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The presentation reports enhanced Mo catalysts performance prepared with metal promoters. DFT and Raman studies are utilized to interpret the activity of select cations in the MDA reaction. Binding energies of promoters and their preference site location to internal surface of ZSM-5 are discussed in context of improved aromatic yield.
Transformation of biomass and CO 2 into renewable value-added chemicals and fuels has been identified as a promising strategy to fulfill high energy demands, lower greenhouse gas emissions, and exploit under-utilized resources. Cost-effective and performance-efficient catalysts are of great importance to lowering the conversion cost of biomass and CO 2 . Significant progress has been made to advance the catalyst design for these processes, with metal catalysts playing a critical role in many involved catalytic reactions. Traditional nanoparticle-based metal catalysts still require improvement in metal utilization rates, stability, and selectivity tunability. Single-atom catalysts, which have maximum atomic efficiency and a uniform and tunable metal center, as well as an adjustable metal-support interaction, provide potential opportunities to boost catalyst efficiency and thermal stability. Their well-defined and uniform structure also provides advantages to fundamental studies for understanding of the intrinsic reaction mechanism and site requirement in biomass and CO 2 conversion. In this article, we summarize and highlight the recent advances in converting biomass and CO 2 to renewable fuels and chemicals using single-atom catalysts. We discuss the design principles of single-atom catalysts and their potential applications to biomass and CO 2 upgrading as well as the origins of catalytic activity. Moreover, we compare the catalytic efficiency of various catalysts reported thus to provide a fair assessment of these catalysts. Finally, perspectives are given on the interesting fields that may guide future studies.
Brønsted (BAS), Lewis (LAS), and surface Brønsted (SBAS) acid sites have been investigated for polyethylene (PE) upcycling by zeolite catalysts, but there is no clear consensus regarding their catalytic roles, partly due to the complexity of the catalysts used and varying reaction conditions across studies. This work systematically determined how these sites impact PE conversion rates and product distributions by utilizing a suite of microporous MFI catalysts with varying Si/Al ratios, acid site densities, and inherent mesoporosities. PE conversion rates did not trend with total BAS or LAS densities due to a combination of internal mass transfer limitation and the apparent inability of LAS alone to cleave C–C bonds, but a strong, statistically significant correlation was present with respect to SBAS density and mesopore surface area, jointly, owing to accelerated polymer activation on external surfaces to smaller diffusion-limited chains. However, ingress of these SBAS-derived fragments ultimately remained rate limiting, as demonstrated by solid conversion rates that increased with mesopore surface area at similar SBAS density and likewise increased with SBAS density at similar mesopore surface area. In batch PE cracking reactions, light gaseous product selectivities were most sensitive to total BAS, with higher densities generally exhibiting higher selectivity to C 3 and linear C 4 –C 7 products and higher alkane/alkene product ratios, consistent with increased β-scission turnovers. Insights from this work help systematically clarify the roles of BAS, LAS, SBAS, and mesopores in PE cracking reactions and inform the development of tailored zeolite catalysts for efficient polyolefin upcycling.
Maximizing iridium utilization while maintaining high oxygen evolution reaction (OER) performance remains a persistent challenge in acidic water electrolysis. Immobilizing Ir on conductive, acid-stable supports is promising, yet simultaneously achieving sub-nanometer size, high area coverage, and strong electronic coupling is difficult. Here, we report a sequential surface synthesis on titanium nitride (TiN) that yields uniformly distributed sub-nanometer Ir arrays (∼0.7 nm). Our method uses ethylenediaminetetraacetic acid (EDTA) as a temporal scaffold: it chemisorbs to TiN to install dense chelating sites, captures Ir 3+ ions, and confines Ir cluster growth. A subsequent thermal treatment at 500 °C in a reducing atmosphere removes the ligand shell, while preserving ultrasmall particle size and establishing direct Ir–TiN electronic coupling. The optimized catalyst exhibits mixed Ir 0 /Ir x+ coordination with low charge-transfer resistance (R ct = 19.2 Ω), delivering a mass activity of 342 A g Ir −1 at 1.54 V in acidic electrolyte. In situ X-ray absorption spectroscopy reveals irreversible surface oxidation as the primary stability-limiting factor. This stepwise strategy provides a general framework for supported catalysts that maximize precious metal utilization via sub-nanometer dispersion.
Subnanometer catalysts offer high noble metal utilization and superior performance for several reactions. However, understanding their structures and properties on an atomic scale under working conditions is challenging due to the large configurational space. Here, we introduce an efficient multiscale framework to predict their stability exposed to an adsorbate. The framework integrates a comprehensive toolset including density functional theory (DFT) calculations, cluster expansion, machine learning, and structure optimization. The end-to-end machine-learning workflow guides DFT data generation and enables significant computational acceleration. We demonstrate the approach for CO-adsorbed Pdn (n = 1–55) clusters on CeO 2 (111). Simulation results reveal that CO can facilitate restructuring by stabilizing smaller planar structures and bilayer structures of specific intermediate sizes, consistent with experimental reports. Metal–support interactions, preferential CO adsorption, and metal nuclearity and structure control catalyst stability. As a result, the framework allows automatic discovery of stable catalyst structures and a systematic strategy to exploit properties in the subnanometer scale.
Since 2018, the Western Combined Heat and Power Technical Assistance Partnership (CHP TAP) has been dedicated to advancing the adoption and implementation of Combined Heat and Power. The CHP TAP has diligently worked towards its mission of fostering end-user engagement, promoting technical solutions, and enhancing energy security within the region. As we reflect on our journey, we are proud to announce the completion of the required metrics set forth at the beginning of our endeavor. From the outset, our aim has been clear: to leverage CHP technology as a catalyst for bolstering American competitiveness, utilizing local fuels, and fortifying energy resilience. Through collaborative efforts with a diverse array of stakeholders, including manufacturing, commercial, institutional, and federal facilities, and campuses, we have strived to realize this vision. In this report, we outline the achievements, activities, and impact of the Western CHP TAP, highlighting the transformative journey undertaken since 2018. From providing technical assistance and guidance to conducting educational workshops and advocating for supportive policies, our initiatives have been guided by a commitment to excellence and innovation. As we celebrate the completion of our required metrics, we reaffirm our dedication to continuing our mission, building upon our accomplishments, and shaping a sustainable energy future for the Western region. Through ongoing collaboration and engagement, we are confident that the Western CHP TAP will continue to serve as a beacon of progress and a catalyst for positive change in the years to come.
The rise in energy demands and the deleterious environmental issues related to fossil fuels has led to a surge of interest in hydrogen as a "green" alternative. Hydrogen's extraordinary energy density makes it a potential energy and economic "power"-house. Significant research has been dedicated to materials-based hydrogen storage. One area, liquid organic hydrogen carriers (LOHC) is of substantial interest for the reversible transportation of hydrogen from production to end-use facilities. There are challenges associated with this technology including the dependency on precious metal-based catalysts. Recent work in frustrated Lewis pair (FLP) catalysis demonstrates promise for addressing these challenges. Here this review is focused on assessing recent literature on the utilization of intermolecular FLP main group catalysts for improved hydrogenation/dehydrogenation of various substrates including potential LOHC complexes. This review will present an overview of FLPs, highlight potential hydrogen storage applications, and propose areas where knowledge gaps exist that require further investigations.
Hydrothermally stable diesel oxidation catalysts (DOCs) with improved low-temperature activity are desired for the abatement of emissions from diesel vehicles. Herein, novel palladium(Pd)/SiO 2 (core)@Zr(shell) structured DOCs were developed. SiO 2 was completely covered by an 8.4 nm thickness Zr-based shell using a hard template method. The SiO 2 @Zr support was decorated by Pd and evaluated under a simulated diesel exhaust stream. Degreened 1 wt% Pd/SiO 2 @Zr achieved 90% CO and total hydrocarbon conversion at 178 and 372 °C, respectively (feed: 6% CO 2 , 12% O 2 , 6% H 2 O, 400 ppm H 2 , 2000 ppm CO, 100 ppm NO, 1667 ppm C 2 H 4 , 1000 ppm C 3 H 6 , 333 ppm C 3 H 8 ; HCs in C 1 basis and GHSV = 113,000 h –1 ). After hydrothermal aging, only a minor deactivation was observed, while the surface area of 1 wt% Pd/SiO 2 @Zr was as high as 104 m 2 /g. The hydrothermal stability of 1 wt% Pd/SiO 2 @Zr was attributed to the poor crystallinity of SiO 2 @Zr, possibly due to the formation of Si-O-Zr bonds. Lastly, this work highlights the promising potential of utilizing durable Pd/SiO 2 @Zr catalysts for diesel oxidation applications.
Employing the strong metal-support interaction (SMSI) effect for promoting the catalyst's activity toward the oxygen reduction reaction (ORR) is promising due to the electronic structure optimization and high utilization efficiency of platinum group metal (PGM) catalysts. Metal oxides as alternative supports for PGMs facilitate intrinsic activity and improve durability as compared to conventional carbon supports. However, the restricted mass and electron transfer at the metal/support interface need to be addressed. Herein, to strengthen the interaction at the metal/support interfaces and improve the utilization efficiency of PGM, an ultralow loading of Pd was embedded in a surface-oxygenated PdNiMnO porous film. The Mn-doping was designed to promote surface oxygenation using a facile anodization process that created sufficiently exposed interfaces between Pd and the support, strengthening the SMSI effects at the Pd/oxygenated support interface for enhancing ORR performance. Furthermore, the Ni-containing oxygenated catalyst served as both the active component for the oxygen evolution reaction (OER) and the functional support for stabilizing Pd, making PdNiMnO a bifunctional catalyst for zinc–air flow batteries (ZAFB). As a proof-of-concept, the ZAFB (PdNiMnO) shows a maximal power density of 211.6 mW cm –2 and outstanding cycling stability for over 2000 h with a minimal voltage gap of 0.69 V at a current density of 10 mA cm –2 , superior to the state-of-the-art catalysts.
Abstract A significant challenge in designing supported metal‐ligand catalysts for solution‐phase reactions is the stabilization of the metal active sites against leaching into solution. Here, we examine alkene hydrosilylation reactions as model systems to improve the stability of highly dispersed Pt using a metal‐ligand coordination strategy on high surface area oxide supports. By evaluating a series of bidentate N‐based ligands, we demonstrate several design strategies to improve stability of the highly dispersed Pt 2+ centers against leaching, while maintaining a high level of catalytic activity, selectivity, and recyclability for alkene hydrosilylation batch reactions under mild conditions. These involve a bi‐functional approach to ligand design, which considers interaction to the support and a well‐defined coordination environment for the metal active site. Three strategies are reported: modifying ligands for stronger interaction with oxide surfaces, mixing ligands, and pre‐depositing an “anchoring ligand” to the support before loading the metal‐ligand catalyst. Each of these is successful in enhancing Pt recyclability. Particularly, two Pt‐phenanthroline catalysts exhibit excellent reusability for multiple batch reaction cycles, due to high stability of the active Pt species. Addressing the active site leaching problem significantly enhances the utility of ligand‐coordinated supported metal catalysts as highly stable and selective catalysts for solution‐phase reactions.
Abstract Early‐stage cost evaluation during catalyst development holds the potential to accelerate the commercialization and deployment of advanced catalytic materials for sustainable chemical processes. The modeling and assessment of manufacturing costs as early as the laboratory synthesis scale, for example, focusing on materials costs and synthesis performance metrics, can support the development of an experimental–economic feedback loop that enables rapid insight into cost drivers associated with catalyst synthesis and highlights areas that require focused research and development effort. Ultimately, this feedback loop supports the realization of an economic understanding of the overall synthetic process and highlights opportunities to reduce costs, serving as the foundation for the scale‐up of catalyst manufacturing. Herein, a case study is presented utilizing CatCost, a free and publicly available estimation tool for the evaluation of catalyst manufacturing costs, to perform a cost‐responsive optimization of the synthesis of nickel nanoparticles (Ni NPs). It is demonstrated that reagent substitutions with more cost‐effective analogs, coupled with stoichiometric optimization, afford a 58% reduction in raw materials cost without changing the product yield or properties.
Abstract CO 2 reduction is a highly attractive route to transform CO 2 into useful feedstocks, of which C 2 products are more desired than C 1 , yet face high kinetic barriers of C−C electrocoupling. Here, the engineering of pore‐enabled local confinement reaction environments is reported for tuning the enrichment of surface‐adsorbed oxygen‐relevant species and the establishment of their pronounced benefits in promoting C−C coupling over oxide‐derived Cu‐based catalysts. A new approach of utilizing the microphase separation of a block copolymer is developed to fabricate bicontinuous mesoporous CuO nanofibers (CuO‐BPNF). The enhanced confinement from long‐range mesochannels enables the adsorption of OH ad /O ad on the Cu surface at a wide negative potential range of −0.7 – −1.3 V in CO 2 reduction, which cannot be achieved over conventional deficient and short‐range pores. Constant‐potential DFT calculations reveal that the surface‐bound oxygen species weakens *CO affinity with the Cu (111) surface and lowers the kinetic barriers for both *CO−CO dimerization and *CO hydrogenation to enable *CO−CHO coupling. Accordingly, a CO 2 ‐to‐C 2 Faradaic efficiency of 74.7% over CuO‐BPNF is shown, significantly larger than counterparts with conventional pores. This work offers a general design principle of confinement engineering to manage the adsorption of reactive species for steering reaction pathways in interfacial catalysis.
Sunlight-powered artificial leaves for the production of formate from CO 2 are an attractive route to solar fuels, yet existing solar formate devices remain low in performance, and their architecture and material choices are underexplored. Herein, we report the fabrication of two distinct fully integrated, self-standing solar formate device architectures and elucidate the underlying design principles and material selection strategies. The first architecture integrates a Si photocathode with a BiVO 4 photoanode and utilizes a highly active Pd catalyst for CO 2 reduction. It represents the first artificial leaf device comprising two photoelectrodes (excluding photovoltaic [PV]-biased electrodes) for effective formate production under single-beam illumination. The second architecture employs a dark cathode and a dark anode driven by a 4-junction perovskite solar cell and uses a highly stable Bi catalyst for CO 2 reduction. This device delivers a record-high formate production rate of 174 µmol h −1 with a remarkable solar-to-formate energy efficiency of 2% among all artificial leaf devices reported to date. Finally, these results demonstrate the feasibility and outline the design principles of both PV-free and PV-assisted device architectures in solar fuel production.
The Intensified Biogas to Liquid (IBGTL) process aims to overcome traditional economy-of-scale barriers in biogas-to-liquid fuel production by integrating bi-reforming and Fischer-Tropsch synthesis (FTS) in a single IBGTL reactor. This reactor operates at uniform pressure with different optimized temperatures across two zones for efficient conversion, utilizing multifunctional bi-reforming catalysts and high-temperature FTS catalysts. Bench scale experiments were carried out using landfill gas (LFG) in a single pass process, and the yield data from these experiments were fed into process scale-up design and techno-economic analysis (TEA) across four scenarios: (1) a single pass process, (2) a process with material recycling, (3) a process with liquefied petroleum gas (LPG) co-product recovery, and (4) a process with electricity generation from the fuel gas produced. TEA identified Scenario 2 as the most cost-effective, achieving a Minimum Fuel Selling Price (MFSP) of $\$4.59$ per gallon, competitive with the current national diesel price of $\$4.7$ per gallon. However, comparison with the conventional two-reactor system highlights the need for catalyst performance improvements. Sensitivity analysis emphasized the importance of manufacturing cost, liquid fuel yield, and biogas flow rate. Further analysis determined that the IBGTL process must achieve a diesel mass yield beyond 11.7% to surpass the economic viability of the conventional TriFTS (Tri-reforming followed by Fischer-Tropsch Synthesis) process. If the IBGTL process attains the TriFTS yield of up to 17%, the resulting MFSP could be approximately 31% lower than the current TriFTS MFSP. Furthermore, renewable energy credits and carbon credits can further enhance the economic viability of BGTL processes.
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Alkaline anion-conducting polymer-based CO 2 electrolysis and water electrolysis are among two emerging renewable energy conversion technologies. Their system design and integration offer promise of lower capital cost due to utilization of low-cost catalysts, in contrast to platinum group metal catalysts required for cation-conducting polymer-based devices. However, a critical component, the polymer electrolyte membrane, remains an obstacle hampering system performance and durability. In this study, commercially-available Sustainion® membranes with and without PTFE-reinforcement were investigated to understand previously unreported origins of improved device performance when compared to alternative membrane chemistries. We report critical membrane properties, such as morphology, thermal stability, as well as temperature-, hydration-, and counter-ion dependent ion conductivity. Moveover, the changes in uptake and conductivity of membranes in supporting electrolytes of K 2 CO 3 and KOH investigated as a function of their concentration. Presence of reinforcement and supporting electrolyte type alter the membrane's transport functionality, which could help guide device design for improved performance. In conclusion, the obtained results not only show how Sustainion® properties change with operating environment for CO 2 and water electrolysis applications, but also provide understanding for internal and external factors controlling anion-exhcnage membrane functionality in electrochemical devices.
Proton-exchange-membrane water electrolysis (PEMWE) requires acidic oxygen-evolution-reaction (OER) anodes that combine high activity, high durability, and low Ir loading. Here, we report a Ti-Zr composite electrospun oxide (ESO) nanorod support that enables ultralow-Ir anodes for high-performance PEMWE. Zr-containing Ti oxide heterostructures stabilize anatase-rich TiO2, tune the local oxygen-coordination environment, and strengthen interfacial anchoring of IrOx under acidic anodic conditions. The electrospun nanorod network further creates an open, mechanically coherent catalyst layer that improves Ir utilization, ionomer penetration, and mass transport. At an anode loading of 0.2 mgIr cm-2, the optimized Ir/TiZr20-ESO anode delivers a PEMWE mass activity of 0.99 A mgIr-1 at 1.45 V, 28.3 and 43.0 times higher than commercial Ir black and commercial IrO2/TiO2, respectively. The same anode reaches 3.0 and 4.0 A cm-2 at 1.75 and 1.83 V, respectively, and sustains 2000 h operation at 2.0 A cm-2. Also, accelerated stress tests up to 525 hours over 31,500 cycles confirm promising long-term durability, with an insignificant performance decay of 0.4 μV per cycle. Density functional theory indicates that the Ti-Zr oxide heterostructure suppresses Ti demetallation and strengthens IrO2 interfacial binding, rationalizing the improved high-current-density stability.
State-of-the-art OER (oxygen evolution reaction) catalyst syntheses require the use of expensive metals (i.e. Ir) with complex and time-consuming synthetic routes, difficulty in control, and impractical yields. Although some reported catalysts show improved performance (i.e. activity, stability, lowering Ir content with Ru), their synthesis is costly and not viable for scale-up. Here we demonstrate a practical, reliable, and scalable one-pot synthesis method for OER catalysts based on borohydride reduction to quickly yield >100 mg of Ir, Ru, and IrRu nanoparticles (1.6 ± 0.2 nm) with outstanding batch-to-batch consistency. Both mono- and bi-metallic compositions exhibit a metal-core/metal-oxide-shell nanoparticle structure. We further demonstrate the versatility of this method by incorporating earth-abundant yttrium, resulting in a catalyst with improved precious metal utilization for OER. This method serves as a robust platform for generating ultrasmall (<2 nm) multi-metal particles useful for electrocatalysis research.