Scientific insight into the dual role of Cu-cocatalysts for electron injection onto schottky junctions: sunlight driven H 2 production with Cu@Si-CdS system †

Abstract

Current work reveal the successful synthesis of Cu@Si-CdS catalysts and their application in sunlight-driven hydrogen generation. Hydrothermal approach was employed to achieve the required characteristics and compositional characteristics, while the synthesis reactions were carefully controlled to ensure precise sillicon doping and uniform copper loading. To assess optical and structural characteristic of catalysts analytical techniques such as, XRD, SEM, AFM, UV-Vis/DRS, FT-IR, PL, Raman and VSM have been employed and justified. Photoelectrochemical experiments (i.e., photocurrent and elctron impedence measurements were conducted to confirm the charge separation andtransfer onto the active sites. EDX and XPS techniques were used to confirm the purity and chemical compositions. Photoreactions were carried out in 140 mL glass reactor (Velp-Sci), whereas hydrogen evolution was monitored via gas charamatography equiped with thermal conductivity detector (GC-TCD). Catalytic activities i.e. hydrogen evolution performances indicated that Cu@Si-CdS catalysts deliver 23.85 mmol g -1 h -1 of hydrogen. This activity is six times higher than that of pristine CdS or catalysts lacking Si dopants and Cu cocatalysts. Superior activities of Cu@Si-CdS catalysts is ascribed to presence of silicon dopants and localized surface plosmon resonance (LSPR) of Cu-cocatalysts. During photoreactions, Si dopants generates additional energy levels, resulting extended light absorption capability of catalysts. Additionally, metal cocatalysts (i.e. Cu in present work) develop schottky junctions that facilitates the rectification of charges onto the active sites and restrict recombinations. To determine the optimal conditions, various factors including temperature, pH, light intensity and catalyst dose were precisely assessed and optimized. These results demonstrates that Cu@Si-CdS catalysts system hold significant potentially for sustainable hydrogen production. potential to serve as an alternative fuel to replace conventional fossil fuels. However, molecular hydrogen does not occur freely in nature and must be generated from renewable feedstocks such as water and biomass 6 . Hydrogen production can be achieved thorugh several