Metal-oxide Interactions Research Articles

Effective synergistic interaction between InZnZrOx ternary metal oxides and SAPO-34 molecular sieve catalysts for CO2 hydrogenation to light olefins

The synergistic interaction of metal oxides with molecular sieves is essential for the catalytic hydrogenation of carbon dioxide (CO2) into light olefins (C2=–C4=) over bifunctional tandem catalysts. Herein, a series of In2O3-doped InZnZrOx (IZZ) ternary metal oxides was prepared and physically mixed with SAPO-34. The bifunctional catalyst was used in the direct conversion of CO2 to light olefins. The relationship between IZZ oxide structures prepared using different methods and the catalytic performance of bifunctional catalysts was investigated. Moreover, the migration of InOx in ternary metal oxides was revealed. Results revealed that for IZZ oxides prepared via precipitation coating and impregnation, InOx species migrated to the SAPO-34 surface during thermocatalytic reaction due to the dispersion of In2O3 on the ZnZrOx surface and its weak interaction with ZnZrOx. This led to the neutralization of acid centers on SAPO-34 by InOx, thereby destroying the synergistic interaction between the oxides and SAPO-34, resulting in a large amount of unneeded methane and poor light olefin selectivity. However, the co-precipitated IZZ-CP oxides exhibited a ternary solid solution structure and inhibited the migration of InOx. This enhanced CO2 and H2 activation, affording more formate (HCOO*) and methoxide (CH3O*) intermediates that strengthened the synergistic interaction between the oxides and molecular sieves. After optimizing the In2O3 doping amount in IZZ-CP oxide and the reaction conditions, the IZZ-CP/SAPO-34 bifunctional catalyst achieved 17.9 % CO2 conversion, 80.1 % C2=–C4= selectivity, only 7.6 % methane and 44.6 % CO selectivity. It also maintained excellent catalytic stability without significant deactivation after continuous reaction for 80 h.

Synergistic removal of NO and CO in industrial waste gas by Fe-modified Cu/TiO2 catalysts: The synergistic effect of metal oxides interaction

NH3-based selective catalytic reduction (NH3-SCR) combined with carbon monoxide (CO) catalytic oxidation is a productive way to synergistically remove nitrogen oxides (NOx) and CO from industrial waste gas. Catalyst is the undoubtedly centerpiece of the synergistic removal technology, which has aroused tremendous attention. Herein, in this investigation a variety of Cu/TiO2 catalysts modified by various metal oxides were prepared by impregnation method, and the excellent synergistic removal performance of Fe-modified Cu/TiO2 catalyst was observed. The Cu/TiO2 catalyst with a 7 wt% Fe doping amount exhibited the highest NO and CO removal efficiency (86 % for NO at 300 °C and over 98 % for CO from 300 ∼ 400 °C). Through a series of characterization techniques, it was discovered that Cu and Fe oxides interacted to evenly distribute them throughout the surface of TiO2 support, resulting in smaller particle size and abundant variable valence species (Cu+/Cu2+ and Fe2+/Fe3+) to enhance the redox performance of the catalysts. Moreover, the creation of additional surface chemisorbed oxygen, the adsorption of NO and CO, and the improvement of surface acidity were all facilitated by the electron transfer between various Cu and Fe species. In addition, in-situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTS) results revealed the interaction between NH3-SCR and CO oxidation. This study proposes a viable approach to develop efficient catalysts for the synergistic removal of NO and CO in industrial applications.

Understanding the morphology and chemical activity of model ZrOx/Au (111) catalysts for CO2 hydrogenation

In this study, the growth of ZrOx on Au (111) was investigated using scanning tunneling microscopy (STM) and synchrotron-based ambient pressure X-ray photoelectron spectroscopy (AP-XPS). Nanostructures of ZrOx (x = 1,2) at the sub-monolayer (≤ 0.3 ML) level were prepared by vapor depositing Zr metal onto Au (111) followed by oxidation with O2 or CO2. At low coverages of the admetal (< 0.05 ML), the formed ZrOx nanostructures were dispersed randomly on the terraces and steps of the Au(111) substrate. Strong oxide-metal interactions prevented the formation of islands of zirconia. The ZrOx nanostructures displayed a reactivity towards CO2 and H2 not seen for bulk zirconia. C 1 s AP-XPS results indicated that CO2 molecules adsorbed on Zr/ZrOx/Au(111) surfaces could undergo partial decomposition on Zr (CO2, gas → COgas + Oads), or react with oxygen sites from ZrOx to yield carbonates (Zr-CO3, ads). After exposing ZrO2/Au (111) surfaces to 1:3 mixtures of CO2:H2, the formation of HCOO, CO3, and CH3O was detected in AP-XP spectra. These chemical species decomposed at temperatures in the range of 400‒600 K, making them possible reaction intermediates for methanol synthesis.

Electronic Oxide-Metal Strong Interactions (EOMSI) Localized at CeOx-Ag Interface.

Electronic oxide-metal strong interactions (EOMSI) refer to the electronic oxide-metal interactions (EOMI) between oxide adlayers and underlying metal substrate that is strong enough to stabilize supported oxide adlayers in a low-oxidation state, which individually is not stable under an ambient condition, from high temperature oxidation in air to a certain extent. Herein we report the deposition and electronic structure of CeOx adlayers on capping ligand-free cubic Ag nanocrystals, i.e., CeOx/Ag inverse catalysts. The EOMI occur via the charge transfer from Ag substrate to CeOx adlayers in the CeOx/Ag inverse catalyst, and the EOMSI are observed in the CeOx/Ag inverse catalyst with the average thickness of CeOx adlayers about 0.9 nm to exclusively form Ce2O3 adlayers stable against oxidation at 400 °C. As the thickness of CeOx adlayers increases, ceria adlayers with oxygen vacancies (CeO2-x) emerge and grow in the CeOx/Ag inverse catalysts, and the Ce3+/Ce4+ ratio decreases. Catalytic performance of CeOx/Ag inverse catalysts in the CO oxidation reaction is closely linked with the thickness and electronic structure of CeOx adlayers. These results demonstrate that the EOMSI and EOMI in the oxide/metal inverse catalysts are localized at the oxide-metal interface and sensitively vary with the thickness of oxide adlayers, offering a strategy of thickness engineering to tune electronic structures of oxide adlayers in oxide/metal inverse catalysts.

From Methane to Methanol: Pd-iC-CeO2 Catalysts Engineered for High Selectivity via Mechanochemical Synthesis.

In the pursuit of selective conversion of methane directly to methanol in the liquid-phase, a common challenge is the concurrent formation of undesirable liquid oxygenates or combustion byproducts. However, we demonstrate that monometallic Pd-CeO2 catalysts, modified by carbon, created by a simple mechanochemical synthesis method exhibit 100% selectivity toward methanol at 75 °C, using hydrogen peroxide as oxidizing agent. The solvent free synthesis yields a distinctive Pd-iC-CeO2 interface, where interfacial carbon (iC) modulates metal-oxide interactions and facilitates tandem methane activation and peroxide decomposition, thus resulting in an exclusive methanol selectivity of 100% with a yield of 117 μmol/gcat at 75 °C. Notably, solvent interactions of H2O2 (aq) were found to be critical for methanol selectivity through a density functional theory (DFT)-simulated Eley-Rideal-like mechanism. This mechanism uniquely enables the direct conversion of methane into methanol via a solid-liquid-gas process.

Electrochemical oxidation of Florfenicol in aqueous solution with mixed metal oxide electrode: Operational factors, reaction by-products and toxicity evaluation

Veterinary antibiotics have become an emerging pollutant in water and wastewater sources due to excess usage, toxicity and resistance to traditional water and wastewater treatment. The present study explored the degradation of a model antibiotic- Florfenicol (FF) using electrochemical oxidation (EO) with Ti–RuO2/IrO2 anode. The anode material was characterized using SEM-EDS studies expressing stable structure and optimal interaction of the neighboring metal oxides with each other. The EDS results showed the presence of Ru, Ir, Ti, O and C elements with 6.44%, 2.57%, 9.61%, 52.74% and 28.64% atomic weight percentages, respectively. Optimization studies revealed pH 5, 30 mA cm−2 current density and 0.05 M Na2SO4 for 5 mg L−1 FF achieved 90% TOC removal within 360 min treatment time. The degradation followed pseudo-first order kinetics. LC-Q-TOF-MS studies revealed six predominant byproducts illustrating hydroxylation, deflourination, and dechlorination to be the major degradation mechanisms during the electrochemical oxidation of FF. Ion chromatography studies revealed an increase in Cl−, F− and NO3− ions as treatment time progressed with Cl− decreasing after the initial phase of the treatment. Toxicity studies using Zebrafish (Danio rerio) embryo showed the treated sample to be toxic inducing developmental disorders such as pericardial edema, yolk sac edema, spinal curvature and tail malformation at 96 h post fertilization (hpf). Compared to control, delayed hatching and coagulation were observed in treated embryos. Overall, this study sets the stage for understanding the effect of mixed metal oxide (MMO) anodes on the degradation of veterinary antibiotic-polluted water and wastewater sources using electrochemical oxidation.

Migration roles of different oxygen species over Cu/CeO2 for propane and soot combustion

Determining the migration rules of oxygen species in catalytic combustion, especially for catalysts composed of transition metal oxides, is essential yet challenging. This study hydrothermally synthesized nanosphere-structured cerium dioxide (CeO2) and its copper-loaded catalysts (Cu/CeO2) to identify the distinct functions of superficial oxygen species (O) and lattice oxygen (O2–). The presence of Cu-Ce solid solution at the Cu/CeO2 interface lowered the apparent activation energy for the catalytic combustion of propane and soot. The catalytic combustion of propane followed the Mars-van Krevelen mechanism, with O2– serving as the dominant reactive phase while O played a subordinate role. The solid–solid reaction between soot and superficial oxygen of the catalyst was responsible for catalyzed soot combustion. The O species produced by surface defective sites exhibited higher activity than O2–, which drained easily at the beginning of the reactions. The isotopic oxygen exchange tests revealed the mechanism of metal oxide (CuO/CeO2) interactions for active oxygen species migration, with the results demonstrating the solid solution at the phase interface as portholes for oxygen migration, thus increasing oxygen mobility between the gaseous phase and the surface by lowering the migration activation energy. In situ, infrared results showed that the reaction path of soot catalytic combustion was single, without any intermediate production formation, compared to multiple paths in the propane oxidation process. This study provided an easily implemented and widely applicable method, which deepens our understanding of the characterization of the function and migration of predominant oxygen species in diverse combustion reactions involving oxide-based catalysts. Additionally, this study clarified differences and similarities between the reaction mechanisms of solid–solid and solid–gas catalysis.

Ternary Zn-Ce-Ag catalysts for selective and stable electrochemical CO2 reduction at large-scale

Catalyst materials with high stability and selectivity, based on inexpensive materials, are vital for practical electrochemical carbon dioxide (CO2) reduction (ECR). In this study, we report ternary Zn-Ce-Ag catalysts for selective and stable CO2-to-CO conversion at high current densities on a large scale. We found that ZnO catalysts are relatively selective for CO2-to-CO conversion, but are only stable for less than 20 h at current densities over 100 mA cm−2 due to the reduction of the Zn oxide phase, along with the ECR. Combining ZnO with CeO2 significantly improves the stability of the catalysts, maintaining a CO Faradaic efficiency (FECO) of 80 % for 100 h at the current density of 200 mA cm−2. By introducing a small amount of silver (<10 wt%) to form ternary Ag-Ce-Zn catalysts, both CO selectivity and stability are significantly improved: the developed catalysts exhibit a high FECO of 90 % at 200 mA cm−2 and are stable for 200 h. We attribute the enhanced CO2-to-CO conversion efficiency to the abundance of stable interfacial areas of various metal-oxide interactions, which are critical for ECR. To demonstrate the potential for practical application, we performed the ECR in a large electrochemical cell, with an active surface area of 100 cm2. The system delivers a FECO of 90 % at 200 mA cm−2 for an extended operation time of 200 h.

Highly transparent and efficient Pt/CeOx counter electrodes for bifacial dye-sensitized solar cells

In this research, we introduce a pioneering approach for enhancing the electrocatalytic performance of counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) by synthesizing Pt/CeOx hybrid nanocatalysts through a refined polyol reduction technique. This method facilitates the accurate production of Pt nanoparticles supported on ceria, leveraging their strong metal-oxide interactions. X-ray photoelectron spectroscopy (XPS) was employed to confirm the co-presence of both metallic and oxidized states of Pt, as well as the mixed valence states of ceria within these nanostructures. The electrocatalytic behavior of these nanocatalysts was rigorously evaluated using cyclic voltammetry (CV), Tafel polarization analyses, and electrochemical impedance spectroscopy (EIS). We identified an optimal Pt/Ce ratio of 1:0.1, which significantly enhanced the kinetics of the iodine reduction reaction (IRR), a crucial factor for efficient DSSC operation. Photovoltaic testing under one-sun AM 1.5 G conditions demonstrated that DSSCs with the optimized Pt/CeOx CEs exhibited a 10 % increase in power conversion efficiency (PCE) comparted to control cells. This study highlights the effectiveness of Pt/CeOx hybrid nanocatalysts in improving bifacial DSSC performance, combining the catalytic strengths of platinum with the unique properties of ceria.

Enhanced Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol over Silica-Coated Pt-CoxOy Hybrid Nanoparticles.

Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) is difficult due to the intrinsic difficulty with thermodynamically easier hydrogenation of C═C bonds. In this work, Pt-CoxOy hybrid nanoparticles encapsulated in mesoporous silica nanospheres (Pt-CoxOy@mSiO2) were synthesized by a sol-gel method, which showed greatly improved COL selectivity for hydrogenation of CAL. At 80 °C and 1.0 MPa of H2, Pt-CoxOy@mSiO2 achieved a CAL conversion of 98.7% with a COL selectivity of 93.5%. In contrast, Pt@mSiO2 yields 3-phenylpropanol (HCOL) as the major product with HCOL selectivity of 67.2%, while PtCo@mSiO2 yields 3-phenylpropionaldehyde with selectivity of 51.8% under the same conditions. The enhanced catalytic performance of Pt-CoxOy@mSiO2 for hydrogenation of CAL to COL is ascribed to the Pt surface electron deficiency induced by metal-oxide interaction, and the protection of active NPs by silica shells results in good catalytic stability.

Grain boundary and interface interaction of metal (copper/indium) oxides to boost efficient electrocatalytic carbon dioxide reduction into syngas

Electrochemical conversion of carbon dioxide (CO2) into syngas is considered a promising approach to mitigate global warming and achieve the recycling of carbon resources. In this work, a series of core–shell metal (copper/indium) oxides with abundant grain boundaries (GBs) between the amorphous In2O3 and cubic Cu2O have been prepared by template-assisted co-precipitation method and tested for the synthesis of syngas by electrochemical CO2 reduction reaction (CO2RR). The phases of Cu2O and In2O3 are independent in bimetallic oxides and do not form any alloy oxidation phase, thus Cu2O and In2O3 can maintain their crystal structure and chemical properties in bimetallic oxides. The Cu2O and In2O3 would been completely reduced to metallic Cu and In during CO2RR. The derived copper/indium possesses the maximum FE of CO (80 %) at −0.77 V vs. reversible hydrogen electrode (RHE) and a good stability of 10 h in an H-type cell. Further applied the copper/indium oxide in the MEA reactor, the FE of CO is more than 80 % at 2.6 V and the total FE of syngas is near 100 % at all applied potentials. More importantly, the H2/CO ratios can be tuned from 1/1 to 1/4 by changing the applied voltages in MEA. Therefore, this study provides a promising strategy to promote the electrocatalytic CO2RR conversion by creating abundant grain boundaries in bimetallic oxides to regulate the ratio of H2/CO.

Unveiling the Degradation of Pt/NbOx/C Catalysts in PEMFCs via In Situ X-ray Absorption Spectroscopy

Among the class of the catalyst that is composed of metal nanoparticles supported on metal oxides (MMO), the Pt/NbOx/C system has shown promising oxygen reduction reaction (ORR) activities as a cathode of proton exchange membrane fuel cells (PEMFCs). Herein, we have studied a series of Pt/NbOx/C catalysts prepared via physical vapor deposition and unraveled the nature of the metal and metal oxide interaction (MMOI) by characterizing this system under reactive conditions. By conducting in situ X-ray absorption spectroscopy (XAS) experiments, we demonstrate that Pt preferably interacts with O but not Nb in the Pt/NbOx/C system. As such, Pt-O interaction benefits the ORR activity via an electronic effect rather than a strain effect. We have also provided clear evidence for the formation of metallic Nb phase at the early stage of PEMFC operation, which led to severe particle growth of Pt after long-term PEMFC operation.

Revealing the effect of metal-support interactions at the Ni/In2O3(111) interface on the selective CO2 hydrogenation

In2O3-supported Ni catalysts exhibit remarkable catalytic activity and selectivity in CO2 hydrogenation to methanol, but the underlying mechanisms and metal-oxide interactions during the reaction remain elusive. Herein, we investigate the Ni-In2O3 interaction by physical vapor deposition of Ni onto well-defined In2O3(111) thin films. In-situ near ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) was employed to probe the CO2 hydrogenation processes on these Ni/In2O3(111) model systems. Our results reveal that the small Ni clusters supported on the In2O3(111) surface at low Ni coverages exhibit cationic states. The chemical bonding and associated electron transfer at the Ni/In2O3(111) interface play crucial roles in the activation of H2 and CO2. Importantly, reaction intermediates (CO3*, OH, and HCOO*) are readily formed and desorbed under CO2 hydrogenation conditions. Our study highlights the significance of metal-support interactions on the selectivity of CO2 hydrogenation. These findings provide valuable insights into the rational design of advanced In2O3-based catalysts for CO2 hydrogenation.

An Insight into Synergistic Metal-Oxide Interaction in CO2 Hydrogenation to Methanol over Cu/ZnO/ZrO2

The metal-oxide interaction is of significance to the construction of active sites for Cu-catalyzed CO2 hydrogenation to methanol. This study examines the effect of ZnO and ZrO2 composition on the Cu/ZnO/ZrO2 catalyst structure and surface properties to further tune the catalytic activity for methanol synthesis. The ZnO/ZrO2 ratio can impact the CuZn alloy formation from strong Cu-ZnO interactions and the surface basic sites for CO2 adsorption at the Cu-ZrO2 interface. The proportional correlation of the CuZn alloy content and CO2 desorption amount with the space-time yield (STY) of methanol reveals a synergistic interaction between Cu and oxides (ZnO and ZrO2) that enhances methanol synthesis. The optimized Cu/ZnO/ZrO2 catalyst exhibits higher STY relative to the traditional Cu/ZnO/Al2O3 catalyst. The obtained results presented herein can provide insight into the catalyst design for methanol synthesis from CO2.

Facile Synthesis of Supported Ir-Based OER Electrocatalysts Via Sputtering

Hydrogen has been regarded as a promising energy carrier for renewable energy systems with net zero emissions [1]. However, the vast majority of industrial hydrogen has been produced from fossil fuels with high carbon dioxide (CO2) emissions [2]. An emerging method for hydrogen production potentially free of greenhouse gas emissions (so-called green hydrogen) is water electrolysis coupled to renewable energy sources such as wind, solar, hydropower, etc [3]. Among several water electrolysis technologies, proton exchange membrane water electrolyzers (PEMWEs) are the most promising due to several inherent advantages [4]. However, the large amount of iridium (Ir) used in current PEMWEs versus the limited amount of Ir resource on earth impedes large-scale and sustainable deployment of PEMWEs [5]. Lowering the amount of Ir used to efficiently catalyze the oxygen evolution reaction (OER) at PEMWE anodes might be achieved through the development of novel electrocatalysts.One strategy to reduce the Ir content of PEMWE anodes is to put Ir onto a support. This strategy can not only reduce the Ir content by improving Ir utilization in comparison with unsupported Ir-based electrocatalysts, but also decrease the Ir packing density [6]. Low Ir packing density is required for electrocatalyst layers with low Ir-contents to be sufficiently thick to ensure robust interfaces between the electrocatalyst layer and the porous transport layer (PTL) and membrane [7]. This strategy has two critical steps: (1) finding/developing a robust support and (2) depositing Ir onto the support with desired morphology with a method that is affordable, scalable, and manufacturable [8].Here we report a one-step deposition of Ir onto nanoscale tungsten-doped titanium dioxide (W-TiO2) powders via sputtering. Characterization shows that Ir is deposited onto the surface of W-TiO2 (Figure 1) in the mixed form of metallic Ir and Ir oxides with particle sizes smaller than 2 nm. The catalyst exhibits an OER mass activity twice that of Ir black in acidic media. Powder conductivity measurements confirm that the electrocatalyst is electrically conductive (~24 S/cm) despite the low conductivity of the W-TiO2 powders (~1×10-4 S/cm). Our study suggests that sputtering is a feasible deposition method for large-scale production of supported Ir-based OER electrocatalysts. Acknowledgement. This study is sponsored by internal funding from Plug Power. The sputter was done at Exothermics Inc., 14 Columbia Dr, Amherst, NH 03031 References [1] Hydrogen for Net-Zero. In A critical cost-competitive energy vector. Edited by. Hydrogen Council, McKinsey & Company; 2021.[2] IEA (2021), Global Hydrogen Review 2021, IEA, Paris (available via the Internet at: https://www.iea.org/reports/global-hydrogen-review-2021)[3] Emonts, B., Müller, M., Hehemann, M., Janßen, H., Keller, R., Stähler, M., ... & Kasselmann, S. (2022). A Holistic Consideration of Megawatt Electrolysis as a Key Component of Sector Coupling. Energies, 15(10), 3656.[4] Zhang, K., Liang, X., Wang, L., Sun, K., Wang, Y., Xie, Z., ... & Zou, X. (2022). Status and perspectives of key materials for PEM electrolyzer. Nano Research Energy, 1(3), e9120032.[5] Mittelsteadt, C. (Invited) Ir Strangelove: Or How I Learned to Stop Worrying and Embrace the PEM. ECS Meeting s MA2022-01, 1335-1335 (2022).[6] Bernt, M., Hartig‐Weiß, A., Tovini, M. F., El‐Sayed, H. A., Schramm, C., Schröter, J., ... & Gasteiger, H. A. (2020). Current challenges in catalyst development for PEM water electrolyzers. Chemie Ingenieur Technik, 92(1-2), 31-39.[7] Bernt, M., Siebel, A., & Gasteiger, H. A. (2018). Analysis of voltage losses in PEM water electrolyzers with low platinum group metal loadings. Journal of The Electrochemical Society, 165(5), F305.[8] Jia, Q., Ghoshal, S., Li, J., Liang, W., Meng, G., Che, H., ... & Mukerjee, S. (2017). Metal and metal oxide interactions and their catalytic consequences for oxygen reduction reaction. Journal of the American Chemical Society, 139(23), 7893-7903. Figure 1

CuO/LaCeOx catalysts with enhanced metal–support interactions for CO2 methanolization

The activity of CO2 methanolization depends on the realization of metal–oxide interactions with different strengths. The CuO/La0.25CeOx catalyst (La content: 25%) demonstrated superior catalytic activity under the reaction conditions of 260 °C, with a methanol space–time yield (STY) of 0.281 gCH3OH·gcat−1h−1 and a methanol selectivity of 83.3%. This study elucidates the correlation of the metal–support interactions in CuO/LaCeOx catalysts and the promotion of catalytic activity, which mainly shows that the introduction of La leads to enhanced conversion of Ce4+ into Ce3+ in the catalyst, facilitates oxygen vacancy generation, and activates the formate reaction pathway of CO2 hydrogenation. Thus, this study has considerable significance for the progress of efficient and new catalysts for CO2 methanolization.

Ion Beam as an External and Dynamic Metal Reservoir to Induce Nanoparticle Exsolution in Oxides

A central theme in solid oxide fuel cells (SOFC) and electrolyzers (SOEC) is to design stable and catalytically active solid/gas interfaces toward desired reactions. A recent advance in this regard is to synthesize nanoparticles decorated electrodes in a process termed “exsolution”. Exsolution generates stable and catalytically active metal nanoparticles via phase precipitation out of a host oxide. Unlike traditional nanoparticle infiltration techniques, the nanoparticle catalysts from exsolution are anchored in the parent oxide. This strong metal-oxide interaction makes the exsolved nanoparticles more resistant against particle agglomeration as compared to the infiltrated ones. In addition, the exsolved particles also open up the possibility of regeneration of catalysts. To date, the concept of exsolution has been successfully applied to a number of applications including SOFC/SOEC, ceramic membrane reactors, chemical looping combustion, and (electro)catalysis.As the exsolution process starts with a solid-solution that contains the to-be-exsolved transition metal ions, this method is often limited by the intrinsic solubility limit of the host oxide. Here, we propose that ion beam irradiation to be a unique tool to promote exsolution as it can introduce defects and dopants into the host oxides and at concentrations higher than thermodynamic limits. Moreover, due to the surface sputtering effect, ion beam irradiation can modulate the surface morphology, creating novel nanostructures.To demonstrate this approach, we chose thin-film perovskite SrTi0.65Fe0.35O3 (STF) and fluorite Ce0.5Zr0.5O2 (CZO) as model systems, both of which are promising materials in SOFC and SOEC. We modulated metal exsolution in both materials with in-situ 10-150 keV Ni irradiation at 800 °C in vacuum. Ni irradiation on STF controllably changed the exsolved particle composition from unitary Fe to bimetallic Fe-Ni. Moreover, it also reduced the particle size down to sub-2 nm, which outperforms other tuning methods thus far in the literature. As a result, the irradiation-modified STF demonstrated superior catalytic activity toward room-temperature oxygen evolution reactions (OER) than the conventional thermally exsolved STF. Regarding CZO, Ni irradiation also decorated the surface with well-dispersed nanoparticles, leading to enhanced high-temperature H2O splitting kinetics. The effective size and composition control over exsolution highlights the utility of metal ion beams in promoting and tailoring exsolved nanocatalysts for a broad range of applications in clean energy and fuel conversion. Figure 1

Promoting Effect of PbO on Ir Nanosurface Toward Ethanol Electrocatalytic Oxidation in Alkaline Media

Abstract Metal-metal (hydr)oxide interfaces can promote the CO2 selectivity of ethanol oxidation reaction (EOR) due to so-called metal–oxide interaction (MOI). Here, we first show that the mixture of Ir and PbO species at the nanoscale can also form “bifunctional effect” sites, where the C–C bond of ethanol can be effectively cut at Ir sites to generate C1 intermediates, and nearby PbO species could provide oxygenated species. The as-prepared Ir-PbO/C catalysts with a mean metallic nanoparticle size of 2.6 ± 0.5 nm can greatly improve the activity, stability, and C1 pathway selectivity of EOR. Specifically, it exhibits superior mass activity of 1150 mA/mgIr in 1 M NaOH solution containing 1 M C2H5OH. Chronoamperometry tests show that the stability of Ir-PbO/C is also significantly improved compared with Ir/C. In situ electrochemical infrared absorption spectral results confirm that the addition of oxophilic PbO species could accelerate the oxidative removal of COad intermediates, thereby greatly improving catalytic performance. This study may give new insights into designing efficient anode catalysts for the direct ethanol fuel cells (DEFCs).

Revealing the construction of Cu[sbnd]O[sbnd]Ce interfacial sites via increased support utilization for enhanced CO2 electroreduction and Li-CO2 batteries

Leveraging designed electronic oxide-metal interactions (EOMI), cerium-supported copper demonstrates remarkable competitiveness in the carbon dioxide reduction reaction (CO2RR). Nevertheless, the limited utilization efficiency of conventional cerium oxide (CeO2) support hampers the EOMI effect. Furthermore, a comprehensive understanding of the influence of distinct crystalline surfaces of CeO2 on the loaded active copper (Cu) species remains elusive. Herein, oxide carriers with diverse crystal facets are acquire for loading to load Cu species through the incorporation of cerium-based metal organic frameworks (MOFs) precursors. Simultaneously, owing to the elevated specific surface area conferred by MOF precursors, Cu/CeO2 hosts ample catalytically active sites for carbon dioxide (CO2) electrocatalytic reactions and as catalytic cathodes for lithium-CO2 (Li-CO2) batteries. Furthermore, the carbon converted from organic ligands in MOFs precursors not only proficiently immobilizes and disperses the active sites, but also enhances the inherent conductive stability of the oxide while augmenting energy utilization efficiency. Leveraging these advantages, the electrocatalyst derived from MOFs achieves a peak CO2-to-methane Faradaic efficiency of 57.9 %, whereas the assembled Li-CO2 batteries exhibit notable activity and durability, boasting a substantial full-discharge capacity of 8907 mAh/g, a discharge voltage of 2.65 V, and an extended cycle life exceeding 1000 h. Mechanistic investigations were conducted using density functional theory (DFT) calculations to thoroughly explore the impact of CeO2 carrier crystal facets, specifically (111), (100), and (110), on the loaded copper species. Notably, (110) was identified as the optimal facet due to its favorable contributions to electronic structure optimization and stability enhancement.

Electronic Interactions on Platinum/(Metal-Oxide)-Based Photocatalysts Boost Selective Photoreduction of CO2 to CH4.

By supporting platinum (Pt) and cadmium sulfide (CdS) nanoparticles on indium oxide (In2 O3 ), we fabricated a CdS/Pt/In2 O3 photocatalyst. Selective photoreduction of carbon dioxide (CO2 ) to methane (CH4 ) was achieved on CdS/Pt/In2 O3 with electronic Pt-In2 O3 interactions, with CH4 selectivity reaching to 100 %, which is higher than that on CdS/Pt/In2 O3 without electronic Pt-In2 O3 interactions (71.7 %). Moreover, the enhancement effect of electronic Pt-(metal-oxide) interactions on selective photoreduction of CO2 to CH4 also occurs by using other common metal oxides, such as photocatalyst supports, including titanium oxide, gallium oxide, zinc oxide, and tungsten oxide. The electronic Pt-(metal-oxide) interactions separate photogenerated electron-hole pairs and convert CO2 into CO2 δ- , which can be easily hydrogenated into CH4 via a CO2 δ- →HCOO*→HCO*→CH*→CH4 path, thus boosting selective photoreduction of CO2 to CH4 . This offers a new way to achieve selective photoreduction of CO2 .