Role of electronically coupled in situ grown silver sulfides (Ag2S) nanoparticles with TiO2 for the efficient photoelectrochemical H2 evolution

A solution-processed in situ grown synthesis method has been developed to grow electronically coupled silver sulfide (Ag2S) nanoparticles (NPs) inside a titanium oxide (TiO2) thin film. Taking the advantage of better charge transport between Ag2S and TiO2, this composite thin film has been utilized for electro-photocatalytic H-2 generation. This thin film growth requires three successive steps, including sol-gel derived ion-conducting thin film fabrication containing loosely bound light ion (Li+) followed by ion-exchange (with Li+ <-> Ag+) and subsequent sulfurization process. This entire solution-processed deposition technique is capable to fabricate cost-effective large area Ag2S-TiO2 thin film containing Ag2S NPs ranging similar to 10-70 nm. Since, Ag2S has a lower band gap and consider as a promising material for photo-electrochemical H-2 generation, therefore Ag2S (NPs)-TiO2 thin film is grown on three different substrates, including fluorine-doped tin oxide (FTO), FTO/TiO2 (sol-gel), and FTO/TiO2 (NPs) to fabricate photoanode for this study. A comparative photo-electrocatalytic measurement of these three different Ag2S(NPs)-TiO2 thin film coated photoanodes showed that sample on FTO/TiO2 (NPs) substrate generate highest photocurrent of density similar to 50 mA cm(-2) at 0.5 V vs NHE in 1 M KOH solution which is three orders higher than pure TiO2 and stable for more than 1.5 h, indicating it's excellent potential application for photoelectrochemical water splitting. The photocurrent generation of this Ag2S-TiO2 thin film is significantly higher than earlier reported Ag2S-TiO2 system, which is originated due to the reduced carrier recombination from electronically coupled Ag2S/TiO2 interface state of such in situ grown Ag2S NPs. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.