Plasmon Resonant Enhancement of Photo(electro)catalysis (i.e., Solar Energy Storage) and Plasma-enhanced Combustion of Carbon-free (i.e., “Green”) Fuels

We present plasmon resonant enhancement of photocatalytic solar energy conversion. Here, the hydrogen evolution reaction (i.e., solar water splitting) is driven by short-lived hot electrons photogenerated in plasmon-resonant grating structures. By illuminating corrugated metal surfaces (520 nm grating period) with a 785 nm laser at varying incident angles, sharp peaks in electrochemical photocurrent and dips in photoreflectance appear at angles matching the plasmon resonance conditions. The electrochemical potential of the photoelectrode is then scanned over the range from -0.8V to +1.2V vs. NHE, enabling us to perform spectroscopy of the charge transfer resonance that occurs when the energy of the hot electrons matches the redox potential of the dominant half reaction in solution. Notably, Pt-coated gratings demonstrate a 64-fold plasmon-resonant enhancement, while bare gratings show 28-fold enhancement.



Additionally, nanosecond pulse transient plasma enables stable, single-fuel ammonia combustion in a modified natural gas engine over a wide range of equivalence ratios (ϕ = 0.78 to 1.23), outperforming conventional dual-fuel systems. We also demonstrate enhanced combustion of H2 through the transient plasma-based approach, which enables the engine to run without producing a significant amount of NOx. Key mechanisms include advanced ignition timing and multi-pulse high voltage discharge, generating ionic winds, turbulence, and larger flame kernel surface area. The process facilitates stable pure ammonia combustion with no need for additional engine modifications, offering a promising alternative to traditional ignition systems.



[1] “Photo-excited Hot electron Catalysis in Plasmon Resonant Grating Structures with Platinum, Nickel, and Ruthenium Coatings” Indu Aravind, Yu Yun Wang, Yu Wang, Ruoxi Li, Zhi Cai, Bofan Zhao, Boxin Zhang, Sizhe Weng, Rifat Shahriar, and Stephen Cronin. ACS Applied Materials & Interfaces, 16, 17393–17400 (2025).



[2] “Stable combustion of ammonia in an internal combustion engine: A single fuel approach enabled by multi-pulse transient plasma ignition” Boxin Zhang, Mariano Rubio, Fokion Egolfopoulos, Stephen B. Cronin; Fuel, Volume 381, Part C, 1 February 2025, 133502 (2025).