iloeje, D.-J. Liu. ACS Energy Lett. 2025 , 10 , 600-619. H. Xu, D. Rebollar, H. He, L. Chong, Y. Liu, C. Liu, C.-J. Sun, T. Li, J. V. Muntean, R. E. Winans, D.-J. Liu, T. Xu. Nat. Energy 2020 , 5 , 623-632. H. Xu, J. Wang, H. He, I. Hwang, Y. Liu, C. Sun, H. Zhang, T. Li, J. V. Muntean, T. Xu, D.-J. Liu. J. Am. Chem. Soc. 2024 , 146 , 10357-10366.

The selectivity of electrocatalytic CO₂ reduction reaction (eCO₂RR) under nanoconfinement was investigated over catalysts of single-atom copper supported by three commercial carbons of varying microporosities. We found that the microporosity of the carbon support can significantly promote the selectivity of eCO₂RR toward the formation of glycerol (C₃H₈O₃), achieving a Faradaic efficiency (FE) of 90.3% at −0.7 V vs. RHE. The support’s microporosity influences profoundly on CO₂ adsorption, Cu active site electronic and ligation structures, eCO₂RR reaction pathways and product selectivity, observed experimentally by synchrotron x-ray absorption and in situ Raman spectroscopy. This study revealed the importance of nanoconfinement as a critical designing dimension in future electrocatalyst for highly selective CO₂ conversion to multi-carbon chemicals.