@article {48980, title = {Facile one-pot synthesis of Cu x O/TiO2 photocatalysts by regulating Cu oxidation state for efficient solar H2 production}, journal = {ACS Applied Energy Materials }, volume = {7}, year = {2023}, month = {DEC }, pages = {104-116}, type = {Article}, abstract = {

Development of highly efficient CuxO/TiO2 photocatalysts by regulating the oxidation state of Cu exclusively in either single or mixed oxidation state(s) is desirable but difficult to achieve without employing any external reagents. The present work describes a one-pot synthesis strategy to obtain CuxO/TiO2 photocatalysts with Cu in +1 and/or +2 by using a suitable combination of ethylene diamine tetra acetic acid (EDTA) and ethylene diamine, carefully varying the Cu content, and heat treatment process. CuxO/TiO2 nanocomposite catalysts were characterized thoroughly by physicochemical methods. Textural analysis indicates a high dispersion of CuxO on porous TiO2 with p-n heterojunctions between them in CuxO/TiO2 catalysts. UV-visible spectral analysis suggests the presence of CuxO on TiO2 with significantly extended absorption from the UV to the visible region. X-ray photoelectron spectroscopy (XPS) analysis indicates a strong synergetic interaction between TiO2 and CuxO due to the comparable CB potential and p-n heterojunction at the interface among them. Photoelectrochemical studies demonstrate excellent charge-carrier separation efficiency, low charge-transfer resistance, and high double-layer capacitance with Cu2O/TiO2 photocatalysts. Photocatalytic efficacy of a CuxO/TiO2 nanocomposite in thin-film form has been demonstrated for solar hydrogen generation in sunlight. The incorporation of Cu+ in TiO2 largely improves the H-2 production, and all of the CuxO/TiO2 nanocomposites in thin-film form exhibited higher efficiency compared to their particulate/suspension counterpart. Among the composite catalysts, TiCu-1 in thin-film form, with Cu exclusively in +1 oxidation state, exhibited a high hydrogen production rate of 7.06 mmol/hg, which is 6 times higher than its suspension counterpart; also catalysts containing mixed Cu-oxidation states exhibited about 60-70\% activity as that of TiCu-1. The superior performance of Cu2O/TiO2 nanocomposites in thin-film form was due to their enhanced light harvesting ability, high mass transfer rate, and easy accessibility of the reactant species to the active sites.

}, keywords = {heterojunction, Photocatalysis, Solar hydrogen, thin film, titania}, issn = {2574-0962}, doi = {10.1021/acsaem.3c02272}, author = {Rajendran, Sivaraj and Mani, Sunesh S. and Nivedhitha, Thazhath R. and Asoka, Anantha Krishnan and Arun, Pushkaran S. and Mathew, Thomas and Gopinath, Chinnakonda S.} } @article {49621, title = {Multifunctional NiO/Ti3+-TiO2 for concurrent water reduction and glycerol oxidation to value added products by sunlight driven photocatalysis}, journal = {Journal of Materials Chemistry A}, volume = {13}, year = {2025}, month = {JAN}, pages = {2105-2120}, type = {Article}, abstract = {

The present work describes the synthesis of bifunctional-mesoporous-self-doped Ti3+ containing NiO/TiO2 photocatalysts for concurrent utilization of e- and h+ to produce H2 and value-added products (VAPs), respectively, from aqueous glycerol. UV-vis diffuse reflectance results and band gap analysis revealed an improved light absorption due to integration of Ni2+ with Ti3+/TiO2. Various electrochemical, PL and TRPL spectral analyses demonstrate p-n heterojunction formation between NiO and Ti3+-TiO2, which enhances charge separation and helps in achieving improved activity. HRTEM analysis of NiO/Ti3+-TiO2 nanocomposites revealed that NiO is highly dispersed on TiO2 with interfacial heterojunctions between them. XPS results demonstrate the partial reduction of Ti4+ to Ti3+ and Ni-Ti synergetic interaction in NiO/TiO2 to form NiO/Ti3+-TiO2 nanocomposites. EXAFS studies show that the Ni-O bond distance is similar to that of NiTiO3 suggesting electronic integration of components of the photocatalyst by forming a Ni2+-O-Ti3+/Ti4+ lattice network. Ni2+/Ti3+-TiO2 nanocomposites as a bifunctional photocatalyst exhibited significantly enhanced activity in H2 production and conversion of glycerol to VAPs, namely, glycolaldehyde, 1,3-dihydroxyacetone, and formic acid; formation of these products highlights not only oxidation, but also C-C cleavage of glycerol. The NiO/Ti3+-TiO2 photocatalysts fabricated in thin film form displayed higher photocatalytic efficiency than their powder counterpart. Among NiO/Ti3+-TiO2 nanocomposites NiT-3 exhibits the highest H2 yield at 15.62 mmol h-1 g-1, which is 38 times higher than that of bare TiO2. The enhanced photocatalytic activity is ascribed to the high charge carrier density, the synergistic interaction between Ni2+ and Ti3+-TiO2, formation of a p-n heterojunction at the interface between NiO and Ti3+-TiO2 and effective utilization of charge carriers for redox reactions.

}, issn = {2050-7488}, doi = {10.1039/d4ta06910b}, author = {Rajendran, Sivaraj and Saju, Simi and Mani, Sunesh S. and Asoka, Anantha Krishnan and Saha, Arindam and Arun, Pushkaran S. and Ghosh, Biplab and Mathew, Thomas and Gopinath, Chinnakonda S.} } @article {49446, title = {Multifunctional NiO/Ti3+{\textendash}TiO2 for concurrent water reduction and glycerol oxidation to value added products by sunlight driven photocatalysis}, journal = {Journal of Materials Chemistry A}, volume = {13}, year = {2025}, month = {JAN}, pages = {2105-2120}, type = {Article}, abstract = {

The present work describes the synthesis of bifunctional-mesoporous-self-doped Ti3+\ containing NiO/TiO2\ photocatalysts for concurrent utilization of e-\ and h+\ to produce H2\ and value-added products (VAPs), respectively, from aqueous glycerol. UV-vis diffuse reflectance results and band gap analysis revealed an improved light absorption due to integration of Ni2+\ with Ti3+/TiO2. Various electrochemical, PL and TRPL spectral analyses demonstrate p{\textendash}n heterojunction formation between NiO and Ti3+{\textendash}TiO2, which enhances charge separation and helps in achieving improved activity. HRTEM analysis of NiO/Ti3+{\textendash}TiO2\ nanocomposites revealed that NiO is highly dispersed on TiO2\ with interfacial heterojunctions between them. XPS results demonstrate the partial reduction of Ti4+\ to Ti3+\ and Ni{\textendash}Ti synergetic interaction in NiO/TiO2\ to form NiO/Ti3+{\textendash}TiO2\ nanocomposites. EXAFS studies show that the Ni{\textendash}O bond distance is similar to that of NiTiO3\ suggesting electronic integration of components of the photocatalyst by forming a Ni2+{\textendash}O{\textendash}Ti3+/Ti4+\ lattice network. Ni2+/Ti3+{\textendash}TiO2\ nanocomposites as a bifunctional photocatalyst exhibited significantly enhanced activity in H2\ production and conversion of glycerol to VAPs, namely, glycolaldehyde, 1,3-dihydroxyacetone, and formic acid; formation of these products highlights not only oxidation, but also C{\textendash}C cleavage of glycerol. The NiO/Ti3+{\textendash}TiO2\ photocatalysts fabricated in thin film form displayed higher photocatalytic efficiency than their powder counterpart. Among NiO/Ti3+{\textendash}TiO2\ nanocomposites NiT-3 exhibits the highest H2\ yield at 15.62 mmol h-1\ g-1, which is 38 times higher than that of bare TiO2. The enhanced photocatalytic activity is ascribed to the high charge carrier density, the synergistic interaction between Ni2+\ and Ti3+{\textendash}TiO2, formation of a p{\textendash}n heterojunction at the interface between NiO and Ti3+{\textendash}TiO2\ and effective utilization of charge carriers for redox reactions.

}, doi = {https://doi.org/10.1039/D4TA06910B}, author = {Rajendran, Sivaraj and Saju, Simi and Mani, Sunesh S. and Asoka, Anantha Krishnan and Saha, Arindam and Arun, Pushkaran S. and Ghosh, Biplab and Mathew, Thomas and Gopinath, Chinnakonda S.} }