Synchronization of charge carrier separation by tailoring the interface of Si-Au-TiO2 heterostructures via click chemistry for PEC water splitting

- Versatile technique to devise Si-Au-TiO2 heterostructure for PEC water splitting.
- Capitalizing energized photo electrons of Si and preventing surface oxide formation.
- Synchronized charge carrier transport to overcome electron-hole recombination.
- Achieved photo-conversion efficiency (ABPE) of ~0.4% at 0.9 V applied bias.

Electrochemical potential gradients that are established due to appropriate band edge alignment in heterostructures can synchronize the movement of electron and hole in opposite direction. Such synchronization is critical for efficient photoelectrochemical devices and can be achieved by tailoring the interface of heterostructures. To this end, we fabricate a tailored interface of Si-Au-TiO2 heterostructure over stainless steel ((Si-Au-TiO2)/SS) for effective charge carrier separation. The fabricated electrode possesses the following tailored interfaces to enhance the charge-carrier separation/transport: 1) gold nanoparticles form interface (sandwiched) with Si as well as TiO2; 2) Si, Au, and TiO2 form the interface with SS, 3) Si-TiO2, and Si-Au interface facilitates the quenching of h+ generated in Si (via electron transfer from TiO2 and Au to Si) which facilitates electron transport to counter electrode for hydrogen generation, and 4) TiO2 forms the interface with the electrolyte solution to facilitate hole transport. Photoelectrochemical (PEC) measurements of (Si-Au-TiO2)/SS heterostructure exhibits higher performance compared to other heterostructures ((Au-Si)/SS, (Au-TiO2)/SS, (Si-TiO2)/SS, TiO2/Au/Si/SS, and Si/Au/TiO2/SS), substantiating the importance of synchronized charge transport in PEC systems. Further, electrochemical impedance spectroscopy (EIS) studies also support the synchronized charge transport in the tailored heterostructure ((Si-Au-TiO2)/SS) compared to control samples. The calculated applied bias to photo-conversion efficiency (ABPE) of ~0.4%@~0.9 V applied bias, intrinsic solar to chemical conversion efficiency (ISTC) of ~0.085 (or 8.5%) @1.66 V vs. RHE and electrical and solar power-to-hydrogen (ESPH) conversion efficiency of ~3.3%@~1.0 V applied bias.