Hot electron reduction of iron ferricyanide was observed at room temperature using thin Pt films on n-Si (111) and n-Si (100) substrates. The average Schottky barrier heights on both (111) and (100), as measured by open-circuit space-charge capacitance measurements, were 0.84 +/- 0.01 to 0.81 +/- 0.01 eV, for Pt film thickness from 100 to 700 angstrom. Below 100 angstrom the barrier height increased slightly with thickness. All Tafel slopes were 60 mV/decade. At HF etched n-Si (111) surfaces, the exchange current for electron transfer was determined as a function of Pt film thickness using 0.3M each potassium Fe(CN)6(-3/-4), pH 6.0. The exchange current declined from 3.3 x 10(-6) A cm-2 at 25 angstrom to 8 x 10(-7) A cm-2 at t greater-than-or-equal-to 100 angstrom Pt. For Si (111), the energy parameter, delta, varied from 0.55 +/- 0.025 at zero thickness to 0.83 +/- 0.025 eV at t greater-than-or-equal-to 80 angstrom and remained constant to 700 angstrom signifying fully cooled electrons for such thicker films. For Si (100), delta varied from 0.55 +/- 0.025 at zero thickness to 0.89 eV +/- 0.025 at t greater-than-or-equal-to 40 angstrom and remained constant. For both (111) and (110), the large magnitude of delta for the thinnest films indicates the major cooling occurs at the Pt/n-Si interface rather than within the Pt film.