Immobilization method dictates the photoelectrochemical glycerol oxidation performance of semiconductor catalyst assemblies.

Photoelectrochemistry provides a direct route to convert sunlight into valuable chemicals. However, high-performance photoelectrode architectures often require complicated synthesis steps and expensive instrumentation. Although physical immobilization (e.g., spray coating) of catalyst particles on semiconductors seems to be a simple and universal approach, it is rarely implemented to prepare photoelectrodes. Here, we highlight challenges associated with such deposition strategies and demonstrate the importance of rational photoelectrode design. Specifically, we introduce metal interlayers (Pd, Au, or Ni) between n-type Si and a spray-coated PdAu catalyst. We show that these interlayers are essential for generating photopotential at the interface, while the PdAu catalyst governs C3 selectivity during glycerol oxidation. We also demonstrate that the interlayer determines key performance metrics (e.g., photopotential, photocurrent density, and stability). With this approach, the best-performing PdAu/Au/Si and PdAu/Ni/Si photoelectrodes can deliver high reaction rates (>100 mA cm-2) with sufficient stability even at higher illumination intensities (50 suns).