Thermoelectrics‐Mediated Photon‐Phonon‐Electron Coupling Enables Unconventional Thermal Contributions in Plasmonic Catalysis

Plasmonic catalysis represents a promising platform to synergize photo‐, thermal‐ and electric effects in chemical conversion, converging diverse driving forces into chemical energy. Unfortunately, the rapid and substantial heat loss owing to the significant spatial and temporal mismatch between transient phonon scattering processes and slower reaction dynamics remains a crucial challenge, particularly for aqueous‐phase reactions and exergonic processes. Herein, through the tandem union of surface plasmon and thermoelectric responses, we achieve distinct light‐driven photon‐phonon‐electron coupling that leads to unconventional photothermal contributions in a MXene‐Au plasmonic nanocatalyst. Upon resonant photoexcitation, the catalyst induces substantial photothermal conversion and creates an intrinsic lateral temperature gradient, extracting both thermoelectric and plasmonic electrons toward efficient nitrate reduction catalysis. The light‐driven interconvertable phonon‐electron coupling enables polarization activation of nitrate reactant as well as modulation of its reaction pathway, leading to unprecedented thermal contribution as well as photo‐enhancement in ammonia production, and opening new avenues for generalized designs of next‐generation energy conversion systems that effectively synergize photo‐, thermal and electric energies.