Catalyst Pretreatment Research Articles

Unraveling the role of reducing atmospheres on Fe-Zn-Al catalysts for highly selective carbon dioxide hydrogenation to light olefins

This study investigates the carbon dioxide (CO2) hydrogenation performance of Fe-Zn-Al catalysts pretreated under four distinct reducing atmospheres (H2, H2/N2, H2/CO, and CO/N2), elucidating their impact on CO2 conversion, CO selectivity, and light olefins selectivity. Combined with the characterization results, it was found that various catalyst components were obtained after activation in different atmospheres, but Fe5C2 was observed in all the catalysts after the CO2 hydrogenation reaction. The catalytic performance is intricately linked to the type of surface species produced after reduction and the Fe5C2 content. In a comparative perspective, the catalytic activity of the same catalyst in the four atmospheres followed the sequence H2>H2/N2>CO/N2>H2/CO. Notably, catalyst pretreatment with H2 yielded the highest CO2 conversion rate at 31.6 % and light olefins selectivity at 40.2 %. These results can be attributed to the highest electron density detected by XPS for the iron species on the spent catalyst and to the largest concentration of Fe5C2 formed during the reaction in the hydrogen reduced sample.

Disintegration of lignocellulosic material through visible light SiO2/g-C3N4 photocatalyst for biogas generation

This study presents the synthesis of g-C3N4 and the fabrication of SiO2/g-C3N4 via the hydrothermal polycondensation method, serving as a highly efficient visible light activated photocatalyst for enhancing anaerobic digestion and biogas production from rice straw through pretreatment at various time intervals. The efficacy of the pretreatment was evaluated using a range of analytical techniques, including XRD, FTIR, FESEM, EDX, and UV–vis analysis. The results showcased a remarkable 81 % reduction in silica content compared to untreated rice straw, along with a significant 121 % increase in biogas production. The study demonstrate that the 7-h treatment duration facilitates the highest silica reduction and biogas yield. These findings underscore the immense potential of SiO2/g-C3N4 as a promising catalyst for rice straw pretreatment, thereby leading to enhanced biogas production during anaerobic digestion.

The effect of hydrothermal pretreatment on the catalytic performance of Zn/HZSM-5 catalysts for ethylene aromatization reaction

To address the issue of coking and deactivation of Zn/HZSM-5 catalysts used for lightolefins aromatization, a high-temperature hydrothermalmethod was employed for catalyst pretreatment. The catalysts were characterized using XRD, N2 physical adsorption-desorption, NH3-TPD, Py-FTIR, XPS, and TG techniques. The effect of high-temperaturehydrothermal pretreatment on the catalytic performance and stability of the catalyst was investigated using ethylene aromatization as a probe reaction. The results showed that the Zn/HZSM-5 catalyst exhibited excellent catalytic performance after48 h of high-temperature hydrothermal pretreatment. Although the conversion of ethylene slightly decreased, the catalyst lifetime was significantly extended, increasing from 72to 216 h, while the aromatics selectivity remained above 60%. It was suggested that the hydrothermal treatment enhanced the interaction between ZnO species and Brønsted acid sites, promoting the generation of ZnOH+ species. This not only suppressed the hydrogen transfer reaction but also significantly enhanced the dehydrogenation performance of the catalyst, improving the selectivity towards hydrogen. Additionally, the catalyst exhibited increased carbon capacity and reduced carbon deposition rate after hydrothermal treatment, demonstrating excellent anti-coking properties.

Investigation of sawdust microwave-assisted pyrolysis by machine learning, Part I: Optimization insights by large language models

Microwave-assisted catalytic pyrolysis shows promise for efficiently converting waste biomass, such as sawdust, into valuable bio-oil. However, current research on pyrolysis characteristics predominantly relies on conventional trial-and-error experimentation. This work pioneers the first use of large language models (LLMs) to gain insights into optimizing bio-oil yield by analyzing the effects of catalyst loading and pretreatment temperature on product distribution. Additionally, we encode the textual LLM outputs into distributed vectors via Word2Vec and concatenate them with artificial neural network (ANN) embeddings, capitalizing on the complementary strengths of data-driven and language models. Our results demonstrate superior accuracy and interpretability, providing better optimization insights on heating dynamics and energy efficiency while avoiding extensive experimental costs. This research establishes the prospects of LLMs as supplementary tools for thermochemical conversion studies, potentially reducing resource-intensive lab trials through reliable data-driven predictions.

Highly Efficient PtSn/Al2O3 and PtSnZnCa/Al2O3 Catalysts for Ethane Dehydrogenation: Influence of Catalyst Pretreatment Atmosphere

Increased demand for ethylene has motivated direct ethane dehydrogenation over Pt-based catalysts. PtSn/γ-Al2O3 and PtSnZnCa/γ-Al2O3 catalysts were investigated with the aim of understanding the effect of the pretreatment environment on the state of dispersed Pt for ethane dehydrogenation. The catalysts were prepared by the impregnation method and pretreated in different environments like static air (SA), flowing air (FA), and nitrogen (N2) atmospheres. A comprehensive characterization of the catalysts was performed using Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), Temperature-Programmed Reduction (TPR), NH3 Temperature-Programmed Desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM) techniques. The results reveal that the PtSn on Al2O3 catalyst pretreated in the static air environment (PtSn-SA) exhibits 21% ethylene yield with 95% selectivity at 625 °C. XPS analysis found more platinum and tin on the catalyst surface after static air treatment. The overall acidity of the catalysts decreased after thermal treatment in static air. Elemental mapping demonstrated that Pt agglomeration was pronounced in catalysts calcined under flowing air and nitrogen. These factors are responsible for the enhanced activity of the PtSn-SA catalyst compared to the other catalysts. The addition of Zn and Ca to the PtSn catalysts increases the yield of the catalyst calcined in static air (PtSnZnCa-SA). The PtSnZnCa-SA catalyst showed the highest ethylene yield of 27% with 99% selectivity and highly stable activity at 625 °C for 10 h.

Best practices in the characterization of bulk catalyst properties

Bulk characterization of a solid provides us with a spatially-averaged description of its physical and chemical properties. These properties are not site-specific, but they are critical for categorizing materials and understanding their catalytic performance. Important bulk chemical properties include elemental composition, crystal structure, atomic coordination environment, and the oxidation states of elements comprising the catalyst. Significant physical properties include accessible surface area, pore volume, pore diameter, and particle size distributions that exist at the various length scales of catalysis. Each physicochemical property is sensitive to the conditions employed for catalyst synthesis, storage, pre-treatment, activation, and characterization. Thus, it is imperative that authors fully describe materials and methods in publications as this metadata provides context for observed phenomena and allows others to recreate the exact conditions that are essential for reproducibility. Such protocols are necessary for a meaningful interpretation of differences in catalyst performance observed across laboratories. This perspective article defines bulk characterization, provides guidance on bulk characterization methods, and emphasizes important considerations and best practices. Our aim is to build a more nuanced understanding of catalyst characterization. We hope that awareness and application of the principles outlined herein will improve rigor and reproducibility in catalysis science.

Thermal degradation of emerging pollutants in municipal solid wastes and agro wastes: effectiveness of catalysts and pretreatment for the conversion of value added products

In this study, emerging soil pollutants in the form of municipal solid waste (MSW) and agricultural waste were converted into biofuel via thermal degradation process. Among various waste-to-energy conversion processes, the pyrolysis of biomass is considered the most significant due to its maximum biofuel yield than other conversion techniques. Individual and co-pyrolysis of MSW and sugarcane residue (SR) as well as its treated variant (TSR) were performed in a lab-setup fixed-bed reactor with and without catalyst. The effect of acid pretreatment and catalytic effects on the pyrolysis process was assessed in terms of product yields and characterization. The acidic pretreatment of SR and catalyst in the pyrolysis process alters the process yield and its composition. The maximum oil yield of 50.5 wt% was achieved by catalytic co-pyrolysis of MSW + TSR + HZSM5, whereas the maximum gas yield of 38.1 wt% was achieved by catalytic co-pyrolysis of MSW + SR + HZSM5. This suggests that intrinsic minerals present in the biomass and MSW, particularly alkali and alkaline earth metals, have a catalytic effect on the devolatilization of organic material and the char cracking event. The pretreatment of biomass showed considerable improvement in the properties of the produced pyrolysis oil and char. Compared to the pyrolysis oil and char obtained from MSW + SR, the oil and char obtained from MSW + TSR + HZSM5 showed a small increment in their heating values. Pretreatment and the catalytic co-pyrolysis process influenced the structure of the pyrolysis oils, increasing the production of phenolic compounds and aromatic hydrocarbons. The amount of gas components in pyrolysis gas, such as CH4, CO2, and CO also changed more according to the feedstock used for the process. Overall, the HZSM-5 catalyst and co-pyrolysis of MSW with pretreated SR enhanced the pyrolysis conversion of waste municipal solids and agricultural wastes into energy-rich products.

Dynamic Copper Site Redispersion through Atom Trapping in Zeolite Defects.

Single-site copper-based catalysts have shown remarkable activity and selectivity for a variety of reactions. However, deactivation by sintering in high-temperature reducing environments remains a challenge and often limits their use due to irreversible structural changes to the catalyst. Here, we report zeolite-based copper catalysts in which copper oxide agglomerates formed after reaction can be repeatedly redispersed back to single sites using an oxidative treatment in air at 550 °C. Under different environments, single-site copper in Cu-Zn-Y/deAlBeta undergoes dynamic changes in structure and oxidation state that can be tuned to promote the formation of key active sites while minimizing deactivation through Cu sintering. For example, single-site Cu2+ reduces to Cu1+ after catalyst pretreatment (270 °C, 101 kPa H2) and further to Cu0 nanoparticles under reaction conditions (270-350 °C, 7 kPa EtOH, 94 kPa H2) or accelerated aging (400-450 °C, 101 kPa H2). After regeneration at 550 °C in air, agglomerated CuO was dispersed back to single sites in the presence and absence of Zn and Y, which was verified by imaging, in situ spectroscopy, and catalytic rate measurements. Ab initio molecular dynamics simulations show that solvation of CuO monomers by water facilitates their transport through the zeolite pore, and condensation of the CuO monomer with a fully protonated silanol nest entraps copper and reforms the single-site structure. The capability of silanol nests to trap and stabilize copper single sites under oxidizing conditions could extend the use of single-site copper catalysts to a wider variety of reactions and allows for a simple regeneration strategy for copper single-site catalysts.

Effect of surface modification of Fe/g-C3N4 catalyst on the product distribution in CO hydrogenation

Carbon nitride (g-C3N4) prepared using thermal condensation of urea was pretreated by H2O2/NH3·H2O and used as support to obtain Fe/g-C3N4 catalyst via impregnation method. The catalytic performance of the catalysts both before and after modification was investigated in CO hydrogenation. Combining detailed characterizations, such as XRD, SEM, TEM, FT-IR, TG, CO2-TPD, CO-TPD, H2-TPR, contact angle measurement, and N2 physical adsorption and desorption, we investigated the effects of surface pretreatment on the texture properties of Fe/g-C3N4 catalysts and the product distribution of CO hydrogenation. The results demonstrate that various pretreatment techniques have significant influences on the textural properties and catalytic performance of the catalysts. The prepared g-C3N4 with a typical honeycomb structure has strong interaction with highly dispersed Fe. Both before and after modification, the materials are hydrophilic, and the hydrophilicity is increased after treatment with H2O2 and NH3·H2O. Treatment with H2O2 enhances surface hydroxyl groups. NH3·H2O treatment improves surface amino groups, promotes CO adsorption, and facilitates the formation of Fe(NCN) phase. The surface basicity of all pretreated catalysts is enhanced. The water gas shift (WGS) reaction activity of the two-step modified catalyst Fe/AM-g-C3N4 was lower, and the CO2 selectivity in CO hydrogenation was reduced to 11.61%. Due to the enhanced basicity of Fe/AM-g-C3N4, the secondary hydrogenation ability of olefins was inhibited to obtain higher olefin selectivity with C= 2–C= 4 of 32.37% and an O/P value of 3.23.

Uncalcined TS-1 supported Au catalyst via NaBH4 reduction method for propylene epoxidation: Insights into the H2 pretreatment effect on catalytic performance

Stable and efficient Au-supported titanium silicalite-1 (TS-1) catalysts are essential for the direct epoxidation of propylene (DEP) using O2 and H2. But the deposition-precipitation method for Au/TS-1 contains low Au capture efficiency and rapid deactivation rate. Herein, Au/TS-1-B (uncalcined TS-1) catalysts were synthesized through a NaBH4 reduction method. The impact of H2-thermal-pretreatment on DEP activities was studied. H2-pretreatment can enhance propylene oxide selectivity, shorten activation time and reduce deactivation rate of catalyst. Organic-templates on the surface of TS-1-B and stabilizers coated on Au-nanoparticles can be partially removed under H2-treatment, thus exposing more active sites for Au and Ti and facilitating their interactions. Furthermore, more porous structures with reduced acid sites and enhanced surface hydrophobicity of pretreated catalyst can promote DEP reaction. Solid stability in TS-1-B, high Au utilization resulting from the reduction method, and favorable modifications through H2-thermal treatment contribute to the exploration of more robust DEP catalyst performance.

Promoting Pd-Catalyzed Conversion of CO to Formate

Electrochemical CO2 reduction offers exciting opportunities in turning the waste carbon into value-added chemicals/fuels. Among different CO2 reduction products, formate has attracted particular interest, as it shows promising near-term economic feasibility. Pd-based electrocatalysts have demonstrated excellent selectivity towards formate production, however, only within a narrow potential window of 0 V to -0.25 V vs. RHE. It has shown that Pd-based electrocatalysts suffer from the potential-dependent deactivation pathways (α-PdH to -PdH phase transition, CO poisoning, etc.) and quickly loss their activity towards formate production. Thus, it is desirable to establish new strategies to enable Pd-based CO2 reduction over a broader potential window to achieve both energy efficient and practical relevant formate production.In this work, we discovered that ligands, i.e., polyvinylpyrrolidone, decorated Pd surface exhibits an unexpected promotion effect on CO2 electroreduction. Specifically, these decorated Pd can afford selective formate production at a much-extended potential window (beyond -0.7 V vs. RHE) with significantly improved activity (14-times enhancement at -0.4 V vs. RHE) compared to that of the pristine Pd surface. Combined results from physical/electrochemical characterizations, kinetic analysis and first principal simulations suggest that the capping ligand can effectively stabilize the Pd species with high valence state (Pdẟ+) resulted from the catalyst synthesis and pretreatments. These Pdẟ+ species are responsible for the inhibited phase transition of α-PdH to β-PdH, as well as the suppression of CO and H2 formation. Overall, our study confers a desired catalyst design principle: introducing positive charges into Pd-catalysts to enable efficient and stable CO2 to formate conversion.

Cordierite-Supported Transition-Metal-Oxide-Based Catalysts for Ozone Decomposition

Cordierite-based supported noble-metal-free catalysts for ozone decomposition are elaborated. The cordierite ceramic surface is pretreated with oxalic acid and NaOH, and Mn-Cu-Ni oxide catalysts are prepared by the impregnation method. The mass ratio of the supported oxides in the resulting catalysts is MnO2:CuO:NiO = 3:2:1, and their loadings are from 1.8 to 7.0 wt.%. The pretreated supports and catalysts are characterized by low-temperature N2 adsorption, scanning electron microscopy (SEM), powder X-ray diffraction analysis (XRD), and temperature-programmed reduction with H2 (TPR-H2). The catalysts are tested in ozone decomposition with high airflow rates (20 and 50 L/min) and with initial ozone concentrations of 1 and 2 ppm at temperatures in the range of 25–120 °C. It is shown that a combined treatment of cordierite with oxalic acid and NaOH leads to a developed porous structure and stabilization of supported Mn-Cu-Ni oxides in a highly dispersed state. The high activity of catalysts in ozone decomposition at room temperature and high airflow is demonstrated. The developed catalysts can be recommended for application in purification of air from the ozone because of their high catalytic activity, high mechanical stability, and relatively low weight and cost.

The Effect of Rh/BAC Catalyst Preparation and Pretreatment Methods on Benzene Hydrogenation

The challenge of developing catalytic materials with improved performance relies on the support of metal particles on carbon surfaces. The results of benzene hydrogenation on Rh/BAC (birch activated carbon) prepared by different methods, including adsorption and impregnation, depending on the moisture capacity of the support, were presented. The volumes and diameters of the pores on the BAС surface were determined by BET method, SEM and chemical compositions were characterized. Benzene hydrogenation took place on various carbon-supported catalysts at a temperature of 60 °C and a hydrogen partial pressure of 40.0 MPa. Catalysts produced through the impregnation process were more effective than those produced via adsorption. Rhodium cations enter the micro pores and remain in their metallic form during the adsorption of chloride salt solutions. Hydrogen adsorption on them is facile, while access of benzene molecules is difficult. Prior reduction in the hydrogen flow is essential for full completion of the hydrogenation reaction on catalysts, as rhodium reduction and hydrogenation reaction occur simultaneously.

Phosphorus-Containing Catalyst Impact on Furfural and Glucose Production during Consecutive Hydrothermal Pretreatment and Enzymatic Hydrolysis

Lignocellulosic biomasses have a very important role as raw materials to produce biobased chemicals. However, a sustainable, efficient, and economically competitive way to convert lignocellulosic biomass into these chemicals has still not been achieved. This study is related to the selective separation and conversion of birch wood C5 carbohydrates into furfural during the H3PO4–NaH2PO4-catalyzed hydrothermal pretreatment simultaneously preserving cellulose in the lignocellulosic leftover for glucose production by the enzymatic hydrolysis. The ratio of H3PO4–NaH2PO4 in the catalyst solution was changed (3:0, 2:1, 1:1, and 1:2). Results show that around 64.1 to 75.9% of available C5 carbohydrates were converted into furfural. The results of birch wood lignocellulosic leftover chemical composition analysis show that cellulose losses during the pretreatment stage did not reach more than 10% of the initial amount. Based on the enzymatic hydrolysis screening experiments, a suitable catalyst for pretreatment was selected and an in-depth study was carried out. Enzymatic hydrolysis experiments were organized based on the three-factor central composite face-centered design. The variable parameters were treatment time (24–72 h), enzyme load (10–20 U/g cellulose), and substrate amount in reaction media (10–20%). At optimal conditions, 49.9 ± 0.5% of available cellulose in lignocellulosic leftover was converted into glucose.

Unravelling the Structure Change and Its Catalytic Consequence of CuO Nanowires Towards CO2 Reduction Reaction

The CO2 reduction reaction (CO2RR) is a complex process with many possible products, and maintaining high selectivity for multi-carbon products remains a challenge. Currently, Cu-based catalysts are the only transition metal catalysts that can produce C2 products, and one of the popular Cu-based catalysts is CuO nanowires (NWs). We studied a series of CuO nanowires ranging from 50 to 200 nm for CO2RR using multiple characterization techniques including transmission electron microscopy(TEM), small angle X-ray scattering (SAXS) and in situ X-ray adsorption spectroscopy. We found that there could be an activation process required for such CuO NWs to serve as efficient CO2RR catalysts. The CuO can go through multiple steps resulting in the severe morphology changes during the activation process, confirmed by TEM and SAXS. In situ XAS results showed that the CuO NWs will be reduced from Cu(II) to Cu(0) during the reaction, consistent with our previous work(1). H-cell testing results also indicated the C2 production can be boosted after specific activation pathway, which highlights the importance of catalyst pre-treatment. These findings not only deepen our understanding of CO2RR mechanism but also provide fundamental insights for CO2RR catalysts synthesis. References (1) Soo Hong Lee, Ian Sullivan, David M. Larson, Guiji Liu, Francesca M. Toma, Chengxiang Xiang, and Walter S. Drisdell. ACS Catalysis, 2020, 10(14), 8000-8011 Acknowledgement The authors acknowledge the funding support from the Laboratory Directed Research and Development Program of the Lawrence Berkeley National Laboratory under the U.S. Department of Energy Contract (No. DE-AC02-05CH11231).

Oxygen Plasma Induced Nanochannels for Creating Bimetallic Hollow Nanocrystals.

Platinum-based metal catalysts are considered excellent converters in various catalytic reactions, particularly in fuel cell applications. The atomic structure at the nanocrystal surface and the metal interface both influence the catalytic performance, controlling the efficiency of the electrochemical reactions. Here we report the synthesis of Ag/Pt and Ag/Pd core/shell nanocrystals and insight into the formation mechanism of these bimetallic core/shell nanocrystals when undergoing oxygen plasma treatment. We carefully designed the oxidation treatment that determines the structural and compositional evolution. The accelerated oxidation-triggered diffusion of Ag toward the outer metal shell leads to the Kirkendall effect. After prolonged oxygen plasma treatment, most core/shell nanocrystals evolve into hollow spheres. At the same time, a minor fraction of the metal remains unchanged with a well-protected Ag core and a monocrystalline Pt or Pd shell. We hypothesize that the O2 plasma disturbs the Pt or Pd shell surface and introduces active O species that react with the diffused Ag from the inside out. Based on EDX elemental mapping, combined with several electron microscopic techniques, we deduced the formation mechanism of the hollow structures to be as follows: (I) the oxidation of Ag within the Pt or Pd lattice causes a disrupted crystal lattice of Pt or Pd; (II) nanochannels arise at the defect locations on the Pt or Pd shell; (III) the remaining Ag atoms pass through these nanochannels and leave a hollow crystal behind. Our findings deepen the understanding of interface dynamics of bimetallic nanostructured catalysts under an oxidative environment and unveil an alternative approach for catalyst pretreatment.

Methane Catalytic Combustion under Lean Conditions over Pristine and Ir-Loaded La1-xSrxMnO3 Perovskites: Efficiency, Hysteresis, and Time-on-Stream and Thermal Aging Stabilities.

The increasing use of natural gas as an efficient, reliable, affordable, and cleaner energy source, compared with other fossil fuels, has brought the catalytic CH4 complete oxidation reaction into the spotlight as a simple and economic way to control the amount of unconverted methane escaping into the atmosphere. CH4 emissions are a major contributor to the 'greenhouse effect', and therefore, they need to be effectively reduced. Catalytic CH4 oxidation is a promising method that can be used for this purpose. Detailed studies of the activity, oxidative thermal aging, and the time-on-stream (TOS) stability of pristine La1-xSrxMnO3 perovskites (LSXM; X = % substitution of La with Sr = 0, 30, 50 and 70%) and iridium-loaded Ir/La1-xSrxMnO3 (Ir/LSXM) perovskite catalysts were conducted in a temperature range of 400-970 °C to achieve complete methane oxidation under excess oxygen (lean) conditions. The effect of X on the properties of the perovskites, and thus, their catalytic performance during heating/cooling cycles, was studied using samples that were subjected to various pretreatment conditions in order to gain an in-depth understanding of the structure-activity/stability correlations. Large (up to ca. 300 °C in terms of T50) inverted volcano-type differences in catalytic activity were found as a function of X, with the most active catalysts being those where X = 0%, and the least active were those where X = 50%. Inverse hysteresis phenomena (steady-state rate multiplicities) were revealed in heating/cooling cycles under reaction conditions, the occurrence of which was found to depend strongly on the employed catalyst pre-treatment (pre-reduction or pre-oxidation), while their shape and the loop amplitude were found to depend on X and the presence of Ir. All findings were consistently interpreted, which involved a two-term mechanistic model that utilized the synergy of Eley-Rideal and Mars-van Krevelen kinetics.

Tailoring chemoselectivity of Fe/Ni catalyst for hydrogenation of carbonyl compound

Selective hydrogenation of carbonyl moiety in the presence of olefinic group and other reducible functionality is an industrially important transformation. However, the protocol of green chemistry cannot be sacrificed for its formidable challenging transformation. Therefore, iron nickel bimetallic recyclable catalyst (Fe/Ni) was used for base free hydrogenation of carbonyl compound with high activity and chemoselectivity in microwave environment. The microwave irradiation and pre-treatment of bimetallic catalyst (Fe/Ni) divert conversion/selectivity towards CO group as compared to CC or another reducible moiety. This is further confirmed by DFT calculations which shows that the CO site is strongly interacted with the surface compared to the CC site. The pyridine adsorption studies revealed that pre-treated (Fe/Ni) possess more acidic sites as compared to untreated catalyst. Furthermore, the selectivity of bimetallic catalysts towards hydrogenation of carbonyl function group was correlated with Fe content present in the matrix of catalyst.

Chicken litter-derived catalyst for persulfate activation to remove acetaminophen: An organic-waste-to-wealth strategy

Extracting value from organic waste (e.g., chicken litter) to deliver high-end products should become an essential disposal strategy in the future. Herein, chicken litter was employed as the feedstock to produce a catalyst for peroxydisulfate (persulfate) activation for potential wastewater treatment applications. Three different chicken litter samples were prepared to investigate the effects of inorganic species contained in chicken litter on the catalyst performance: (1) chicken litter without pretreatment, (2) chicken litter washed with 0.05 M HCl, and (3) chicken litter washed with 0.25 M HCl. When the chicken litter-derived catalyst was used for persulfate activation, acetaminophen (ACP) was effectively removed, suggesting a synergic effect. When utilizing the catalyst derived from chicken litter without undergoing HCl pretreatment, the degradation efficiency of ACP reached 84.1%, surpassing that of the pretreated catalysts. The ACP degradation efficiency further improved to 93.8% and 93.9% with increased catalyst dose and persulfate concentration. The reactive oxygen species present during the ACP degradation were analyzed using chemical scavengers. O2•− radicals showed a dominant effect on ACP degradation. ACP degradation was greatly suppressed when HCO3− and humic acid coexisted. Furthermore, combustible byproducts of the catalyst production process can be potentially used to supply energy to the process, which would help lower the overall energy requirement.

Promote electroreduction of CO2 via catalyst valence state manipulation by surface-capping ligand

Electrochemical CO2 reduction provides a potential means for synthesizing value-added chemicals over the near equilibrium potential regime, i.e., formate production on Pd-based catalysts. However, the activity of Pd catalysts has been largely plagued by the potential-depended deactivation pathways (e.g., [Formula: see text]-PdH to [Formula: see text]-PdH phase transition, CO poisoning), limiting the formate production to a narrow potential window of 0V to -0.25V vs. reversible hydrogen electrode (RHE). Herein, we discovered that the Pd surface capped with polyvinylpyrrolidone (PVP) ligand exhibits effective resistance to the potential-depended deactivations and can catalyze formate production at a much extended potential window (beyond -0.7V vs. RHE) with significantly improved activity (~14-times enhancement at -0.4V vs. RHE) compared to that of the pristine Pd surface. Combined results from physical and electrochemical characterizations, kinetic analysis, and first-principle simulations suggest that the PVP capping ligand can effectively stabilize the high-valence-state Pd species (Pdδ+) resulted from the catalyst synthesis and pretreatments, and these Pdδ+species are responsible for the inhibited phase transition from [Formula: see text]-PdH to [Formula: see text]-PdH, and the suppression of CO and H2 formation. The present study confers a desired catalyst design principle, introducing positive charges into Pd-based electrocatalyst to enable efficient and stable CO2 to formate conversion.