About

Yiguang Ju is the Robert Porter Patterson Professor in the Department of Mechanical and Aerospace Engineering at Princeton University. He serves as the Director of the DOE Energy Earthshot Research Center (EERC) for Hydrogen Production and is the Head of Electro-manufacturing Science. Additionally, he is an associated faculty member at the Princeton Plasma Physics Laboratory (PPPL). Professor Ju is a co-founder of several companies including HiTNano Inc, Princeton NuEnergy Inc, Polymer-X Inc, and USPlasma Inc. He is also the founding president of the Asian American Academy of Science and Engineering (AAASE). His research encompasses combustion, plasma catalysis, laser diagnostics, combustion kinetics, plasma-assisted combustion, ammonia synthesis, high pressure combustion involving hydrogen and ammonia, non-equilibrium chemical kinetics and synthesis, plasma physics and diagnostics, ferroelectric materials, multiscale modeling, and machine learning. Professor Ju's work integrates experimental and theoretical approaches to advance understanding and innovation in combustion and low carbon energy conversion technologies.

Research topics

• Chemistry
• Materials science
• Thermodynamics
• Organic chemistry
• Chemical engineering
• Composite material
• Polymer chemistry
• Physics
• Mechanics
• Physical chemistry
• Engineering
• Environmental science
• Nanotechnology
• Nuclear engineering

Selected publications

• Flame dynamics and kinetic coupling of ammonia and dimethyl-ether in non-premixed cool and warm flames at elevated pressure

  Combustion and Flame · 2026-02-14

  articleSenior author
  PublisherDOI

• Three-beam hybrid fs/ps coherent anti-Stokes Raman scattering of rotation–vibration non-equilibrium

  Optics Letters · 2026-03-25

  articleSenior author

  We demonstrate time-resolved rotational and vibrational temperature measurements to probe plasma non-equilibrium through a simple three-beam hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) system. A single pump/Stokes pair is employed to generate both the pure-rotational and ro-vibrational Raman coherence. A novel phase-matching scheme, to our knowledge, is employed to spatially overlap the two CARS signals, simplifying the optical design and allowing signal selection by tuning a single spectrometer grating. Measurements were performed near the electrodes in a N 2 DC glow discharge. Both the rotational temperature and the vibrational populations up to v =8 were calculated from the separately measured single-shot pure-rotational and ro-vibrational CARS spectra. Strong rotation–vibration non-equilibrium was observed at both electrodes, with the cathode showing higher vibrational and rotational temperatures. In addition, non-Boltzmann behaviors were observed at both electrodes. This simplified approach enables measurements of rotational and vibrational temperatures with high spatial resolution in non-equilibrium flows.

  PublisherDOI

• Supplementary document for Single-shot three-beam hybrid fs/ps coherent anti-Stokes Raman scattering of strong rotation-vibration non-equilibrium - 7840945.pdf

  Figshare · 2026-04-09

  articleOpen accessSenior author

  Supplemental information

  PublisherDOI

• Hybrid fs/ps CARS Characterization of Rotational and Vibrational Excitation of N ₂ in RF Non-Equilibrium Plasma

  2026-01-08

  articleSenior author

  This manuscript presents spatially resolved measurements of vibrational and rotational excitation in intermediate pressure (20~Torr) N2 plasmas sustained in a radio-frequency (RF) dielectric barrier discharge (DBD) reactor, using a three-beam hybrid femtosecond/picosecond (fs/ps) coherent anti-Stokes Raman scattering (CARS) diagnostic technique. The measurements span RF input powers from 20 to 55~W and include vertical spatial scans across the 4~mm interelectrode gap with a 0.5~mm step size. Notably, we report the experimental observation of vibrational levels up to v = 6 in a pure N2 RF-DBD plasma at 20~Torr. With increasing power, the vibrational temperature rises sharply and then plateaus at higher power inputs, indicating a transition to a regime dominated by enhanced V–T relaxation and dissociation from highly excited vibrational states. Spatially, the vibrational temperature profiles peak near the center of the reactor and decrease toward both electrodes, with a mild asymmetry likely arising from geometric differences between the electrodes and the corresponding sheath dynamics. These results confirm that vibrational excitation in RF-DBD plasmas is structured and non-uniform, despite the discharge’s visually diffuse appearance in optical emission.

  PublisherDOI

• Supplementary document for Single-shot three-beam hybrid fs/ps coherent anti-Stokes Raman scattering of strong rotation-vibration non-equilibrium - 7840945.pdf

  Figshare · 2026-04-09

  articleOpen accessSenior author

  Supplemental information

  PublisherDOI

• Unraveling In-Situ Formation of Surface Nickel Nitride Structures in Plasma-Assisted Catalytic Ammonia Synthesis

  The Journal of Physical Chemistry Letters · 2026-02-17

  articleOpen accessSenior authorCorresponding

  We report the in situ formation of Ni nitride for plasma-assisted ammonia synthesis. Both the surface nitrogen concentration and the ammonia formation rate exhibit dependence on the N2:H2 feed ratio. The maximum surface nitrogen concentration occurs at a N2:H2 ratio of 4:1, and the maximum catalytic activity occurs at 2:1. In contrast, the formation of gas phase radicals is less sensitive to feed composition, indicating that Ni nitride is more kinetically relevant to ammonia production than gas-phase radicals. The plasma-induced formation of Ni nitride is therefore proposed to be a critical contributor to the synergistic effects in plasma-assisted catalytic ammonia synthesis. Additionally, Ni nitride alters the surface reaction mechanism of plasma-assisted ammonia synthesis, with the rate-determining-step (RDS) shifting to surface-bound NH3 formation rather than N2 activation at temperatures below 373 K. These findings provide mechanistic insight that opens opportunities for optimizing the performance of plasma-assisted catalytic ammonia synthesis.

  PublisherDOI

• <i>Ab Initio</i> -Trained Machine Learning Molecular Dynamics Model for Radical Reactions in Hydrogen Combustion

  2026-01-08

  articleSenior author

  Machine learning-based molecular dynamics (ML-MD) has emerged as a powerful tool that bridges the accuracy of quantum mechanical methods with the efficiency of classical molecular dynamics. However, existing ML-MD models often fall short in accurately predicting individual reaction rates due to incomplete sampling of reaction pathways and the absence of a multifidelity framework that combines data of varying precision. In this work, we develop and validate integrated ab initio-trained ML-MD (aML-MD) models for two key radical reactions in hydrogen combustion: H + HO2 → H2 + O2 and O + HO2 → O2 + OH. Using the DeePMD-kit framework, we first construct an aML-MD model trained solely on high-accuracy ab initio data and demonstrate its ability to predict individual reaction rates across distinct pathways via quasi-classical trajectory (QCT) calculations with excellent agreement to PES-based results. We then apply transfer learning to build another aML-MD model that incorporates a large set of moderate-accuracy DFT/PES data and a small subset of ab initio data. This multifidelity approach reduces computational cost by over fivefold while maintaining predictive accuracy within 20% of PES-based benchmarks. Further NEB simulations indicate that transfer learning yields a more accurate reaction barrier, thereby enhancing the model’s fidelity in capturing the underlying reaction dynamics. The results demonstrate the effectiveness of combining multifidelity data and transfer learning to enable general-purpose ML-MD models capable of accurately capturing complex reaction dynamics, with promising applications to larger, multi-reaction chemical systems.

  PublisherDOI

• Oxidation of Ammonia Blends with Methyl Formate in a Supercritical Pressure Jet-Stirred Reactor up to 100 atm

  2026-01-08

  articleSenior author

  Ammonia (NH3) is a carbon-free fuel with strong potential for low-emission combustion systems, but its low reactivity limits practical application. Blending NH3 with oxygenated fuels offers a promising strategy to enhance ignition and oxidation characteristics while influencing NOx formation pathways. In this work, the oxidation of NH3/CH3OCHO(MF)/O2/N2 mixtures is studied in the Princeton supercritical-pressure jet-stirred reactor (SP-JSR) at 100 atm over 350–950 K under fuel-lean and fuel-rich conditions. Quantitative measurements of major species and intermediates are obtained, and a high-pressure kinetic mechanism (HP-Mech) is developed by integrating updated MF oxidation kinetics, NH3 sub-mechanisms, and newly introduced MF/NH3 coupling reactions. The updated mechanism accurately captures NH3 consumption trends and key intermediate profiles, outperforming existing models under ultra-high-pressure conditions. Path-flux analysis shows that MF oxidation is dominated by OH-initiated H-abstraction, while MF/NH3 interactions mainly occur through MF/NO2/NH2 coupling. OH sensitivity analysis at 800 K further confirms the dominant role of CH3OCHO + NO2 in sustaining OH and NOx. Overall, the results provide the first detailed experimental and kinetic study of NH3/MF oxidation at ultra-high pressure and clarify the mechanistic basis for how oxygenated fuels promote or suppress NH3 reactivity, and inform combustion strategies for high-efficiency, low-carbon engine systems.

  PublisherDOI

• Mechanistic Insights into the Suppression of Proton Intercalation and the Hydrogen Evolution Reaction through Phosphorus Doping in Tungsten Oxide

  ACS electrochemistry. · 2026-05-06

  articleOpen access

  The hydrogen evolution reaction (HER) is an inevitable parasitic process that limits the efficiency and selectivity of electrochemical hydrogenation reactions using water as the hydrogen source. Although introducing oxygen vacancies and heteroatom dopants into transition-metal oxides is widely employed to enhance hydrogenation activity, such modifications often inadvertently promote HER. Here, we demonstrate a counterintuitive suppression of proton intercalation and HER in metalloid phosphorus (P)-doped WO3 catalysts, with progressively stronger suppression at higher P-doping levels. Electrochemical impedance spectroscopy, Mott–Schottky analysis, and hydrogen bond dissociation free energy (H-BDFE) measurement reveal that, despite enhanced electronic conductivity, improved interfacial charge transfer, and decreased H-BDFE, phosphorus doping significantly increases the adsorption resistance associated with W–H* intermediate formation and reduces H* surface coverage, thereby suppressing HER kinetics. Density functional theory calculations further show that even though the W d-band center was downshifted toward its Fermi level, P-doping broadens the distribution of hydrogen binding strengths across oxygen sites of the WO3 catalysts, such that many sites bind hydrogen too weakly to support efficient proton intercalation. These insights reveal an alternative HER suppression mechanism whereby heteroatom doping enables local control of proton intercalation and hydrogen adsorption kinetics beyond conventional d-band tuning, proton/electron supply, or charge-transport limitations.

  PublisherDOI

• Femtosecond Laser Absorption Spectroscopy for Simultaneous Temperature and NH Concentration Measurements in An Ammonia/Hydrogen Flame

  2026-01-08

  articleSenior author

  A femtosecond ultraviolet laser absorption diagnostic for simultaneous temperature and NH concentration measurements is developed and demonstrated in an atmospheric ammonia/hydrogen flame produced by a Hencken burner. The diagnostic system provides high-accuracy, calibration-free, single-shot measurement of NH based on the (0, 0) band of the A3Π-X3Σ- electronic transition near 336 nm with an acquisition rate of 156 Hz. Theoretical NH absorbance is simulated using a line-by-line model. NH and temperature profiles along the flame central axis are measured. An estimated NH detection limit of 1.3 ppm was achieved. This diagnostic enables quantitative and time-resolved NH and temperature measurement, providing a new method for probing ammonia reaction kinetics in combustion and chemical synthesis.

  PublisherDOI

Recent grants

• Engineering Research Equipment: Laser Diagnostics for Microscale and Microwave Enhanced Combustion

  NSF · $89k · 2004–2006

• UNS: Highly Sensitive H02 Diagnostics and Oxidation Kinetics of Oxygenated Fuels at High Pressure

  NSF · $350k · 2015–2019

• Control of Volumetric Ignition and Thermal-Chemical Instability in Weakly Ionized Plasma for High Pressure Ultra-lean Combustion

  NSF · $360k · 2019–2023

Frequent coauthors

• Sang Hee Won

  77 shared

• Frederick L. Dryer

  University of South Carolina

  47 shared

• Aric C. Rousso

  Lawrence Livermore National Laboratory

  45 shared

• Hongtao Zhong

  The University of Texas at Austin

  45 shared

• Ziyu Wang

  Beijing Forestry University

  44 shared

• Timothy Y. Chen

  Princeton University

  43 shared

• Xingqian Mao

  Princeton University

  41 shared

• Christopher B. Reuter

  United States Naval Research Laboratory

  40 shared

Labs

• Combustion and Low Carbon Energy ConversionPI

Education

• Postdoctoral Fellow, Mechanical Engineering

  Tohoku University

  1995

• PhD, Mechanical Engineering

  Tohoku University

  1994

• MEng, Thermophysics

  Tsinghua University

  1988

• BEng, Thermophysics

  Tsinghua University

  1986

Awards & honors

• Distinguished Paper Awards from the International Symposium…
• NASA Director’s Certificate of Appreciation award (2011)
• Friedrich Wilhelm Bessel Research Award by the Alexander von…
• International Prize from Japanese Combustion Society (2018)
• Propellants & Combustion Award from the American Institute o…