@article {46446, title = {Electrocatalysis of oxygen reduction reaction on shape-controlled pt and pd nanoparticles-importance of surface cleanliness and reconstruction}, journal = {Frontiers in Chemistry}, volume = {7}, year = {2019}, month = {OCT}, pages = {648}, type = {Review}, abstract = {

Shape-controlled precious metal nanoparticles have attracted significant research interest in the recent past due to their fundamental and scientific importance. Because of their crystallographic-orientation-dependent properties, these metal nanoparticles have tremendous implications in electrocatalysis. This review aims to discuss the strategies for synthesis of shape-controlled platinum (Pt) and palladium (Pd) nanoparticles and procedures for the surfactant removal, without compromising their surface structural integrity. In particular, the electrocatalysis of oxygen reduction reaction (ORR) on shape-controlled nanoparticles (Pt and Pd) is discussed and the results are analyzed in the context of that reported with single crystal electrodes. Accepted theories on the stability of precious metal nanoparticle surfaces under electrochemical conditions are revisited. Dissolution, reconstruction, and comprehensive views on the factors that contribute to the loss of electrochemically active surface area (ESA) of nanoparticles leading to an inevitable decrease in ORR activity are presented. The contribution of adsorbed electrolyte anions, in-situ generated adsorbates and contaminants toward the ESA reduction are also discussed. Methods for the revival of activity of surfaces contaminated with adsorbed impurities without perturbing the surface structure and its implications to electrocatalysis are reviewed.

}, keywords = {Adsorption, Dissolution, oxygen reduction reaction, Palladium, platinum, reconstruction, shape-control, surface cleaning}, issn = {2296-2646}, doi = {10.3389/fchem.2019.00648}, author = {Devivaraprasad, Ruttala and Nalajala, Naresh and Bera, Bapi and Neergat, Manoj} } @article {46350, title = {Electronic integration and thin film aspects of Au-Pd/rGO/TiO2 for improved solar hydrogen generation}, journal = {ACS Applied Materials \& Interfaces}, volume = {11}, year = {2019}, month = {SEP}, pages = {32869-32878}, type = {Article}, abstract = {

In the present work, we have synthesized noble bimetallic nanoparticles (Au-Pd NPs) on a carbon-based support and integrated with titania to obtain Au-Pd/C/TiO2 and Au-Pd/rGO/TiO2 nanocomposites using an ecofriendly hydrothermal method. Here, a 1:1 (w/w) Au-Pd bimetallic composition was dispersed on (a) high-surface-area (3000 m(2) g(-1)) activated carbon (Au-Pd/C), prepared from a locally available plant source (in Assam, India), and (b) reduced graphene oxide (rGO) (Au-Pd/rGO); subsequently, they were integrated with TiO2. The shift observed in Raman spectroscopy demonstrates the electronic integration of the bimetal with titania. The photocatalytic activity of the above materials for the hydrogen evolution reaction was studied under 1 sun conditions using methanol as a sacrificial agent in a powder form. The photocatalysts were also employed to prepare a thin film by the drop-casting method. Au-Pd/rGO/TiO2 exhibits 43 times higher hydrogen (H-2) yield in the thin film form (21.50 mmol h(-1) g(-1)) compared to the powder form (0.50 mmol h(-1) g(-1)). On the other hand, Au-Pd/C/TiO2 shows 13 times higher hydrogen (H-2) yield in the thin film form (6.42 mmol h(-1) g(-1)) compared to the powder form (0.48 mmol h(-1) g(-1)). While powder forms of both catalysts show comparable activity, the Au-Pd/rGO/TiO2 thin film shows 3.4 times higher activity than that of Au-Pd/C/TiO2. This can be ascribed to (a) an effective separation of photogenerated electron-hole pairs at the interface of Au-Pd/rGO/TiO2 and (b) the better field effect due to plasmon resonance of the bimetal in the thin film form. The catalytic influence of the carbon-based support is highly pronounced due to synergistic binding interaction of bimetallic nanoparticles. Further, a large amount of hydrogen evolution in the film form with both catalysts (Au-Pd/C/TiO2 and Au-Pd/rGO/TiO2) reiterates that charge utilization should be better compared to that in powder catalysts.

}, keywords = {bimetal, Photocatalysis, surface plasmon resonance, TiO2, water splitting}, issn = {1944-8244}, doi = {10.1021/acsami.9b07070}, author = {Tudu, Bijoy and Nalajala, Naresh and Reddy, Kasala P. and Saikia, Pranjal and Gopinath, Chinnakonda S.} } @inbook {47467, title = {Functionalization of graphene - a critical overview of its improved physical, chemical and electrochemical properties}, booktitle = {Surface Engineering of Graphene}, year = {2019}, pages = {139-173}, publisher = {Springer}, organization = {Springer}, abstract = {Graphene, the 2D allotrope of carbon, is reported to be functionalized with a plethora of organic and inorganic species. This functionalization imparts significant improvement in the physical, chemical and electrochemical properties of graphene. The covalent and non-covalent functionalization of graphene with electron-rich organic moieties and heteroatoms is focused on different sections of this chapter. The focus is laid on the improvement in physical, chemical and electrochemical properties of graphene achieved through this functionalization. The enhancement in electrocatalytic activity of non-metal-doped graphene towards the oxygen reduction reaction, methanol oxidation reaction and photocatalysis is covered. Towards the end, the potential uses of functionalized graphene for selected applications like biosensors, fuel cells and dye-sensitized solar cells are also discussed.}, doi = {10.1007/978-3-030-30207-8_6}, author = {Singh, Ramesh Kumar and Nalajala, Naresh and Kar, Tathagata and Schechter, Alex} } @article {46189, title = {Why the thin film form of a photocatalyst is better than the particulate form for direct solar-to-hydrogen conversion: a poor man{\textquoteright}s approach}, journal = {RSC Advances}, volume = {9}, year = {2019}, month = {FEB}, pages = {6094-6100}, type = {Article}, abstract = {

We demonstrated an easy method to improve the efficiency of photocatalysts by an order of magnitude by maximizing light absorption and charge carrier diffusion. Degussa titania (P25) and Pd/P25 composite photocatalyst thin films coated over regular glass plates were prepared and evaluated for solar hydrogen production in direct sunlight with aqueous methanol. It is worth noting that only UV light present in direct sunlight (similar to 4\%) was absorbed by the catalysts. The hydrogen production activities of catalysts were compared for thin film and particulate forms at 1 and 25 mg levels. The hydrogen yield values suggested that 1 mg thin film form of Pd/P25 provided 11-12 times higher activity than 25 mg powder form. Comparable light absorption throughout the entire thickness of photocatalyst device and better contact of nanostructures that enabled the charge diffusion and charge utilization at redox sites are the reasons for high efficiency. While solar cells require charge carriers to diffuse through long distances of microns, they are utilized locally in an ensemble of particles (of nanometres) for hydrogen generation in photocatalyst thin films; this concept was used effectively in the present work.

}, issn = {2046-2069}, doi = {10.1039/c8ra09982k}, author = {Nalajala, Naresh and Patra, Kshirodra Kumar and Bharad, Pradnya A. and Gopinath, Chinnakonda S.} } @article {46792, title = {Can half-a-monolayer of pt simulate activity like that of bulk pt? solar hydrogen activity demonstration with quasi-artificial leaf device}, journal = {ACS Applied Materials \& Interfaces}, volume = {12}, year = {2020}, month = {JUL }, pages = {30420-30430}, type = {Article}, abstract = {

Pt is the best cocatalyst for hydrogen production. It is also well-known that the surface atomic layer is critical for catalysis. To minimize the Pt content as cocatalyst, herein we report on half-a-monolayer of Pt (0.5 theta(Pt)) decorated on earth-abundant Ni-Cu cocatalyst, which is integrated with a quasiartificial leaf (QuAL) device (TiO2/ZnS/CdS) and demonstrated for efficient solar hydrogen production. For the QuAL, TiO2 is sensitized with ZnS and CdS quantum dots by the SILAR method. The 0.5 theta(Pt)-decorated Ni-Cu shows an onset potential of 0.05 V vs reversible hydrogen electrode for the hydrogen evolution reaction, which is almost similar to that of commercial Pt/C. Photoactivity of the present QuAL device with either bulk Pt or 0.5 theta(Pt)-coated Ni-Cu cocatalyst is, surprisingly, equal. Our findings underscore that a fraction of a monolayer of Pt can enhance the activity of the cocatalyst, and it is worth exploring further for the high activity associated with atomic Pt and other noble metals.

}, keywords = {artificial leaf, nickel-copper, Photocatalysis, platinum, Solar hydrogen}, issn = {1944-8244}, doi = {10.1021/acsami.0c07431}, author = {Bajpai, Himanshu and Patra, Kshirodra Kumar and Ranjan, Ravi and Nalajala, Naresh and Reddy, Kasala Prabhakar and Gopinath, Chinnakonda S.} } @article {46876, title = {Cu-Ni bimetal integrated TiO2 thin film for enhanced solar hydrogen generation}, journal = {Solar RRL}, volume = {4}, year = {2020}, month = {MAY}, pages = {1900557}, type = {Article}, abstract = {

A series of non-noble Cu-Ni bimetallic catalysts is prepared with different molar proportions of metals. Of these bimetallic catalysts, 1 wt\% is subsequently integrated with titania P25. The catalysts are evaluated for solar hydrogen generation under 1 sun condition in both the powder and thin film forms. All the photocatalysts in the thin film exhibit an 8-24 times higher hydrogen yield (HY) compared with the corresponding particulate counterpart. The highest HY (41.7 mmol h(-1) g(-1)) is demonstrated for the photocatalyst Cu-Ni/TiO2 (CNT; 1:1 = Cu:Ni) in the thin film form, which is 24 times higher than that with its powder counterpart (1.75 mmol h(-1) g(-1)) and exceeds the performance of other Cu-Ni/TiO2 compositions. This enhanced activity in the thin film can be ascribed to improved absorption of visible light and an effective separation of photogenerated charge carriers at the interface of Cu-Ni/TiO2 leading to better charge carrier utilization.

}, keywords = {bimetals, energy conversion, Hydrogen, Photocatalysis, solar energy}, issn = {2367-198X}, doi = {10.1002/solr.201900557}, author = {Tudu, Bijoy and Nalajala, Naresh and Saikia, Pranjal and Gopinath, Chinnakonda S.} } @proceedings {47332, title = {Photocatalytic hydrogen production from H2S using nanostructured CNT blended CdZnS/Fe2O3 thin film on glass substrate}, volume = {1495}, year = {2020}, month = {MAR}, publisher = {IOP Publishing Ltd}, abstract = {

A co-precipitation method was employed to prepare the CNT blended CdZnS/Fe2O3\ photocatalyst. Using the powder photocatalyst, the thin film of CNT blended CdZnS/Fe2O3\ photocatalyst over a glass substrate was prepared using the drop-casting method. The obtained thin film was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDAX), photoluminescence (PL), and hydrogen production activity studies in order to obtain information on their structural, morphology, chemical composition, optical and hydrogen production efficiency. The hydrogen production activity of catalyst or effective conversion of H2S into hydrogen (H2) and sulfur (S) using thin-film photocatalyst was evaluated using a simulated sulfide solution. The results showed that 1 mg of CNT blended CdZnS/Fe2O3\ catalyst coated as thin film over glass substrate (4.69 cm2) showed the highest hydrogen production value of 3180 μmol h-1g-1; compared to that of 1 mg CNT blended CdZnS/Fe2O3\ powder of 2510 μmol h-1g-1. From the above results, it is concluded that the thin film form of photocatlyst produced more hydrogen than the powder form. This is attributed to the effective charge separation and increased specific surface area in thin film photocatalyst.

}, doi = {10.1088/1742-6596/1495/1/012035}, author = {Raja, M. Anthony and Vijayarengan, Preethi and Pal, Yash and Nalajala, Naresh and Gopinath, Chinnakonda} } @article {47600, title = {Aqueous methanol to formaldehyde and hydrogen on Pd/TiO2 by photocatalysis in direct sunlight: structure dependent activity of nano-Pd and atomic Pt-coated counterparts}, journal = {ACS Applied Energy Materials}, volume = {4}, year = {2021}, month = {NOV }, pages = {13347-13360}, type = {Article}, abstract = {In the present investigation, facet-controlled Pd nanoparticles with nanocube (Pd-NC) and truncated octahedron (Pd-TO) morphologies, and their counterparts with half-a-monolayer of atomic Pt coated (0.5 theta(Pt)-Pd-NC and 0.5 theta(Pt)-Pd-TO) surfaces were prepared. All of them were characterized and evaluated as cocatalyst after supporting them on commercial titania (P25) (Pd-NC/P25, Pd-TO/P25, 0.5 theta(Pt)-Pd-NC/P25, and 0.5 theta(Pt)-Pd-TO/P25) under direct sunlight and/or one sun conditions for the oxidation of methanol to formaldehyde along with solar hydrogen production. Pd-NC/P25 shows higher activity for hydrogen generation compared to Pd-TO/P25; however, activity reversal occurs with the above cocatalysts, but, after Pt-coating with further enhanced activity. The highest conversion of methanol (0.2 mu mol/h.mg) to 100\% selective formaldehyde was observed with 0.5 theta(Pt)-Pd-TO/P25, while other catalysts show significantly lower methanol conversion in the following order: 0.5 theta(Pt)-Pd-TO/P25 > 0.5 theta(Pt)-Pd-NC/P25 > Pd-NC/P25 > Pd-TO/P25. Pt-coated on (111) facets of Pd-TO simulates the activity associated as that of Pt(111) facets and demonstrating the highest and facet dependent activity. The present study is truly in resonance with exploiting the surface properties for heterogeneous catalysis, and highlights that less than a monolayer of Pt is sufficient to simulate the activity as that of bulk Pt. It is worth exploring this concept to other metals and substrates too.}, keywords = {heterogeneous catalysis, Nanomaterials, Oxidation, Photocatalysis, surface modification}, issn = {2574-0962}, doi = {10.1021/acsaem.1c03080}, author = {Nalajala, Naresh and Salgaonkar, Kranti N. and Chauhan, Inderjeet and Mekala, Siva Prasad and Gopinath, Chinnakonda S.} } @article {47589, title = {Electronically integrated mesoporous Ag-TiO2 nanocomposite thin films for efficient solar hydrogen production in direct sunlight}, journal = {Energy Technology}, volume = {10}, year = {2021}, month = {AUG}, pages = {2100356}, type = {Article}, abstract = {

The synthesis of mesoporous TiO2 by a solution-based assembly process and Ag/TiO2 nanocomposites is provided. The efficacy of Ag/TiO2 nanocomposite as photocatalyst in thin-film form is demonstrated for solar hydrogen generation in sunlight. Integration of Ag with TiO2 dramatically enhanced the H-2 production: with 1 wt\% Ag on TiO2 (TiAg-1), the H-2 yield was observed to be 4.59 mmol h(-1) g(-1), which is 2.3 (30) times larger than 0.5 wt\% Ag on TiO2. TiAg-1 shows 4.3 times higher activity in film form compared with its powder counterpart. High photocatalytic efficiency is attributed to the surface plasmon resonance effect of Ag, electronic integration of Ag with TiO2, and subsequent valence band broadening, large distribution of Ag nanoparticles and abundant Ag-TiO2 Schottky junctions, and the later minimizes electron-hole recombination. Interparticle mesoporous network increases necking and the high surface area offers easy accessibility of the reactants to a large number of active sites.

}, keywords = {heterogeneous catalysis, heterojunctions, plasmon effect, Silver, solar energy conversion, Solar hydrogen}, issn = {2194-4288}, doi = {10.1002/ente.202100356}, author = {Mani, Sunesh S. and Rajendran, Sivaraj and Nalajala, Naresh and Mathew, Thomas and Gopinath, Chinnakonda S.} } @article {47376, title = {Polyaryletherketone in energy conversion and storage devices - a highly tailorable material with versatile properties}, journal = {Polymer International}, volume = {70}, year = {2021}, month = {AUG}, pages = {1026-1037}, type = {Review}, abstract = {

Polymers have been a highly useful class of material for the last few decades owing to their ease of bulk production and fabrication. With the myriad of applications in day to day life, they have also found an important role in energy conversion and storage devices, not just as a housing material of the device but with an important role in the energy conversion process. Among the several polymers used in this area, polyaryletherketones (PAEKs) are one of the most versatile materials owing to their easy tailorability. The ether and ketone groups can be introduced in the main polymer chain in several ways to achieve the desired material properties. The main role of a polymer in an energy conversion device is that of a barrier to avoid the mixing of reactants and to selectively transport ions from one electrode to the other to maintain charge neutrality. The polymer membrane finds application in various electrochemical energy conversion devices such as fuel cells, lithium ion batteries, redox flow batteries, supercapacitors etc. The main focus of this work is to briefly review the extent of development in the PAEKs in various energy conversion and storage devices. (c) 2021 Society of Industrial Chemistry.

}, keywords = {electrolyte membrane, energy conversion and storage, fuel cells, lithium ion batteries, redox flow batteries, separator}, issn = {0959-8103}, doi = {10.1002/pi.6233, Early Access Date = APR 2021}, author = {Feroze Gooty Saleha, Wasim and Nalajala, Naresh and Neergat, Manoj} } @article {47702, title = {Rationally designed, efficient, and earth-abundant Ni-Fe cocatalysts for solar hydrogen generation}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {9}, year = {2021}, month = {OCT }, pages = {13915-13925}, type = {Article}, abstract = {Developing highly efficient and affordable catalysts for solar hydrogen (H-2) generation is crucial, and employing a cocatalyst from earth-abundant elements has a critical role to play. In this context, different compositions of earth-abundant Ni-Fe alloy (1:1, 1:3, and 3:1) have been prepared by hydrothermal method; subsequently, 1 wt \% of these Ni-Fe cocatalysts were integrated with TiO2-P25 and thoroughly characterized. The resultant catalysts have been evaluated for solar H-2 production, in powder and thin film forms, under one sun condition and in direct sunlight. Interestingly, all the catalysts in the thin film form exhibit superior hydrogen yield (HY), up to 27 times higher activity than its powder counterpart. Among the photocatalysts, Ni-Fe/TiO2 (3:1 = Ni/Fe; NFT31) composition exhibits the best HY in thin film (8.27 mmol.h(-1).g(-1)) and exceeds all other compositions of catalyst. It is also to be reported that HY measured for the powder form with 1 mg shows 3-17 times higher activity than that measured with 25 mg. This is mainly attributed to effective solar light absorption with a smaller amount of photocatalyst either spread over large area in a thin film form or well-dispersed in suspension forms. Furthermore, the enhanced activity obtained with Ni-Fe/TiO2 photocatalysts is also ascribed to strong electronic integration of Ni-Fe cocatalyst with TiO2 and higher performance obtained with a thin film is attributed to increased charge carrier generation and subsequent charge separation and effective utilization. A decrease in work function of TiO2 by 0.6 eV was observed after its integration with cocatalyst in NFT31.}, keywords = {Cocatalyst, Hydrogen, Ni-Fe alloy, solar energy, TiO2, water splitting}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.1c05158}, author = {Tudu, Bijoy and Nalajala, Naresh and Reddy, Kasala Prabhakar and Saikia, Pranjal and Gopinath, Chinnakonda S.} } @article {47101, title = {Scalable and thin film approach for solar hydrogen generation: a review on enhanced photocatalytic water splitting}, journal = {Journal of Materials Chemistry A}, volume = {9}, year = {2021}, month = {JAN}, pages = {1353-1371}, type = {Review}, abstract = {

Although nearly five decades of efforts have gone into solar water splitting (SWS), still success eludes and there is no big breakthrough till date. While huge importance is given either individually or concurrently to the three fundamental steps, namely, light absorption, charge carrier separation and diffusion and charge utilization at redox sites, many aspects that are practically helpful to improve the efficiency are not widely discussed and practised. Nonetheless, by adopting a number of small, but significant changes, solar hydrogen production can be enhanced. The present review discusses such different approaches employed for photocatalytic water splitting reported in the literature. For example, an increase of up to two orders of magnitude in solar hydrogen generation was observed with a film form compared to the particulate form of the same catalyst. Discussion on various approaches of enhanced hydrogen production under sunlight and one sun conditions is the main focus of this review, in particular with thin-film forms. The merits and demerits of thin film and particulate methods, respectively, are addressed in detail. Potential methods and successful stories on scalability are also discussed in the present review. In contrast to charge collection over a long distance in solar cell-based methods, a film-based method discussed shows that the local charge utilisation at a zero applied potential is an attractive feature for SWS. A comparison is provided between the PEC-WS and SWS for solar hydrogen generation, and how far we are from the reality to produce solar hydrogen on an industrial scale. We believe the presently practised diverse evaluation efforts may be truncated to fewer methods such as film-based evaluation and in a focussed manner to tackle the SWS issue towards sustainable production of solar hydrogen.

}, issn = {2050-7488}, doi = {10.1039/d0ta09619a}, author = {Gopinath, Chinnakonda S. and Nalajala, Naresh} } @article {48704, title = {Baby step in assembling and integrating the components of an artificial photosynthesis device with forced heterojunctions towards improved efficiency}, journal = {Journal of Materials Chemistry A}, volume = {11}, year = {2023}, month = {JUL }, pages = {15168-15182}, type = {Article}, abstract = {

How to achieve unassisted, economical, scalable, and sustainable artificial photosynthesis for liquid fuels/products with improved solar-to-fuel efficiency (STFE) to address a carbon-neutral economy remains a big question. To a large degree, the extent of charge separation at heterojunction interfaces and charge utilization determine the STFE. Towards this, BiVO3 is assembled from ionic-precursors into TiO2 pores, and integrated structurally and electronically with TiO2 on calcination as BiVO4 quantum dots (BVQDs). BVQDs in TiO2 (BVT) pores lead to an all-inorganic system with a sub-quadrillion number of heterojunctions in a 1 cm(2) device (contains similar to 25 mu g of BiVO4 (similar to 2.5 wt\%) in the nanopores of similar to 975 mu g of TiO2 (similar to 97.5 wt\%)) and facilitate artificial photosynthesis. We demonstrate 31-38\% STFE with a photon to chemical conversion turn over frequency (ToF(P2C)) of 2.73 s(-1) with a 1 cm(2) wireless BiVO4-TiO2 artificial leaf (BVT-AL) device for HCHO and CH3OH. The sequential nature of CO2 reduction to HCHO and then to CH3OH is evident from the reaction results. (CO2)-C-13 isotopic labeling experiments confirm that the input CO2 is the source for product formation. A large increase in the photocurrent density and incident photon-to-current efficiency (IPCE) of BVT, over 100\% for the BiVO4 photoanode in visible light, demonstrates and supports efficient visible light absorption, charge separation and migration to the redox sites. A device has been demonstrated to show sustainable activity in direct sunlight, and addresses scalability from 1 to 9 cm(2). Assuming no change (50\% decrease) in the STFE, a 6.74 m(2) device is expected to convert 1 (0.5) kg h(-1) CO2 into C1-oxygenates in sunlight. DFT calculations carried out with anatase TiO2 (101) and BiVO4 (121) interfaces support many of the experimental findings, including electron flow from the latter to the former, and interaction of the oxygen of TiO2 with BiVO4 and vice versa at the interface towards forced heterojunctions.

}, issn = {2050-7488}, doi = {10.1039/d3ta01850d}, author = {Salgaonkar, Kranti N. and Bajpai, Himanshu and Mhamane, Nitin B. and Nalajala, Naresh and Chauhan, Inderjeet and Thakkar, Kavita and Joshi, Kavita and Gopinath, Chinnakonda S.} } @article {48469, title = {Photocatalytic setup for in situ and operando ambient-pressure X-ray photoelectron spectroscopy at MAX IV Laboratory}, journal = {Journal of Synchrotron Radiation}, volume = {30}, year = {2023}, month = {MAY}, pages = {613-619}, type = {Article}, abstract = {

The Ambient-Pressure X-ray Photoelectron Spectroscopy (APXPS) endstation at the SPECIES beamline at MAX IV Laboratory has been improved. The latest upgrades help in performing photo-assisted experiments under operando conditions in the mbar pressure range using gas and vapour mixtures whilst also reducing beam damage to the sample caused by X-ray irradiation. This article reports on endstation upgrades for APXPS and examples of scientific cases of in situ photocatalysis, photoreduction and photo-assisted atomic layer deposition (photo-ALD).

}, keywords = {APXPS, photo-ALD, Photocatalysis, solar simulator}, issn = {0909-0495}, doi = {10.1107/S1600577523002801}, author = {Klyushin, Alexander and Ghosalya, Manoj and Kokkonen, Esko and Eads, Calley and Jones, Rosemary and Nalajala, Naresh and Gopinath, Chinnakonda S. and Urpelainen, Samuli} } @article {48800, title = {Possible handle for broadening the catalysis regime towards low temperatures: proof of concept and mechanistic studies with CO oxidation on surface modified Pd-TiO2}, journal = {Physical Chemistry Chemical Physics}, volume = {25}, year = {2023}, month = {AUG }, pages = {22040-22054}, type = {Article}, abstract = {

The present work demonstrates the effect of temperature-dependent surface modification (SM) treatment and its influence in broadening the catalysis regime with Pd-TiO2 catalysts prepared by various methods. Due to SM induced changes, a shift in the onset of CO oxidation activity as well as broadening of the oxidation catalysis regime by 30 to 65 K to lower temperatures is observed compared to the temperature required for virgin counterparts. SM carried out at 523 K for Pd-Photo-TiO2 exhibits the lowest onset (10\% CO2 production - T-10) and T-100 for CO oxidation at 360 and 392 K, respectively, while its virgin counterpart shows T-10 and T-100 at 393 and 433 K, respectively. The SMd Pd-TiO2 catalysts were investigated using X-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS) and atomic force microscopy (AFM). It is observed that diffusion of atomic oxygen into Pd-subsurfaces leads to SM and changes the nature of the surface significantly. These changes are demonstrated by work function (\& phi;), surface potential, catalytic activity, and correlation among them. UPS results demonstrate the maximum increase in \& phi; by 0.5 eV for Pd-Photo-TiO2 after SM, compared to all other catalysts. XPS study shows a moderate to severe change in the oxidation states of Pd due to atomic oxygen diffusion into the subsurface layers of Pd. Kelvin probe force microscopy (KPFM) study also reveals corroborating evidence that the surface potential increases linearly with increasing temperature deployed for SM up to 523 K, followed by a marginal decrease at 573 K. The \& phi; measured by KPFM and UPS shows a similar trend and correlates well with the changes in catalysis observed. Our results indicate that there is a strong correlation between surface physical and chemical properties, and \& phi; changes could be considered as a global marker for chemical reactivity.

}, issn = {1463-9076}, doi = {10.1039/d3cp01122d}, author = {Mhamane, Nitin B. B. and Panchal, Suresh and Kolekar, Sadhu K. K. and Ranjan, Ravi and Salgaonkar, Kranti N. N. and Burange, Anand S. S. and Nalajala, Naresh and Datar, Suwarna and Gopinath, Chinnakonda S. S.} } @article {48273, title = {Selective and generic photocatalytic oxidation of alcohol with Pd-TiO2 thin films: butanols to butanal/butanone with different morphologies of Pd and 0.5 theta(Pt)-Pd counterparts}, journal = {Chemistry-An Asian Journal}, volume = {18}, year = {2023}, month = {MAR}, type = {Article}, abstract = {

The present study reports on the photocatalytic oxidation of butanols to butanal/butanone using thin film form of facet-dependent nano-Pd supported on commercial TiO2 under one-sun condition and demonstrates the generic nature. Pd-nanocube (Pd-NC(100)), Pd-truncated octahedron (Pd-TO (100) and (111)), polycrystalline (Pd-PC), and their counterparts with half-a-monolayer Pt-coated on Pd (0.5 theta(Pt)-Pd)) have been used as co-catalyst. A potentially scalable thin film form of Pd/TiO2 photocatalyst, prepared by drop-casting method, has been employed to study oxidation of n-butanol, 2-butanol, and iso-butanol to corresponding aldehyde/ketone. 100\% selectivity is demonstrated to respective aldehyde/ketone with any catalyst used in the present study with varying degree of butanols conversion by NMR. 0.5 theta(Pt)-Pd-TO/TiO2 shows the highest conversion of 2-butanol to butanone (13.6\% in 4 h). Continuous 10 h of reaction with the most active 0.5 theta(Pt)-Pd-TO/P25 catalyst demonstrates 31\% conversion of 2-butanol to butanone, and catalyst recyclability has been demonstrated. The present protocol can be scalable to large scales to maximize the conversion in direct sunlight. Due to its generic nature, the current method can also be applied to many other alcohols and substrate molecules.

}, keywords = {energy conversion, Nanomaterials, Oxidation, Photocatalysis, Sustainability}, issn = {1861-4728}, doi = {10.1002/asia.202201239}, author = {Salgaonkar, Kranti N. and Kale, Sandip R. and Nalajala, Naresh and Mansuri, Sayana and Gopinath, Chinnakonda S.} }