Fig. 1: Detection of hot electrons generated on Pt nanowires/TiO₂ nanodiode.

a Schematic of hot electron generation on the Pt nanowires/TiO₂ catalytic nanodiode during exothermic methanol oxidation. Methanol oxidation occurs, and CO₂ and methyl formate are produced at the Pt-TiO₂ interface formed by the bonding of Pt nanowires and TiO₂. In this process, non-adiabatic energy dissipation occurs and hot electrons are generated on the nanodiode surface. SEM image of Pt nanowire arrays with a width of 20 nm and a pitch of 50 nm. b Energy band diagram for Schottky nanodiode of the Pt nanowires supported on TiO₂. Hot electrons excited from the surface chemical reaction can be detected as a steady-state chemicurrent by charge transfer if their excess chemical energy is large enough to overcome the Schottky barrier of the Pt-TiO₂ junction. c TEM image of the transferred Pt nanowire arrays on TEM grid with a width of 20 nm. d Current–voltage (I–V) curves for the Pt nanowires/TiO₂ catalytic nanodiode. The solid line is a fit of the obtained I–V curve to the thermionic emission theory. The obtained Schottky barrier height was 0.85 eV. e Current density associated with the methanol oxidation measured on the Pt nanowires/TiO₂ with increased reaction temperature. The differences in the magnitude of the currents measured with and without catalytic reaction were associated with reaction-induced hot electrons generated on the catalytic nanodiode (i.e., net chemicurrent).