Figure 4.
Schematic band diagram for a GaAs/GaInP heterojunction exposed to a CH3OH + O2 solution. The diagram also shows indicative band alignments for methanol oxidation and oxygen reduction potentials at standard conditions and illustrates various competing mechanisms through which the temperature can affect the performance, including the accelerated rates of redox reactions (Temp. 1), escape of dissolved O2 molecules from the semiconductor surface (Temp. 2), nonradiative recombination of the injected charge carriers (Temp. 3), and the poisoning effect as a result of CO absorption on the surface (Temp. 4).