High Valence Research Articles

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.

The design of high-entropy metal sulfides promising high-performance gaseous elemental mercury removal

Regulating the surface coordination environment and improving the formation of active species represent the key factor in designing high-performance metal sulfide-based sorbents for gaseous Hg0 capture. This paper reported the Hg0 adsorption by high entropy metal sulfides for the first time, and clarified the mechanisms involved in the evolutions of active species as well as the Hg0 adsorption. The multiple metal components of the high entropy metal sulfides have great significance in improving the surface chemistry. The addition of Ce helps not only the formation of chemically homogeneous structure, but also the generation of high valence state metal cations and unsaturated sulfur species, thereby improving obviously the Hg0 removal ability. The synthesized CeNiCoMnCuSx has a high Hg0 adsorption capacity of 10.52 mg·g−1 at 80 %-breakthrough, and a Hg0 adsorption rate of 4.31 μg·g−1·min−1. The high valence state metal cations (Ni3+, Co3+, Mn4+, Cu2+ and Ce4+) and unsaturated Sx2− and S22− species can directly oxidize Hg0 and convert it into HgS. In comparison, the quaternary sulfide counterpart (NiCoMnCuSx) cannot form a main phase structure, and has obviously lower percentages of high valence state metal cations and unsaturated sulfur species. This work provides a new space for developing metal sulfides for Hg0 adsorption.

Performance and mechanism analysis of sludge-based biochar loaded with Co and Mn as photothermal catalysts for simultaneous removal of acetone and NO at low temperature.

Replacing NH3 in NH3-SCR with VOCs provides a new idea for the simultaneous removal of VOCs and NOx, but the technology still has urgent problems such as high cost of catalyst preparation and unsatisfactory catalytic effect in the low-temperature region. In this study, biochar obtained from sewage sludge calcined at different temperatures was used as a carrier, and different Co and Mn injection ratios were selected. Then, a series of sludge-based biochar (SBC) catalysts were prepared by a one-step hydrothermal synthesis method for the simultaneous removal of acetone and NO in a low-temperature photothermal co-catalytic system with acetone replacing NH3. The characterization results show that heat is the main driving force of the reaction system, and the abundance of Co and Mn atoms in high valence states, surface-adsorbed oxygen, and oxygen lattice defects in the catalyst are the most important factors affecting the performance of the catalyst. The performance test results showed that the optimal pyrolysis temperature of sludge was 400 °C, the optimal dosing ratio of Co and Mn was 4:1, and the catalyst achieved 42.98% and 52.41% conversion of acetone and NO, respectively, at 240 °C with UV irradiation. Compared with the pure SBC without catalytic effect, the SBC loaded with Co and Mn gained the ability of simultaneous removal of acetone and NO through the combined effect of multiple factors. The key reaction steps for the catalytic conversion of acetone and NO on the catalyst surface were investigated according to the Mars-van Krevelen (MvK) mechanism, and a possible mechanism was proposed. This study provides a new strategy for the resource utilization of sewage sludge and the preparation of photothermal catalysts for the simultaneous removal of acetone and NO at low cost.

First-principles study on the properties of Ta doped P2-Na2/3Fe1/3Mn2/3O2 for Na-ion batteries

P2-Na2/3Fe1/3Mn2/3O2 (NFM) is a layered transition material with abundant raw materials, high specific capacity, and excellent cycling stability, a potential cathode material for sodium-ion batteries. The considerable size and substantial mass of Na+ present notable challenges concerning unfavorable reaction kinetics and structural instability during the insertion and extraction processes. This presents a formidable obstacle for practical applications. Ta5+ is characterized by higher valence and more muscular bonding energy, and doping Ta in NFM leads to the formation of a stable crystal structure. In the present work, we use first-principles calculations within the DFT + U framework to investigate different concentrations of Ta-doped MFMs to overcome these drawbacks. The calculated results show that the introduction of Ta elements reduces the formation energy and enhances the structural stability. It also enhances the electronic conductivity (i.e., the band gap, Eg = 0) and lowers the ion mobility barrier. In addition, we also investigate the electronic structure, spin, and magnetic properties of doping controlled electrode materials to investigate the doping effect regulating migration energy barriers. This study suggests that Ta-doped NFMT is a good alternative due to higher performance compared to the pristine NFM.

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Insights into chromium removal mechanism by Ca-based sorbents from flue gas

Chromium is a typical toxic pollution in sewage sludge incineration flue gas. Cr removal from flue gas is a challenge due to the high toxicity and valence variability of chromium. Ca-based sorbents, including CG-CaO, CA-CaO, and CCi-CaO, were developed for Cr capture by calcining calcium D-gluconate monohydrate, calcium acetate hydrate, and calcium citrate tetrahydrate, respectively. CG-CaO, CA-CaO, and CCi-CaO exhibit better Cr removal performance than traditional CaO. CA-CaO shows superior Cr adsorption ability due to the large BET surface area and pore volume. The Cr adsorption efficiency of CA-CaO is up to 94.79 % at 1000 °C. XRD and XPS results reveal that the adsorbed Cr contains Cr(III) and Cr(VI), and exists in the form of CaCr2O4 and CaCrO4. Cr adsorption on Ca-based sorbents is mainly controlled by adsorption and oxidation mechanism. The adsorption process of Cr on different Ca-based sorbents was described by four typical adsorption kinetic models. For CaO and CG-CaO, pseudo-first order model and Elovich model are suitable for the description of Cr adsorption. For CA-CaO and CCi-CaO, pseudo-second order model, Elovich model and Weber and Morris model fit well with the experimental values of Cr adsorption, suggesting that Cr adsorption on CA-CaO and CCi-CaO is controlled by a combined mechanism of chemisorption and intraparticle diffusion. The saturated adsorption capacity of CaO, CG-CaO, CA-CaO and CCi-CaO are evaluated to be 39.77, 48.98, 102.22 and 104.52 mg/g, respectively. The effects of incineration flue gas components on Cr adsorption were also explored. O2 shows no obvious influence on Cr adsorption over CA-CaO. HCl, SO2, NO and CO2 can inhibit Cr adsorption because of the competitive adsorption, and the inhibitory effect of SO2 is the strongest.

The In Situ Construction of NiFeS on Stainless Steel Mesh as an Efficient Electrocatalyst for UOR

Urea can be used as an effective hydrogen energy carrier, the development of efficient and stable anodic electrocatalysts for urea oxidation reaction (UOR) was crucial for achieved energy-saving hydrogen-production. Nanoflower like structures electrocatalysts have attracted increasing research interests due to its structural advantages. In this article, NiFeS/SSM with two dimensions (2D) nanosflower like structures in situ growth on three dimensions (3D) stainless steel mesh (SSM) is prepared by step-wise hydrothermal method. NiFeS/SSM was derived from NiFe layered double hydroxides, and the as-prepared electrode was directly served as a electrocatalysts for UOR. Benefiting from the electronic effect between Ni and Fe components which promotes the formation of the high valence Ni species in the NiFeS/SSM catalyst, the tuning effect from the in situ generated sulfate and its open 3D porous structure for SSM basement. The electrode displayed excellent catalytic activities towards UOR, the overpotential for UOR are 1.08 V in alkaline electrolyte at 50 mA·cm−2. This work not only illustrated that non-noble metal-based electrocatalysts have tremendous potential applications for electrocatalytic electrolysis of urea but also provided a feasible strategy to prepare high-efficiency and stable non-precious metal UOR anode catalysts in alkaline medium.

Effect of Added Natural and Artificial Sounds on Emotional Response and Indoor Soundscape to Residential Noises

This study investigated the effect of added natural and artificial sounds on emotional responses due to residential noises. The laboratory experiment conducted on three residential noise sources (child jumping and plumbing from upper unit and air conditioner outdoor unit) with different sound spectrum and temporal characteristics. In addition, combined sounds with residential, natural (one birdsong and three water sounds of waterfall, sea wave, and stream) and artificial sound (brown and white noise) were set. The experiment consisted of two sessions; self-assessment manikin and indoor soundscape assessment for each sound sources (single and combined residential noises) presented by headphone and woofer. As a result, most combined natural and artificial sounds resulted in more positive changes (higher valence and lower arousal score) than single residential noise. Among combined sounds, multiple natural sound (birdsong + stream) with residential noise showed significant difference from single residential noises such as air conditioner outdoor unit and plumbing noise. Meanwhile, eight affective attribute scale for indoor soundscape assessment showed two main perceptual dimensions and most added natural and artificial sounds had a role in increasing comfort.

Emotional response to natural and artificial sound and indoor sound scape in residential space

The demand for effective ways to alleviate stress caused by residential noise is growing. To better understand individual preferences and strategies for reducing noise-induced stress, a laboratory experiment was conducted to classify emotional responses to natural and artificial sounds according to individual characteristics. The survey consisted of two sessions conducted after collecting individual characteristics from participants. Session 1 evaluated preference for sound sources and emotional responses to sound presented from headphone and woofer by using the self-assessment manikin (SAM). Session 2 utilized to assess indoor soundscape. The results showed that both valence and arousal were highly correlated with sound preference, with higher valence and lower arousal tending to be more preferred. In the case of indoor soundscape assessment, water sounds showed significant differences between PC1 and PC2 on the comfortable-annoying axis and the intrusive-uncontrolled axis.

Controllable construction of bifunctional sites on Ir@Ni/NiO core/shell porous nanorod arrays for efficient water splitting

Ir-modified Ni/NiO core/shell porous nanorod arrays (Ir@Ni/NiO PNAs) are constructed for efficient alkaline full water splitting via a simple and controllable electro-etching process, where the introduced Ir tunes electronic structure of NiO and builds unique bifunctional Ir-Ni3+ catalytic sites. Specially, the high current density during electro-etching dominates the Ir modification and casting of bifunctional Ir-Ni3+ sites. Ir serves as the active site in a high valence state and cooperates with Ni3+ to catalyze the OER. Meanwhile, Ir promotes the recombination of Had while Ni3+ as the co-catalyst accelerates the cleavage of the H-OH bond, which jointly improve the HER activity. Ir@Ni/NiO exhibits extraordinary overall water splitting performance, with an overpotential of 193.8 mV for OER and 54.7 mV for HER at 10 mA cm−2. Furthermore, the two-electrode cell assembled with Ir@Ni/NiO requires only a low cell voltage of 1.50 V to achieve a current density of 10 mAcm−2, outperforming the commercial IrO2 and Pt. This work blazes the trail for the rational design of water-splitting catalysts and the advancement of alkaline water-splitting for hydrogen production.

Electrophysiological correlates of the emotional response on brain activity in adolescents

Many studies have attempted to analyze the main neurophysiological characteristics of emotional response, but few have been carried out at early ages, including adolescence or early adulthood. The main objective of the present study is to assess the electrophysiological correlates of emotional response in adolescents and young adults through electroencephalography (EEG) measures. Sample, composed of 25 subjects (18.44 ± 0.71 years old), were exposed to different sequences of images belonging to the IAPS, which were selected following the dimensional model, based on their valence and arousal, while their neural activity was evaluated through EEG. Results indicated differences in cortical neural activity in response to the valence of the images and the level of arousal. Specifically, we observed that exposure to positive images (high valence) with high arousal produced an increase in alpha, beta, and delta wave activity but not in theta activity. In the case of positive images with low arousal, however, the results indicated an increase in beta waves only and a decrease in alpha, delta, and theta activity. For negative images (low valence) with high arousal, an increase in alpha, beta, and delta waves but not in theta was observed, while negative images with low arousal induced an increase in beta, delta, and theta wave response. This study demonstrates that activated cortical areas indicated significant differences based on the different emotional responses in adolescents and young adults.

Convergent synthesis of a hexadecavalent heterobifunctional ABO blood group glycoconjugate

Naturally occurring glycans are often found in a multivalent presentation. Cell surface receptors that recognize these displays may form clusters, which can lead to signalling or endocytosis. One of the challenges in generating synthetic displays of multivalent carbohydrates is providing high valency as well as access to heterofunctional conjugates to allow attachment of multiple antigens or payloads. We designed a strategy based on a set of bifunctional linkers to generate a heterobifunctional multivalent display of two carbohydrate antigens to bind BCR and CD22 with four and twelve antigen copies, respectively. We confirmed that the conjugates were able to engage both CD22 and BCR on cells by observing receptor clustering. The strategy is modular and would allow for alternative carbohydrate antigens to be attached bearing amine and alkyne groups and should be of interest for the development of immunomodulators and vaccines.

Uncovering a CF3 Effect on X-ray Absorption Energies of [Cu(CF3 )4 ]- and Related Copper Compounds by Using Resonant Diffraction Anomalous Fine Structure (DAFS) Measurements.

Understanding the electronic structures of high-valent metal complexes aids the advancement of metal-catalyzed cross coupling methodologies. A prototypical complex with formally high valency is [Cu(CF3 )4 ]- (1), which has a formal Cu(III) oxidation state but whose physical analysis has led some to a Cu(I) assignment in an inverted ligand field model. Recent examinations of 1 by X-ray spectroscopies have led previous authors to contradictory conclusions, motivating the re-examination of its X-ray absorption profile here by a complementary method, resonant diffraction anomalous fine structure (DAFS). From analysis of DAFS measurements for a series of seven mononuclear Cu complexes including 1, here it is shown that there is a systematic trifluoromethyl effect on X-ray absorption that blue shifts the resonant Cu K-edge energy by 2-3 eV per CF3 , completely accounting for observed changes in DAFS profiles between formally Cu(III) complexes like 1 and formally Cu(I) complexes like (Ph3 P)3 CuCF3 (3). Thus, in agreement with the inverted ligand field model, the data presented herein imply that 1 is best described as containing a Cu(I) ion with dn count approaching 10.

Uncovering a CF3 Effect on X‐ray Absorption Energies of [Cu(CF3)4]− and Related Copper Compounds by Using Resonant Diffraction Anomalous Fine Structure (DAFS) Measurements**

AbstractUnderstanding the electronic structures of high‐valent metal complexes aids the advancement of metal‐catalyzed cross coupling methodologies. A prototypical complex with formally high valency is [Cu(CF3)4]− (1), which has a formal Cu(III) oxidation state but whose physical analysis has led some to a Cu(I) assignment in an inverted ligand field model. Recent examinations of 1 by X‐ray spectroscopies have led previous authors to contradictory conclusions, motivating the re‐examination of its X‐ray absorption profile here by a complementary method, resonant diffraction anomalous fine structure (DAFS). From analysis of DAFS measurements for a series of seven mononuclear Cu complexes including 1, here it is shown that there is a systematic trifluoromethyl effect on X‐ray absorption that blue shifts the resonant Cu K‐edge energy by 2–3 eV per CF3, completely accounting for observed changes in DAFS profiles between formally Cu(III) complexes like 1 and formally Cu(I) complexes like (Ph3P)3CuCF3 (3). Thus, in agreement with the inverted ligand field model, the data presented herein imply that 1 is best described as containing a Cu(I) ion with dn count approaching 10.

Release Kinetics of Potassium, Calcium, and Iron Cations from Carboxymethyl Cellulose Hydrogels at Different pH Values.

In an in-depth study of the mechanism of cation release from carboxymethyl cellulose hydrogels synthesized through Schiff base reaction, we analyze the differences in the release kinetics of potassium, calcium, and iron cations with Peleg model at pH values of pH 3.5 and pH 8.5 using ICP-OES (inductively coupled plasma optical emission spectroscopy) technique.

A salt-induced tackifying polymer for enhancing oil recovery in high salinity reservoirs: Synthesis, evaluation, and mechanism

Polymer flooding is an effective method widely applied for enhancing oil recovery (EOR) by reducing the mobility ratio between the injected water and crude oil. However, traditional polymers encounter challenges in high salinity reservoirs due to their salt sensitivity. To overcome this challenge, we synthesized a zwitterion polymer (PAMNS) with salt-induced tackifying property through copolymerization of acrylamide and a zwitterion monomer, methylacrylamide propyl-N, N-dimethylbutylsulfonate (NS). NS monomer is obtained from the reaction between 1,4-butanesultone and dimethylamino propyl methylacrylamide. In this study, the rheological properties, salt responsiveness, and EOR efficiency of PAMNS were evaluated. Results demonstrate that PAMNS exhibits desirable salt-induced tackifying characteristics, with viscosity increasing up to 2.4 times as the NaCl concentration reaches a salinity of 30 × 104 mg L−1. Furthermore, high valence ions possess a much stronger effect on enhancing viscosity, manifested as Mg2+ > Ca2+ > Na+. Molecular dynamics simulations (MD) and fluid dynamics experiment results demonstrate that PAMNS molecules exhibit a more stretched state and enhanced intermolecular associations in high-salinity environments. It is because of the salt-induced tackifying, PAMNS demonstrates superior performance in polymer flooding experiments under salinity ranges from 5 × 104 mg L−1 to 20 × 104 mg L−1, leading to 10.38–19.83% higher EOR than traditional polymers.

Multifunctional 0D@2D (Mox-Mn)Sy-NPs@MXene hybrid electrode with high rate-capability and ultra-long cycling life for Li-ion battery and all Molybdenum-MXene-based 1.9 (V) asymmetric supercapacitor

0D@2D heterostructures constituted by binary transition metal sulfides@transition metal carbides can illustrate the combined advantages of each material with their improved electrochemical performance for energy storage devices. 2D transition metal carbides (MXene ∼ Ti3C2) have presented themselves as the most appropriate candidates for the construction of lower-dimensional 0D ∼ like electroactive nanoparticles (NPs). Due to the high theoretical capacity values and versatile valence states, the molybdenum incorporated mixed metal sulfides ((Mox-Mn)Sy) nanoparticles decorated over 2D Ti3C2 sheets are reported for Li-ion battery and asymmetric supercapacitor. A uniquely designed (Mox-Mn)Sy-NPs@MXene hybrid material displays a high Li-ion storage capacity of up to 698 mA h g−1 at 50 mA g−1, and a commendable areal capacity performance (∼1.27 mA h cm−2 at 2 mA cm−2) for supercapacitor, along with outstanding capacity retention at higher current density and stable cycling performance. Furthermore, a 0D@2D (Mo-Fe7)Sx-NPs@MXene hybrid material is utilized as anode material to construct a coin cell-like (Mox-Mn)Sy-NPs@MXene//(Mo-Fe7)Sx-NPs@MXene asymmetric supercapacitor (ASC) device. A high-voltage (∼1.90 V) ASC device based on unique 0D@2D heterostructures displays an ultra-high energy density of 78.8 W h Kg−1 at a power density of 634.63 W Kg−1 along with maximum specific capacity retention and cycling stability performance. This study emphasizes the importance of 0D@2D based heterostructure materials for the development of efficient energy storage devices.

Enhanced Carrier Dynamics of CsPbBr3 Nanocrystals Enabled by Short-Ligand Ethanedithiol for Efficient Photoelectrocatalytic Photoanodes.

Photoelectrochemical (PEC) water splitting is a potential solution for a low-carbon society and clean energy storage due to its ability to produce hydrogen and oxygen. However, the slow oxidation half-reaction of the process has limited its overall efficacy, necessitating the development of an efficient photoanode. Colloidal CsPbBr3 nanocrystals (NCs) have been identified as promising candidates due to their high light absorption and valence band position. However, the presence of the electrical insulator, long-chain oleate molecules, on the surface of the CsPbBr3 NCs has hindered efficient charge carrier separation and transport. To solve this problem, short-chain 1,2-ethanedithiol (EDT) ligands were used to replace the oleate ligands on the surface of the CsPbBr3 NCs through a solid-state ligand exchange method. This resulted in a reduction of the nanocrystal spacing and a cross-linking reaction, which improved the photogenerated carrier separation and transport while still passivating the dangling bonds on the CsPbBr3 NC surface. Ultimately, this led to a remarkable photocurrent density of 3.34 mA cm-2 (1.23 VRHE), which was 5.2 times higher than that of the pristine oleate-CsPbBr3 NC (0.64 mA cm-2)-based device. This work presents an efficient way of developing inorganic lead halide perovskite colloidal nanocrystal-based photoanodes through surface ligand engineering.

Tailoring the electrochemical reduction kinetics of dual-phase BaCe0.5Fe0.5O cathode via incorporating Mo for IT-SOFCs

The BaCe0.5Fe0.5O3-δ (BCF) cathode consists of the ion-electron mixed conducting phase BaCe0.15Fe0.85O3-δ (BCF1585) and the proton-conducting phase BaCe0.85Fe0.15O3-δ (BCF8515). In this paper, the electrochemical performance is improved by incorporating the high valence element Mo into the BCF and applied to intermediate-temperature solid oxide fuel cells (IT-SOFCs). High-temperature X-ray diffraction (HT-XRD) and O2-temperature programmed desorption (O2-TPD) results show that Mo doping enhances the structural stability of BCF. The X-ray photoelectron spectroscopy (XPS) results suggest that the introduction of Mo increases the amount of adsorbed oxygen and thus the oxygen reduction reaction (ORR) catalytic activity. Compared to BCF, the polarization impedance of BaCe0.5Fe0.45Mo0.05O3-δ (BCFM) at 800°C is 0.154 Ω·cm2, a reduction of 22%. Meanwhile, the BCFM output power at 800°C is 778.01 mW·cm-2, an improvement of 32.17%, and maintains a stable current density after 250 h at 0.7 V. The results demonstrate that Mo doping is an effective strategy to enhance the electrochemical performance of BCF.

Post diversity: A new lens of social media WOM

Social media word of mouth (WOM) involves much interaction and engagement between users in their own networks. The feature of reposting on social media allows WOM to spread fast and easily. Original posts or reposts can be easily identified, perceived, and processed by social media users for purchase decisions. Then, we propose to investigate social media WOM post diversity, which reflects the variation of posts. Further, we propose that the relationship between social media WOM post diversity and sales can be conditional on the three previously established dimensions: volume, valence, and variance. The findings, reflecting approximately 1.5 million posts about 51 movies on a social media site, suggest that WOM post diversity, as measured by post entropy, positively associates with movie sales, contingent on low WOM volume, high valence, and high variance.