Fabricating Appropriate Band-Edge-Staggered Heterosemiconductors with Optically Activated Au Nanoparticles via Click Chemistry for Photoelectrochemical Water Splitting

Semiconductor-mediated photoelectrochemical (PEC) water splitting to generate hydrogen and oxygen has gained tremendous attention as it has the capability to overcome the world energy crisis. However, limited solar light absorption and a high charge carrier recombination rate are major bottlenecks in achieving the desired efficiency of PEC devices. Fabrication of semiconductor-metal/metal oxide heterostructure holds a great promise to overcome these bottlenecks as it facilitates solar light absorption, separation, and transport of charge carriers. To this end, we demonstrate a fabrication methodology to design stable tailored heterostructures via click chemistry. To test the proposed methodology, we choose gold (Au), rutile-TiO2 (R-TiO2), and anatase TiO2 (A-TiO2) as model system and designed tailored triad heterostructure, i.e., Au@R-TiO2@A-TiO2, over stainless steel, and demonstrated its application in photoelectrochemical (PEC) water splitting. We hypothesize that the presence of Au and R-TiO2/A-TiO2 interface in triad heterostructures plays an important role in improving the solar light absorption and charge carrier separation, respectively. This is supported by the PEC water splitting measurements which shows that the fabricated Au@R-TiO2@A-TiO2@SS triad heterostructure possesses highest applied bias photoconversion efficiency (ABPE) of similar to 0.4% at 0.95 V applied bias and electrical and solar power-to-hydrogen (ESPH) efficiency of similar to 4.0% at 1.1 V applied bias as compared to other fabricated heterostructures over stainless steel (R-TiO2@A-TiO2@SS, R-TiO2@SS, A-TiO2@SS, and Au@SS). Further, we have also studied the interfacial kinetics at electrode/electrolyte interface of fabricated heterostructures via electrochemical impedance spectra (EIS) which demonstrate the improved charge carrier transport in Au@R-TiO2@A-TiO2@SS triad heterostructure.