Unlocking the full potentials of renewable energy calls for advanced technologies of energy conversion and storage. Photo-electrochemistry by semiconductor electrode can achieve one-step conversion of solar energy into chemical fuels, while its practical application is limited by long-term durability. Switching from graphite to Li-metal anode can double the energy density of state-of-art Li battery but cause rapid capacity fading upon cycling. Unifying my extensive expertise in Surface and Interface Sciences enables a fundamental look at the nature of Interphase-confined Electrochemistry (ICE) that is urgently necessary to break through the persisting challenges of emerging energy technologies.

My PhD thesis at Caltech has delivered three key mechanisms for understanding the stability of semiconductor photoelectrodes for solar fuels. First, accelerating catalytic kinetics of fuel-forming reactions can suppress corrosion pathways at semiconductor surface that are competitive but less favored by thermodynamics. Also, their photo-electrochemical behaviors are sensitive to altered surface stoichiometry producing unfavorable surface states. Architectural integrity is equally significant for multi-layered solar-fuel devices where corrosion of specific functional layer can cause individual failure mode. 

Stabilization by Catalytic Kinetics 

Investigations of the stability of etched or platinized p-InP(100) photocathodes for solar-driven hydrogen evolution in acidic or alkaline aqueous electrolytes, Energy Environ. Sci., 2021, 14, 6007-6020

Surface Stoichiometry Matters 

Investigations of the stability of GaAs for photoelectrochemical H2 evolution in acidic or alkaline aqueous electrolytes, J. Mater. Chem. A, 2021,9, 22958-22972

Architectural Integrity for Solar Fuels

Failure Modes of Platinized pn+-GaInP Photocathodes for Solar-Driven H2 Evolution, ACS Appl. Mater. Interfaces 2022, 14, 23, 26622–26630

To follow, my postdoc works at Stanford is bridging a knowledge gap from interfacial electrolyte reactivity to the formation of solid-electrolyte interphase (SEI) at Li metal anode (LMA). By innovating X-ray photoelectron spectroscopy (XPS), I managed to reveal underlying electron-transfer pathways causing electrolyte breakdown, and its kinetic dependence on thermodynamic driving force. These fundamentals of SEI chemistry further illustrate the dynamic assembly of passivating layer against dissolution.

XPS for Battery Chemistry

Degradation and Speciation of Li Salts during XPS Analysis for Battery Research, ACS Energy Lett. 2022, 7, 3270–3275

During my PhD at Caltech, I also extensively collaborated with Prof. Harry B. Gray and Dr. Nathan Dalleska on analytical verification of N2-reduction electrocatalysis. We established a new protocol of isotopic quantification of ammonia with low detection-limit and high sensitivity. 

Analytical Nitrogen Catalysis

Isotopically Selective Quantification by UPLC-MS of Aqueous Ammonia at Submicromolar Concentrations Using Dansyl Chloride Derivatization, ACS Energy Lett., 2020, 5, 5, 1532–1536

Funding Sources and Beyond

Sun, Lewis, Xiang et al, AEM, 2016, 6(13), 1600379.