Jingkun Li

East China University of Science and Technology

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Sanjeev Mukerjee

Universidad del Noreste

Qingying Jia

Chinese Academy of Medical Sciences & Peking Union Medical College

Frédéric Jaouen

Centre National pour la Recherche Scientifique et Technique (CNRST)

Li Jiao

East China University of Science and Technology

Ershuai Liu

Lawrence Berkeley National Laboratory

Moulay Tahar Sougrati

Réseau sur le Stockage Electrochimique de l'énergie

Andrea Zitolo

Synchrotron soleil

Shraboni Ghoshal

National Renewable Energy Laboratory

Zipeng Zhao

University of California, Los Angeles

Deborah J. Myers

Argonne National Laboratory

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East China University of Science and Technology

Northeastern University

Chinese Academy of Sciences

Centre National de la Recherche Scientifique

Universidad del Noreste

Tianjin University

State Key Laboratory of Chemical Engineering

Soochow University

University of Science and Technology of China

Collaborative Innovation Center of Chemical Science and Engineering Tianjin

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Chemical Vapor Deposition of Fe-N-C Oxygen Reduction Catalysts with Full Utilization of Dense Fe-N4 Sites

Li Jiao Jingkun Li Lynne K. LaRochelle Qiang Sun Thomas Stracensky

Replacing scarce and expensive platinum (Pt) with metal-nitrogen-carbon (M-N-C) catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) has largely been impeded by the low activity of M-N-C, in turn limited by low site density and low site utilization. Herein, we overcome these limits by implementing chemical vapor deposition (CVD) to synthesize Fe-N-C, an approach fundamentally different from previous routes. The Fe-N-C catalyst, prepared by flowing iron chloride vapor above a N-C substrate at 750 ℃, has a record Fe-N 4 site density of 2×10 20 sites·gram -1 with 100% site utilization. A combination of characterizations shows that the Fe-N 4 sites formed via CVD are located exclusively on the outer-surface, accessible by air, and electrochemically active. This catalyst delivers an unprecedented current density of 33 mA·cm -2 at 0.90 V i R-free ( iR -corrected) in an H 2 -O 2 PEMFC at 1.0 bar and 80 ℃.

Carbon fibers

10.26434/chemrxiv.12918983.v1

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Suppression of current-induced membrane discharge of bipolar membranes by regulating ion crossover transport

Journal of Energy Chemistry (2024)

Tingting Yu Haolan Tao Jingkun Li Cheng Lian Honglai Liu

10.1016/j.jechem.2024.05.011

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(Invited) Current Understandings of the Slow Kinetics of the Hydrogen Evolution Reaction in Alkaline Media

Meeting abstracts/Meeting abstracts (Electrochemical Society. CD-ROM) (2018)

Sanjeev Mukerjee Jingkun Li Qingying Jia

Efficient generation of H 2 as a clean energy source from water constitutes one of the cornerstones of the so-called hydrogen economy. We are currently limited to precious metal such as Pt as effective HER catalysts in acid owing to the stability issue, but also in alkaline owing to the slow kinetics of HER in high pH environment. The origin of the slow HER rate in alkaline, and how to overcome this fundamental limitation have been under extensive debatable. By far there are three schools of thoughts led by Markovic, Gasteiger, and Koper, and their respective collaborators, although they all agree that the HER kinetics in alkaline is limited by the Volmer step M + H 2 O + eˉ ↔ M-H ads + OHˉ. Markovic et al . 1 stated that and the reactive hydroxyl species ( OH ads ) accomondated by the surface oxophilic sites is responsible for the acceleration of this step. We recently provided the first experimental evidence of OH ads accommodated by the Ru in both Pt-Ru and Ru systems within the HER/HOR potential region, and its promoting role on the HER/HOR kinetics in alkaline media. 2 Gasteiger et al. 3 and Yushan () argued that H-binding energy ( M-H ) is the sole descriptor for the HER rate in a broad range of pH environments, although the origin of the difference in H-binding energy is not clear. Most recently, Koper’s group 4 proposed a model that states a possible pH dependence of surface water ( H 2 O ) orientation and highlights the role of the reorganization of interfacial water for the HER kinetics to accommodate charge transfer through the electric double layer. In this talk, all the three mechanisms will be discussed in the context of new experimental and computational results achieved by us and others to update our understanding of the HER kinetics in alkaline pH. Acknowledgements : The authors gratefully acknowledge the financial support of the Department of Energy (DOE) via Energy Efficiency and Renewable Energy (EERE), under the auspices of an incubator effort lead by Proton On-Site and a new grant (grant #.. ) under the HydroGen initiative. Authors also acknowledge the support from arpa.e under their open initiative via a grant lead by Pajarito Powders, Albuquerque (grant # ). The support from (DOE) office of science under contract no DE-SC0012704 for building and maintaining the National Synchrotron Light Source-II (NSLS-II) at Brookhaven National Laboratory (BNL), Upton, NY and Thermo Fisher for instrumental support is gratefully acknowledged. References (1) Subbaraman, R.; Tripkovic, D.; Chang, K.-C.; Strmcnik, D.; Paulikas, A. P.; Hirunsit, P.; Chan, M.; Greeley, J.; Stamenkovic, V.; Markovic, N. M. Nat. Mater. 2012 , 11 , 550. (2) Li, J.; Ghoshal, S.; Bates, M. K.; Miller, T. E.; Davies, V.; Stavitski, E.; Attenkofer, K.; Mukerjee, S.; Ma, Z.-F.; Jia, Q. Angew. Chem. Int. Ed. , n/a. (3) Durst, J.; Siebel, A.; Simon, C.; Hasche, F.; Herranz, J.; Gasteiger, H. A. Energy Environ. Sci. 2014 , 7 , 2255. (4) Ledezma-Yanez, I.; Wallace, W. D. Z.; Sebastián-Pascual, P.; Climent, V.; Feliu, J. M.; Koper, M. T. M. Nat. Energy 2017 , 2 , 17031.

10.1149/ma2018-01/29/1703

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Operando characterization techniques for electrocatalysis

Energy & Environmental Science (2020)

Jingkun Li Jinlong Gong

Significant progress toward the understanding of the electrochemical process has been achieved in the past decades, owning to the advancements in operando characterization techniques.

Characterization

10.1039/d0ee01706j

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Citations (189)

Low-Valence Mg²⁺ Doping Suppresses Irreversible Phase Transition of Sodium-Rich Fluorophosphate upon Additional Na⁺ Deintercalation

ACS Applied Energy Materials (2025)

Ke-Jing Ren J. J. Qiu Honglai Liu Hongfang Song Quan Li

10.1021/acsaem.4c03216

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Evolution Pathway from Iron Compounds to Fe₁(II)–N₄ Sites through Gas-Phase Iron during Pyrolysis

Journal of the American Chemical Society (2019)

Jingkun Li Li Jiao Evan C. Wegener Lynne K. LaRochelle Ershuai Liu

Pyrolysis is indispensable for synthesizing highly active Fe–N–C catalysts for the oxygen reduction reaction (ORR) in acid, but how Fe, N, and C precursors transform to ORR-active sites during pyrolysis remains unclear. This knowledge gap obscures the connections between the input precursors and the output products, clouding the pathway toward Fe–N–C catalyst improvement. Herein, we unravel the evolution pathway of precursors to ORR-active catalyst comprised exclusively of single-atom Fe1(II)–N4 sites via in-temperature X-ray absorption spectroscopy. The Fe precursor transforms to Fe oxides below 300 °C and then to tetrahedral Fe1(II)–O4 via a crystal-to-melt-like transformation below 600 °C. The Fe1(II)–O4 releases a single Fe atom that diffuses into the N-doped carbon defect forming Fe1(II)–N4 above 600 °C. This vapor-phase single Fe atom transport mechanism is verified by synthesizing Fe1(II)–N4 sites via "noncontact pyrolysis" wherein the Fe precursor is not in physical contact with the N and C precursors during pyrolysis.

10.1021/jacs.9b11197

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Citations (228)

Controllable Cu⁰‐Cu⁺ Sites for Electrocatalytic Reduction of Carbon Dioxide

Angewandte Chemie International Edition (2021)

Xintong Yuan Sai Chen Dongfang Cheng Lulu Li Wenjin Zhu

Abstract Cu‐based electrocatalysts facilitate CO 2 electrochemical reduction (CO 2 ER) to produce multi‐carbon products. However, the roles of Cu 0 and Cu + and the mechanistic understanding remain elusive. This paper describes the controllable construction of Cu 0 ‐Cu + sites derived from the well‐dispersed cupric oxide particles supported on copper phyllosilicate lamella to enhance CO 2 ER performance. 20 % Cu/CuSiO 3 shows the superior CO 2 ER performance with 51.8 % C 2 H 4 Faraday efficiency at −1.1 V vs reversible hydrogen electrode during the 6 hour test. In situ attenuated total reflection infrared spectra and density functional theory (DFT) calculations were employed to elucidate the reaction mechanism. The enhancement in CO 2 ER activity is mainly attributed to the synergism of Cu 0 ‐Cu + pairs: Cu 0 activates CO 2 and facilitates the following electron transfers; Cu + strengthens *CO adsorption to further boost C−C coupling. We provide a strategy to rationally design Cu‐based catalysts with viable valence states to boost CO 2 ER.

Reversible hydrogen electrode

10.1002/anie.202105118

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Citations (251)

Unifying the Alkaline Hydrogen Evolution/oxidation Reactions Kinetics by Identifying the Roles of Hydroxyl-Water-Cation Adducts

Ershuai Liu Jingkun Li Li Jiao Huong Thi Thanh Doan Zeyan Liu

Despite the fundamental and practical significance of the hydrogen evolution and oxidation reactions (HER/HOR), their kinetics in base remain unclear. Herein, we show that the alkaline HER/HOR kinetics can be unified by the catalytic roles of the adsorbed hydroxyl (OHad)-water-alkali metal cation (AM+) adducts, on the basis of the observations that enriching the OHad abundance via surface Ni benefits the HER/HOR; increasing the AM+ concentration only promotes the HER while varying the identity of AM+ affects both HER/HOR. The presence of OHad-(H2O)x-AM+ in the double layer region facilitates the OHad removal into the bulk forming OH--(H2O)x-AM+ as per the hard-soft acid-base (HSAB) theory, thereby selectively promoting the HER. It can be detrimental to the HOR as per the bifunctional mechanism as the AM+ destabilizes the OHad, which is further supported by the CO oxidation results. This new notion may be important for alkaline electrochemistry.

10.26434/chemrxiv.7137026

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Mechanistic insights into pH-dependent hydrogen electrocatalysis by flipping interfacial water

Qiang Sun Nicholas Oliveira Sergiy Tyukhtenko Jason J. Guo Nathalie Myrthil

A grand challenge in electrochemistry is to understand and promote electrochemical processes by exploring and exploiting the interface. Herein, we promoted the hydrogen evolution and oxidation reactions (HER/HOR) of platinum in base by employing N-methylimidazoles to reorientate interfacial water against the interfacial electric field as evidenced by in situ spectroscopic characterization of the interface. We accordingly established a unified mechanism by which the HER/HOR in acid and base proceeds via diffusion of proton and hydroxide, respectively, through interface via interfacial water by the Grotthuss mechanism. This mechanism accounts for the pH-dependent HER/HOR kinetics of platinum, a long-standing puzzle. Furthermore, we demonstrated 40% performance improvement of an anion exchange membrane electrolyzer by adding 1,2-dimethylimidazole into the alkaline solution fed into its Pt cathode.

Electrolysis of water

10.33774/chemrxiv-2021-gks2k

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Citations (2)

Unifying the Hydrogen Evolution and Oxidation Reactions Kinetics in Base by Identifying the Catalytic Roles of Hydroxyl-Water-Cation Adducts

Journal of the American Chemical Society (2019)

Ershuai Liu Jingkun Li Li Jiao Huong Thi Thanh Doan Zeyan Liu

Despite the fundamental and practical significance of the hydrogen evolution and oxidation reactions (HER/HOR), their kinetics in base remain unclear. Herein, we show that the alkaline HER/HOR kinetics can be unified by the catalytic roles of the adsorbed hydroxyl (OHad)-water-alkali metal cation (AM+) adducts, on the basis of the observations that enriching the OHad abundance via surface Ni benefits the HER/HOR; increasing the AM+ concentration only promotes the HER, while varying the identity of AM+ affects both HER/HOR. The presence of OHad-(H2O)x-AM+ in the double-layer region facilitates the OHad removal into the bulk, forming OH–-(H2O)x-AM+ as per the hard–soft acid–base theory, thereby selectively promoting the HER. It can be detrimental to the HOR as per the bifunctional mechanism, as the AM+ destabilizes the OHad, which is further supported by the CO oxidation results. This new notion may be important for alkaline electrochemistry.

Base (topology)

10.1021/jacs.8b13228

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Citations (285)