Redox Replacement Reaction Research Articles

Improved morphological stability of NiFe2O4 via Sr doping for chemical looping hydrogen production

As a new hydrogen production technology, chemical looping hydrogen production has the advantage of internal CO2 separation. NiFe2O4 is considered as promising oxygen carrier material for chemical looping hydrogen production due to the high oxygen carrying capacity and low cost. However, rapid redox performance fading caused by structure degradation and interface instability in successive redox reactions that led fto poor stability, and seriously limited the practical application of NiFe2O4 in chemical looping hydrogen production. Herein, we reported a method for improving the morphological stability of NiFe2O4 through Sr doping. NiFe2O4 samples containing different SrO contents (2 wt%, 5 wt% and 8 wt%) were prepared by a simple mechanical mixing method. A series of characterization analysis results showed that adding an appropriate amount of Sr could significantly improve the microstructure, increase the oxygen vacancy concentration and inhibit the phase segregation of NiFe2O4. The NiFe-5Sr presented the largest BET surface area (24.63 m2/g) and highest concentration of oxygen vacancies (77.49 %). NiFe-0Sr and NiFe-2Sr experienced severe phase segregation during continuous cyclic reactions, resulting in significant surface sintering and deactivation. During 20 redox cycles, NiFe-5Sr presented the highest hydrogen yield (around 10 mmol/g) and stable surface morphology. The research results indicated that the optimal doping amount for SrO was 5 %.

Redox Concomitant Formation Method for Fabrication of Cu(I)-MOF/Polymer Composites with Antifouling Properties.

Marine biofouling, which is one of the technical challenges hindering the growth of the marine economy, has been controlled using cuprous oxide (Cu2O) nanoparticles due to the exceptional antifouling properties of Cu(I) ions. However, Cu2O nanoparticles have encountered bottlenecks due to explosive releases of Cu+ ions, high toxicity at elevated doses, and long-term instability. Here, we present a novel method called Redox Concomitant Formation (RCF) for fabricating a hierarchical Cu(I) metal-organic framework polypyrrole (Cu(I)-MOF/PPy) composite. This method enables in-situ phase transition via successive redox reactions that change the chemical valence state and coordination mode of Cu(II)-MOF, resulting in a new structure of Cu(I)-MOF while creating a PPy layer surrounded by the hierarchical structure. Owing to the steady release of Cu+ ions from the Cu(I) sites and photothermal properties of PPy, Cu(I)-MOF/PPy exhibits superior and broad-spectrum resistance to marine bacteria, algae, and surface-adhered biofilms in complex biological environments, as well as long-term stability, resulting in 100% eradication efficiency under solar-driven heating. Mechanistic insights into successive structural redox reactions and formation using the RCF method are provided in detail, enabling the fabrication of novel MOFs with the desired composition and structure for a wide range of potential applications.

Redox Concomitant Formation Method for Fabrication of Cu(I)−MOF/Polymer Composites with Antifouling Properties

AbstractMarine biofouling, which is one of the technical challenges hindering the growth of the marine economy, has been controlled using cuprous oxide (Cu2O) nanoparticles due to the exceptional antifouling properties of Cu(I) ions. However, Cu2O nanoparticles have encountered bottlenecks due to explosive releases of Cu+ ions, high toxicity at elevated doses, and long‐term instability. Here, we present a novel method called Redox Concomitant Formation (RCF) for fabricating a hierarchical Cu(I) metal–organic framework polypyrrole (Cu(I)−MOF/PPy) composite. This method enables in situ phase transition via successive redox reactions that change the chemical valence state and coordination mode of Cu(II)−MOF, resulting in a new structure of Cu(I)−MOF while creating a PPy layer surrounded by the hierarchical structure. Owing to the steady release of Cu+ ions from the Cu(I) sites and photothermal properties of PPy, Cu(I)−MOF/PPy exhibits superior and broad‐spectrum resistance to marine bacteria, algae, and surface‐adhered biofilms in complex biological environments, as well as long‐term stability, resulting in 100 % eradication efficiency under solar‐driven heating. Mechanistic insights into successive structural redox reactions and formation using the RCF method are provided in detail, enabling the fabrication of novel MOFs with the desired composition and structure for a wide range of potential applications.

Exceeding Three-Electron Reactions in Polyanionic Cathode To Achieve High-Energy Density for Sodium-Ion Batteries.

Activating multielectron reactions of sodium superionic conductor (NASICON)-type cathodes toward higher energy density remains imperative to boost their application feasibility. However, multisodium storage with high stability is difficult to achieve due to the sluggish reaction kinetics, irreversible phase transitions, and negative structural degradation. Herein, a kind of NASICON-type Na2.5V1.5Ti0.5(PO4)3/C (NVTP-0.5) hierarchical microsphere consisting of abundant primary nanoparticles is designed, realizing a reversible 3.2-electron reaction with high stability. The optimized NVTP-0.5 cathode demonstrates an ultrahigh discharge capacity of 192.42 mAh g-1, energy density of up to 497.3 Wh kg-1 at 20 mA g-1, and capacity retention ratio of 94.1% after 1000 cycles at 1 A g-1. Additionally, the NVTP-0.5 cathode delivers excellent tolerance to extreme temperatures while also achieving a high-energy density of 400 Wh kg-1 (based on the cathode mass) in a full-cell configuration. Systematic in situ/ex situ analysis results confirm the multisodium storage processes of NVTP-0.5 involving successive redox reactions (V2+/V3+, Ti3+/Ti4+, and V3+/V4+ redox couples) and reversible structure evolution (solid-solution and biphasic mechanisms), which contribute to the high capacity and excellent cycling stability. This work indicates that the rational regulation of components with different functions can unlock more possibilities for the development of NASICON-type cathodes.

(Invited) Electroless Cu, Pb and Ag Monolayer Deposition – Generality of an Electroless Monolayer Deposition Phenomenon

Recent progress in fuel cell catalysis has been enabled in great part by facile methods for catalyst monolayer synthesis based on surface limited redox replacement (SLRR) of underpotentially deposited (UPD) monolayers. Although this approach has been very effective, it has shown a limited applications in majority of heterogeneous gas phase catalysis problems where substrates are oxide based materials with very limited conductivity. In this talk we point out a new possibility for catalyst monolayer synthesis via SLRR on metal surfaces which are not part of a broadly conductive substrates such as metal nanoparticles imbedded in various oxide or zeolite supports. This is enabled by discovery of an electroless (E-less) Pb, Cu and Ag monolayer deposition phenomenon. Fundamentals of the E-less monolayer deposition are reviewed, and new data illustrating Cu and Ag monolayer deposition are presented. The focus is on emphasizing generality of the E-less monolayer deposition phenomenon, its self-termination and surface selectivity towards substrates at which Cu, Ag and Pb form UPD monolayer. Examples of the thin films and catalyst monolayer deposition via SLRR of E-less Cu, Ag and Pb monolayer are presented under the auspices of a newly developed two-step electroless atomic layer deposition protocol (E-less ALD)1.1) Electroless Pb Monolayer Deposition – Prelude for Further Advances in Catalyst Monolayer Synthesis via Surface Limited Redox Replacement Reaction”, K. Ahmadi, N. Dole, D. Wu, T. Salavati‐Fard, L. C. Grabow, F. C. Robles Hernandez, and S. R. Brankovic, ACS Catalysis, 11, 4650 (2021).

Successive redox modulation in an iron(ii) spin-crossover framework

Spin crossover behaviors were first modulated by successive redox reactions within an inverse-Hofmann-type metal–organic framework.

A High-Performance Quasi-Solid-State Aqueous Zinc-Dual Halogen Battery.

Aqueous zinc-based batteries are promising candidates for the grid-scale energy storage owing to their nonflammability, ecofriendliness, and low cost. Nevertheless, their practical applications are hindered by the relatively low capacity and energy density. Herein, we develop a quasi-solid-state aqueous zinc-dual halogen battery composed of freestanding carbon cloth-iodine cathode and in situ prepared concentrated aqueous gel electrolyte. The freestanding composite cathode and aqueous gel electrolyte can afford iodine source and bromide ions, respectively, thus activating the I-/I0/I+ reaction by forming [IBr2]- interhalogen. Furthermore, the conversion reaction of Br-/Br0 in [IBr2]- interhalogen is stimulated due to the catalytic effect of iodine. Therefore, this rationally designed aqueous dual halogen conversion chemistry enables three successive redox reactions (i.e., I-/I0, I0/I+, and Br-/Br0). Additionally, the LiNO3 additive and acrylamide (AM)-based polymer matrix not only stabilizes the anode/electrolyte interface but also restrains the side reactions and dissolution/diffusion of active species. Consequently, the as-assembled aqueous zinc-dual halogen battery exhibits high areal capacity and energy density.

High-performance aqueous rechargeable Zn-Ag and Zn-Ag/air hybrid batteries based on Ag nanobelts as highly stable bifunctional electrode

The Zn-Ag and Zn-Ag/air hybrid batteries are challenged by the low conductivity and capacity of Ag electrode materials. How to further optimize and tune the surface electronic structure of Ag nanomaterials has become an important topic in the improvement of Ag electrode materials. Herein, the silver nanobelts (Ag NBs) materials were prepared by a fast and simple redox replacement reaction. The special nanobelts structure, with the key surface features of the gully-like morphology, raised Ag mounds and superlattice fringes, are beneficial to tune the surface electron structure and thereby increase the conductivity and electrochemical performance of Ag NBs. As a consequence, the assembled Zn-Ag battery exhibits favorable electrochemical performance in view of the specific capacity of 380.9 mAh gAg−1. In addition, the hybrid Zn-Ag/air battery shows two-step voltage plateaus of 1.83 and 1.55 V in the Zn-Ag reaction, as well as a voltage plateau of 1.23 V corresponding to the Zn-air reaction. The hybrid battery maintains a high energy efficiency of 76.9% and high rate capabilities, demonstrating an excellent energy-saving feature of this battery. The insights gained from this work may be beneficial for designing the highly-efficient Ag catalysts for electrochemical energy storage.

Structural Evolution, Redox Mechanism, and Ionic Diffusion in Rhombohedral Na2FeFe(CN)6 for Sodium-Ion Batteries: First-Principles Calculations

Prussian blue analogs (Na2FeFe(CN)6) have been regarded as potential cathode materials for sodium-ion batteries (SIBs) due to their low-cost iron resources and open framework. Herein, the detailed first-principles calculations have been performed to investigate the electrochemical properties of Na x FeFe(CN)6 during Na ion extraction. The material undergoes a phase transition from a dense rhombohedral to open cubic structure upon half-desodiation, which is resulted from competition of the Na−N Coulomb attraction and d−π covalent bonding of Fe−N. The analyses on the density of states, magnetic moments and Bader charges of Na x FeFe(CN)6 reveal that there involve in the successive redox reactions of high-spin Fe2+/Fe3+ and low-spin Fe2+/Fe3+ couples during desodiation. Moreover, the facile three-dimensional diffusion channels for Na+ ions exhibit low diffusion barriers of 0.4 eV ∼ 0.44 eV, which ensures a rapid Na+ transport in the Na x FeFe(CN)6 framework, contributing to high rate performance of the battery. This study gives a deeper understanding of the electrochemical mechanisms of Na x FeFe(CN)6 during Na+ extraction, which is beneficial for the rational design of superior PBA cathodes for SIBs.

Viologen Derivatives in Deep Eutectic Solvents for Energy Storage

Redox flow batteries (RFBs) serve as one of the most promising battery technologies to meet the grid-scale energy storage requirements, owing to their scalable nature and acceptable redox chemistry. To achieve economical and sustainable energy storage, there has been a rapid transition from redox-active inorganic materials to the earth-abundant and tunable redox-active organic compounds for RFBs. Among explored redox-active organic materials, viologen derivatives show promise for battery applications due to their two successive redox reactions and low cost. Taking advantage of both redox reactions, however, may not be possible in aqueous electrolytes due to the insolubility of the charge-neutral viologen in aqueous solutions.1 Deep eutectic solvents (DESs) can offer an inexpensive electrolyte for energy storage which could potentially solve the solubility issues associated with these materials.2 Owing to their low vapor pressure, DESs can be also utilized at elevated temperatures for lower viscosity and enhanced conductivity.3 In an attempt to identify a high-concentrated and reversible redox-active DES, the electrochemical properties and solubility of methyl, ethyl, and benzyl viologens in choline chloride (ChCl) and ethylene glycol (EG) (1:4 molar ratio) mixture were investigated. To better qualify these redox-active molecules as an anolyte material for RFBs, the redox reactions were studied to assess the redox reversibility, the potential separation between the consecutive electron transfer reactions, and the redox kinetics. The electron-transfer rate constants were estimated using linear sweep voltammetry (LSV) at a glassy carbon rotating-disk electrode in a three-electrodes configuration cell. Diffusion coefficients were also calculated from the steady-state diffusion-limited current using the rotating-disk electrode as well as a microelectrode. Elucidating the kinetic parameters, diffusion coefficients, and transport properties of the viologen derivatives in DESs will bring insight into designing a concentrated redox-active DES for energy storage. B. Hu and T. L. Liu, J. Energy Chem., 27, 1326 (2018).B. Chen, S. Mitchell, N. Sinclair, J. Wainright, E. Pentzer, and B. Gurkan, Mol. Syst. Des. Eng., 5, 1147 (2020).N. S. Sinclair, D. Poe, R. F. Savinell, E. J. Maginn, and J. S. Wainright, J. Electrochem. Soc., 168, 020527 (2021).

(Keynote) Fundamental Origin of the Electroless Pb Monolayer Deposition and Its Implications for Electroless Atomic Layer Deposition

In this talk, we point out a novel opportunity for catalyst monolayer and core-shell structures synthesis via surface limited redox replacement (SLRR) reaction. It is enabled by discovery of an electroless Pb monolayer deposition phenomenon whose fundamentals and practical aspects are presented. The particular benefit of this synthesis approach is for metal substrates which are not part of a broadly conductive supports such as metal nanoparticles imbedded in various oxides or zeolites. Examples of the catalyst monolayer deposition via SLRR of electrolesslly deposited Pb monolayer are presented under the auspices of a two-step electroless atomic layer deposition process (e-less ALD). Each cycle of the e-less ALD produces a precise submonolayer amount of catalyst deposit demonstrating its potential for a broad range of applications including synthesis of the oxide-supported catalyst core-shell structures or surface selective metallization in microelectronics. Figure 1

Electroless Pb Monolayer Deposition—Prelude for Further Advances in Catalyst Monolayer Synthesis via Surface Limited Redox Replacement Reaction

We point out a novel opportunity for catalyst monolayer and core–shell structures synthesis via the surface limited redox replacement (SLRR) reaction. It is enabled by discovery of an electroless P...

Reaction performance of Ce-enhanced hematite oxygen carrier in chemical looping reforming of biomass pyrolyzed gas coupled with CO2 splitting

Hematite enhanced by CeO2 were investigated in chemical looping reforming (CLR) coupled with CO2 splitting to achieve high quality synthesis gas and recycle CO2 into CO. CeO2, Fe2O3 and CeFeO3 solid solution generated from integration of Fe3+ and CeO2 lattice were detected in mixed oxygen carriers as major components. Owing to the charge compensation and oxygen defects formation in lattice rearrangement, CeFeO3 solid solution contributed to promoting oxygen mobility and creating oxygen vacancies. Fe2O3 particles helped provide oxygen spillover pathway from subsurface to surface and improve lattice oxygen transfer through direct contact with the surface of CeFeO3 solid solution. CeO2 enhanced metallic interaction and catalytic oxidation reactivity. The highest gas product amount and H2/CO in CLR process increased by 43.46% and 51.31%, respectively. Also, the instantaneous CO productivity of 2.47 mmol/min/g with 86.13% CO2 conversion was realized in CO2 splitting. Reaction parameters including temperature, CeO2 content and MCO2/mOC indicated positive correlation with CO productivity. The mixed oxygen carrier maintained its reactivity and stability after 15 cycles reaction following the pathway of Ce2O3/Fe2O3/CeFeO3→Ce2O3/Fe→CeFeO3/CeO2/Fe3O4, though sintering behavior was observed in reacted sample. Fe–Ce interactions and oxygen mobility were improved by successive redox reactions, which can offset the negative effects of sintering.

Electrosynthesis and characterization of PdIr using electrochemical atomic layer deposition for ethanol oxidation in alkaline electrolyte

This work reports Pd and PdIr thin films electrodeposition via surface limited redox replacement reaction using electrochemical atomic layer deposition technique. Cyclic voltammetry (CV) showed Pd and PdIr voltammetric signatures confirming the successful utilization of Cu as sacrificial metal for Pd and Ir ions. The resulting deposits were further characterized using XRD, EDS, XPS, SEM and AFM, confirming their structural morphology and surface roughness. The catalytic activity of the thin films towards the oxidation of ethanol was determined using CV. PdIr showed a more negative onset potential and higher current (−0.423 V; 0.664 mA) than Pd (−0.402 V; 0.494 mA) thin film, indicating a more catalytic behavior. Further, PdIr showed a higher if/ib ratio of 1.094 than Pd (if/ib = 0.94) indicating higher tolerance to poisoning by ethanol intermediates than Pd. Moreover, chronoamperometry (CA) confirmed that the addition of Ir to Pd improves the stability of the PdIr film. The resultant behaviour was also confirmed by EI spectroscopy with smaller Rct = 0.23 (kΩ) for PdIr than that of Pd; Rct = 14.8 (kΩ) when.Subjected at a fixed potential of −0.2 V. The higher catalytic activity of PdIr towards EOR makes it a promising candidate as electrocatalyst for alkaline direct ethanol fuel cell (DEFCs) than Pd.

Electrochemical atomic layer deposition of cadmium telluride for Pt decoration: Application as novel photoelectrocatalyst for hydrogen evolution reaction

Metal-chalcogenide nanomaterials, as compared to their wide bandgap counterparts, are particularly attractive photoelectrocatalytic materials for the conversion of solar energy into chemical energy under visible-light irradiation. In this study, the thin layer of CdTe was deposited on the surface of Au/ITO electrode using electrochemical atomic layer deposition. Deposition process was performed through the alternate under potential deposition of the Te and Cd elements with a monolayer at a time, respectively. The images of scaning electron microscopy (SEM) indicated that nanoparticles of CdTe well dispersed on Au/ITO with an average particle size about 15 nm. The results of energy dispersive analysis by X-rays (EDAX) confirmed the off-stoichiometric CdTe layer, which lead to Cd-rich CdTe because of tellurium vacancies in the deposition potential. The resulting Cd-rich CdTe/Au/ITO electrode was used for preparation of Pt/CdTe/Au/ITO by redox replacement reaction between Pt2+ and Cd excess in CdTe layer to form 1.76 wt% of Pt element which uniformly distributed on the surface of CdTe/Au/ITO. Chronoamperometric tests in sodium sulfide solution exhibited that the Cd-rich CdTe layer had n-type semiconductivity whereas the Pt/CdTe layer showed p-type semiconductivity. The Pt/CdTe/Au/ITO electrode showed higher photoelectrocatalytic activity for the HER as compared to a commercial Pt/C on Au/ITO. The onset potential for HER is almost similar and the overpotential at −10 mA cm−2 is 160 mV more positive on Pt/CdTe/Au/ITO under light illumination with respect to Pt/C/Au/ITO. The long-term stability tests under illumination in acidic solution revealed that Cd-rich CdTe and Pt/CdTe layeres have extremely high stablity for HER compared to Pt/C. The higher photocatalytic activity on Pt/CdTe/Au/ITO electrode for HER is attributed predominantly to the synergistic effect of Pt, which not only serves as co-catalysts for promoting electron transfer to the electrocatalyst-electrolyte interface, but also accelerates the HER.

Efficiently Engineering Cu-Based Oxide by Surface Embedding of Ce for Selective Catalytic Reduction of NO with NH3

Deliberately engineering oxide composites on constructing and manipulating interactive structures particularly in surface layers was highly desirable for heterogeneous catalysis. Herein, upon the redox replacement reaction between Ce(IV) precursor (Ce(NO[Formula: see text] and Cu2O nano-substrate, an attempt to directly engineer the surface structure of Cu-based substrate was performed by the Ce(IV)–Cu2O etching-embedding process, then the obtained powders were thermo-treated to get a series of Ce–O–Cu catalysts with different Ce:Cu molar ratios for NH3selective catalytic reduction (NH3-SCR) of NO. Characterized by ICP-OES, XRD, Raman, XPS, SEM, BET, H2-TPR, NO- and NH3-TPD measurements, it was demonstrated that the Cu–O–Ce catalysts were structured as CuO matrix with an interactive surface composed by co-present Cu(I)–Cu(II) and Ce(III)–Ce(IV) species, even the introduction of Ce was confined in a quite low loading range (0.83–2.3[Formula: see text]wt.%); such a surface exhibited the distinct synergistic effect with positively manipulated physical-chemistry properties such as active site distributions, redox features and surface reactivity compared to pure CuO and traditional Cu–Ce composite catalyst, leading to attractive catalytic performance such as [Formula: see text]% NO conversion with [Formula: see text]% N2selectivity and the two-fold TOF enhancement versus traditional catalysts, even SO2was present in reactant mixture on well-manipulated catalyst (Ce loading at 1.6[Formula: see text]wt.%) These results indicated that the etching-embedding strategy illuminated in this work could be referred as a feasible method to directly engineer and construct interactive oxide composite surface for advanced application as well as current efficient Ce–O–Cu catalytic interface for heterogeneous catalysis.

Strain Effect on Electrolytic Hydrogen Isotope Separation

The effect of strain in Pt and Pd monolayer catalyst is explored for electrolytic hydrogen isotope separation. Positive/negative strain increases/decreases strength of adsorbed hydrogen bond in overpotential region where recombination of hydrogen atoms is the rate determining step in hydrogen evolution reaction. As a result, the increased/decreased hydrogen isotope separation efficiency of Pt and Pd monolayers is expected as compared to bulk Pt and Pd. The positive/negative strain rises/lowers diffusion barrier for adsorbed hydrogen atoms. This effect favors/retards recombination of isotopes with smaller mass. As the surface is stretched/compressed, the neighboring adsorption sites separate/approach each other which affects heavier hydrogen isotopes more/less and results in their lower/higher probability for recombination. All these fundamental consideration indicate that Pt and Pd monolayers with different level of strain should have much different separation factors than corresponding bulk electrodes. To study described effects, Pt and Pd monolayers we synthesized electrochemically on Au(111) and Ru(0001) electrodes each yielding qualitatively different strain levels (Au-positive, Ru-negative). Pd monolayers are synthesized using electrodeposition[1] while Pt monolayers were synthesized using deposition via surface limited redox replacement reaction[2]. The adsorption strength of hydrogen isotopes is studied by infra-red spectroscopy. These results will are input in our classical models for isotope separation[3] and to our DFT calculations. The calculated ratio between the rates of hydrogen and deuterium recombination and separation factors for Pt and Pd monolayers and corresponding bulk electrodes are compared to experimentally measured ones. The following discussion is focused on understanding and quantification of strain effects on separation efficiency of Pt and Pd monolayers. [1] H. –F. Waibel, M. Kleinert, L. A. Kibler, and D. M. Kolb, Electrochim. Acta, 47, 1461 (2002). [2] S. R. Brankovic, J. X. Wang and R.R. Adzic, Surface Science, 474, L173 (2001). [3] B. E. Conway, Proceedings of The Royal Society of London, A. Mathematical and Physical Sciences, 247, 400 (1958).

Production of hydrogen and syngas using chemical looping technology via cerium-iron mixed oxides

Chemical looping based on steam reforming of methane was used to co-generate syngas (with H2/CO ratio of 2) and hydrogen without purification processes. Chemical precipitation method was used to prepare CeO2-Fe2O3 combined oxides with different Fe/Ce ratios as the oxygen carriers. The oxygen carriers were tested in the fixed bed micro reactor to investigate the reactivity of the prepared samples in methane conversion (reduction reaction) and water splitting (oxidation reaction) steps at different operating temperatures (700–900 °C). It was found that the Fe-Ce-3 oxygen carrier (Fe/Ce = 1) showed the best performance among the other ones. Also, the performance of the Fe-Ce-3 was evaluated at 850 °C in 10 repetitive redox cycles. It showed a durable production of syngas and hydrogen without significant deactivation for the successive redox reactions.

Electroless Deposition of Pb Monolayer: A New Process and Application to Surface Selective Atomic Layer Deposition.

The present work demonstrates an electroless (e-less) deposition of Pb monolayer on Au and Cu surface whose morphology and properties resemble its underpotentially deposited counterpart. Our results and analysis show that the e-less Pb monolayer deposition is a surface selective, surface controlled, self-terminating process. Results also show that the electroless Pb monolayer deposition is enabling a phenomenon for new deposition method called "electroless atomic layer deposition" (e-less ALD). Here, the e-less Pb monolayer serves as reducing agent and sacrificial material in surface limited redox replacement reaction with noble metal ions such as Pt n+, i.e., Pt deposition. The e-less ALD is highly selective to the metal substrates at which Pb forms the e-less monolayer. The full e-less ALD cycle leads to an overall deposition of a controlled amount of the noble metal. Repetition of the two-step e-less ALD cycle an arbitrary number of times leads to formation of a highly compact, smooth, and conformal noble metal thin film with applications spanning from catalyst synthesis to semiconductor technology. The process is designed for (but not limited to) aqueous solutions that can be easily scaled up to any size and shape of the substrate, deeming its wide applications.

Non-noble metallic nanoparticles supported on titania spheres as catalysts for hydrogen generation from hydrolysis of ammonia borane under ultraviolet light irradiation

Herein, a report on non-noble metal (Ni, Co, Cu, and their combination) nanoparticles (NPs) supported on TiO2 spheres as catalysts for hydrogen generation via hydrolysis of ammonia borane (NH3BH3, AB) is provided. The TiO2 spheres were prepared through a template method by using polystyrene (PS). The metallic nanoparticles were synthesized by a redox replacement reaction. The structure, morphology, and chemical composition of the obtained samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy dispersive X-ray spectroscopy (EDX), and X-ray Photoelectron Spectroscopy (XPS). The characterization results showed that the metallic nanoparticles were well dispersed on the TiO2 supports. The catalytic activity toward the hydrolysis of AB was found to correlate well with the amount of metallic elements in catalysts while for the multicomponent phases, a synergistic effect was noticed. Theoretical calculations revealed that Ni, Co, and Cu atoms significantly influenced the electronic behavior of TiO2 and thereby, the catalytic properties of the materials.