Molecular-captured hot-electron detection in single-atom alloy antennas.

Hot electrons are ubiquitous in diverse physical and chemical processes, since they are involved in the energy transfer of elementary processes such as adsorption, diffusion and desorption of reactants. However, hot electrons have short lifetimes (∼few fs) and small mean free paths (∼<10 nm), which are inherently difficult to detect via conventional in situ pumping techniques. Here, we designed a spectrally tunable photoexcitation desorption analyser, a tool for tracking hot-electron generation, which enables mechanistic studies of hot-electron generation and transfer in single-atom alloy antennas in real time under flow conditions by a variety of molecular probes (CO, CO₂ and various hydrocarbons). Long-lived hot electrons arise because electrons with discrete energy levels spaced by several hundred meV in individual atoms cannot relax to form phonons. Furthermore, we utilize the hot electrons generated by single-atom alloy antenna-modified photocatalysts under illumination to produce green syngas from carbon dioxide and water, achieving an efficiency one order of magnitude higher than traditional powder photocatalysis. Our discovery provides an unprecedented perspective for the detection of hot-electron generation and has implications for future advancements in nanophotonics.