Sustainable chemistry with plasmonic photocatalysts

Abstract

There is a pressing global need to increase the use of renewable energy sources and limit greenhouse gas emissions. Towards this goal, highly efficient and molecularly selective chemical processes that operate under mild conditions are critical. Plasmonic photocatalysis uses optically-resonant metallic nanoparticles and their resulting plasmonic, electronic, and phononic light-matter interactions to drive chemical reactions. The promise of simultaneous high-efficiency and product-selective reactions with plasmon photocatalysis provides a compelling opportunity to rethink how chemistry is achieved. Plasmonic nanoparticles serve as nanoscale 'antennas' that enable strong light-matter interactions, surpassing the light-harvesting capabilities one would expect purely from their size. Complex composite structures, combining engineered light harvesters with more chemically active components, are a focal point of current research endeavors. In this review, we provide an overview of recent advances in plasmonic catalysis. We start with a discussion of the relevant mechanisms in photochemical transformations and explain hot-carrier generation and distributions from several ubiquitous plasmonic antennae. Then we highlight three important types of catalytic processes for sustainable chemistry: ammonia synthesis, hydrogen production and CO₂ reduction. To help elucidate the reaction mechanism, both state-of-art electromagnetic calculations and quantum mechanistic calculations are discussed. This review provides insights to better understand the mechanism of plasmonic photocatalysis with a variety of metallic and composite nanostructures toward designing and controlling improved platforms for green chemistry in the future.

Keywords: hot carrier; photocatalysis; plasmonic; sustainable chemistry.

Figure 1:

Lifetime of plasmon due to electron-hole dephasing and associated hot carrier distributions. (A) The general process of plasmon decay: (i) excitation of the localized surface plasmon resonance (LSPR) results in an enhanced interaction cross-section with the incident light from the enhanced optical near-field. (ii) Non-radiative decay through Landau damping and pumping of non-equilibrium hot carriers. (iii) Hot-carrier thermalization through electron-electron scattering. The numbers of energetic carriers (also referred to as thermalized carriers) increases. (iv) Photothermal heating from electron-phonon interaction. (B) The energy distribution of the hot carriers (z axis) as the function of plasmon frequency (y axis) and hot carrier energy (x axis) in Al, Ag, Au, and Cu. The red part represents the hot carrier generation through phonon-assisted Landau damping (or intraband transition), and the blue part represents the direct photoexcitation of interband transition. Reproduced from ref. [22]. Copyright 2016 American Chemical Society.

Figure 2:

Plasmonic nitrogen fixation. (A) The wavelength-dependent reactivity (blue open dots and dashed curve) is well-correlated to the extinction spectrum (pink solid line) on a Au-Os nanoparticles for gas-phase ammonia synthesis (N₂ + 3H₂ → 2NH₃). Adapted from ref. [52] with permission. Copyright 2014 Elsevier B.V. (B) Ammonia synthesis in presence of water (N₂ + 6H⁺ + 6e⁻ → 2NH₃) on a AuRu core-antenna nanostructure under full-spectrum irradiation at 2 atm N₂. Adapted from ref. [53] with permission. Copyright 2019 American Chemical Society. (C) Stability test of ammonia synthesis on Au in presence of water on UiO-66 MOF. Adapted from ref. [63] with permission. Copyright 2019 American Chemical Society. (D) The plasmonic gas-phase ammonia synthesis with a commercial Ru-Cs/MgO catalyst driven by the thermal gradient. Adapted from ref. [59]. Copyright 2019 American Chemical Society. (E) Plasmonic photothermal gas-phase ammonia synthesis with a K/Ru/TiO_2−x H _x catalyst. Adapted from ref. [60] with permission. Copyright 2017 Elsevier B.V. (F) Stability of a porous plasmonic CuFe for nitrogen fixation with 1 atm N₂ in water. Adapted from ref. [62] with permission. Copyright 2020 American Chemical Society.

Figure 3:

Plasmonic gas-phase catalysis for H₂ generation. (A) Apparent activation energies under different wavelengths and power densities on a Cu-Ru surface alloy antenna reactor for NH₃ decomposition (2NH₃ → 2N₂ + 3H₂). Adapted from ref. [78] with permission. Copyright 2018 The American Association for the advancement of science. (B) 3D reactor to scale up the Cu-Ru and Cu-Fe catalysts in gram scale for ammonia decomposition with LED light. Adapted from ref. [79] with permission. Copyright 2022 The American Association for the advancement of science. (C) Stability test of CuRu for methane dry reforming (CH₄ + CO₂ → 2CO + 2H₂). Adapted from ref. [80] with permission. Copyright 2020 Springer Nature. (D) Production rate and selectivity evolution with varying temperature of Au-Pt/P25 for photothermal catalysis. Adapted from ref. [81] with permission. Copyright 2022 Elsevier Inc. (E) Reaction mechanism of Au on SiO₂ for direct photocatalytic and thermocatalytic H₂S decomposition. Adapted from ref. [31] with permission. Copyright 2022 American Chemical Society. (F) In-situ FTIR measurement to detect the intermediate species during photochemical transformation on CuZn alloy for methanol steam reforming (CH₃OH + H₂O → 3H₂ + CO₂). Adapted from ref. [10] with permission. Copyright 2021 American Chemical Society.

Figure 4:

Plasmonic gas-phase CO₂ hydrogenation. (A) Activation energies and selectivity of CO₂ hydrogenation towards methane on Rh/Al₂O₃ catalysts are tailored by light compared to the reaction in the dark. Adapted from ref. [9] with permission. Copyright 2017 Springer Nature. (B) CO₂ methanation reaction on Rh/TiO₂ catalysts utilizing both thermal and non-thermal effects with the temperature gradient in the catalyst bed. Adapted from ref. [98] with permission. Copyright 2018 American Chemical Society. (C) Al@MIL-53 for enlarged surface area for gas uptake and enhanced reverse water-gas shift reaction. Adapted from ref. [99] with permission. Copyright 2019 The American Association for the advancement of science. (D) Schematic of hot-electron induced chemistry at Al-Cu₂O interface for reverse water-gas shift reaction. Adapted from ref. [5] with permission. Copyright 2017 Springer Nature. (E) In-operando FTIR measurement of reaction steps under different temperatures for photothermal CO₂ methanation on a Rh/al catalyst. Adapted from ref. [8] with permission. Copyright 2021 American Chemical Society.