Electrocatalytic semi-hydrogenation of acetylene (C2H2) over copper nanoparticles (Cu NPs) offers a promising non-petroleum alternative for the green production of ethylene (C2H4). However, server hydrogen evolution reaction (HER) competition in this process prominently decreases C2H4 selectivity, thereby hindering its practical application. Herein, a Cu-based composite catalyst, wherein porous carbon with nanoscale pores was used as a support, is constructed to gather the C2H2 feedstocks for suppressing the undesirable HER. As a result, the as-prepared catalyst exhibited C2H2 conversion of 27.1% and C2H4 selectivity of 88.4% at a C2H4 partial current density of 0.25 A/cm2 under optimal − 1.0 V versus reversible hydrogen electrode (RHE) under the simulated coal-derived C2H2 atmosphere, significantly outperforming the single Cu NPs counterparts. In addition, a series of in situ and ex situ experimental results show that not only the porous nature of the carbon support but also the stabilized Cu0–Cu+ dual active sites through the strong metal–support interactions enhance the adsorption capacity of C2H2, leading to high C2H2 partial pressure, restraining the HER and thus improving the C2H4 selectivity.
Herein, a novel method for fluorometric detection of soybean trypsin inhibitor (SBTI) activity based on a water-soluble poly(diphenylacetylene) derivative was reported. Fluorescence quenching of the polymer via p-nitroaniline, produced from the trypsin-catalyzed decomposition of N-benzoyl-DL-arginine-4-nitroanilide hydrochloride (L-BAPA), was well described using the Stern–Volmer equation. SBTI activity was quantitatively assessed based on changes in the fluorescence intensity of the polymer. This strategy has several advantages, such as high sensitivity and ease of operation. Moreover, its applicability to other biochemical analyses is promising.
Although doped hole-transport materials (HTMs) offer an efficiency benefit for perovskite solar cells (PSCs), they inevitably diminish the stability. Here, we describe the use of various chlorinated small molecules, specifically fluorenone-triphenylamine (FO-TPA)-x-Cl [x = para, meta, and ortho (p, m, and o)], with different chlorine-substituent positions, as dopant-free HTMs for PSCs. These chlorinated molecules feature a symmetrical donor–acceptor–donor structure and ideal intramolecular charge transfer properties, allowing for self-doping and the establishment of built-in potentials for improving charge extraction. Highly efficient hole-transfer interfaces are constructed between perovskites and these HTMs by strategically modifying the chlorine substitution. Thus, the chlorinated HTM-derived inverted PSCs exhibited superior efficiencies and air stabilities. Importantly, the dopant-free HTM FO-TPA-o-Cl not only attains a power conversion efficiency of 20.82% but also demonstrates exceptional stability, retaining 93.8% of its initial efficiency even after a 30-day aging test conducted under ambient air conditions in PSCs without encapsulation. These findings underscore the critical role of chlorine-substituent regulation in HTMs in ensuring the formation and maintenance of efficient and stable PSCs.
The existence of alkali metals in flue gases originating from stationary sources can result in catalyst deactivation in the low-temperature selective catalytic reduction (SCR) of nitrogen oxides (NO x). It is widely accepted that alkali metal poisoning causes damage to the acidic sites of catalysts. Therefore, in this study, a series of CoMn catalysts doped with heteropolyacids (HPAs) were prepared using the coprecipitation method. Among these, CoMnHPMo exhibited superior catalytic performance for SCR and over 95% NO x conversion at 150–300 ℃. Moreover, it exhibited excellent catalytic activity and stability after alkali poisoning, demonstrating outstanding alkali metal resistance. The characterization indicated that HPMo increased the specific surface area of the catalyst, which provided abundant adsorption sites for NO x and NH3. Comparing catalysts before and after poisoning, CoMnHPMo enhanced its alkali metal resistance by sacrificing Brønsted acid sites to protect its Lewis acid sites. In situ DRIFTS was used to study the reaction pathways of the catalysts. The results showed that CoMnHPMo maintained high NH3 adsorption capacity after K poisoning and then reacted rapidly with NO intermediates to ensure that the active sites were not covered. Consequently, SCR performance was ensured even after alkali metal poisoning. In summary, this research proposed a simple method for the design of an alkali-resistant NH3-SCR catalyst with high activity at low temperatures.
CO2 is the most cost-effective and abundant carbon resource, while the reverse water–gas reaction (rWGS) is one of the most effective methods of CO2 utilization. This work presents a comparative study of rWGS activity for perovskite systems based on AFeO3 (where A = Ce, La, Y). These systems were synthesized by solution combustion synthesis (SCS) with different ratios of fuel (glycine) and oxidizer (φ), different amounts of NH4NO3, and the addition of alumina or silica as supports. Various techniques, including X-ray diffraction analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, energy-dispersive X-ray spectroscopy, N2-physisorption, H2 temperature-programmed reduction, temperature-programmed desorption of H2 and CO2, Raman spectroscopy, and in situ FTIR, were used to relate the physicochemical properties with the catalytic performance of the obtained composites. Each specific perovskite-containing system (either bulk or supported) has its own optimal φ and NH4NO3 amount to achieve the highest yield and dispersion of the perovskite phase. Among all synthesized systems, bulk SCS-derived La–Fe–O systems showed the highest resistance to reducing environments and the easiest hydrogen desorption, outperforming La–Fe–O produced by solgel combustion (SGC). CO2 conversion into CO at 600 °C for bulk ferrite systems, depending on the A-cation type and preparation method, follows the order La (SGC) < Y < Ce < La (SCS). The differences in properties between La–Fe–O obtained by the SCS and SGC methods can be attributed to different ratios of oxygen and lanthanum vacancy contributions, hydroxyl coverage, morphology, and free iron oxide presence. In situ FTIR data revealed that CO2 hydrogenation occurs through formates generated under reaction conditions on the bulk system based on La–Fe–O, obtained by the SCS method. γ-Al2O3 improves the dispersion of CeFeO3 and LaFeO3 phases, the specific surface area, and the quantity of adsorbed H2 and CO2. This led to a significant increase in CO2 conversion for supported CeFeO3 but not for the La-based system compared to bulk and SiO2-supported perovskite catalysts. However, adding alumina increased the activity per mass for both Ce- and La-based perovskite systems, reducing the amount of rare-earth components in the catalyst and thereby lowering the cost without substantially compromising stability.
Improving the efficiency of metal/reducible metal oxide interfacial sites for hydrogenation reactions of unsaturated groups (e.g., C=C and C=O) is a promising yet challenging endeavor. In our study, we developed a Pd/CeO2 catalyst by enhancing the oxygen vacancy (OV) concentration in CeO2 through high-temperature treatment. This process led to the formation of an interface structure ideal for supporting the hydrogenation of methyl oleate to methyl stearate. Specifically, metal Pd0 atoms bonded to the OV in defective CeO2 formed Pd0–OV–Ce3+ interfacial sites, enabling strong electron transfer from CeO2 to Pd. The interfacial sites exhibit a synergistic adsorption effect on the reaction substrate. Pd0 sites promote the adsorption and activation of C=C bonds, while OV preferably adsorbs C=O bonds, mitigating competition with C=C bonds for Pd0 adsorption sites. This synergy ensures rapid C=C bond activation and accelerates the attack of active H* species on the semi-hydrogenated intermediate. As a result, our Pd/CeO2-500 catalyst, enriched with Pd0–OV–Ce3+ interfacial sites, demonstrated excellent hydrogenation activity at just 30 °C. The catalyst achieved a Cis–C18:1 conversion rate of 99.8% and a methyl stearate formation rate of 5.7 mol/(h·gmetal). This work revealed the interfacial sites for enhanced hydrogenation reactions and provided ideas for designing highly active hydrogenation catalysts.
N-doped carbon materials, with their applications as electrocatalysts for the oxygen reduction reaction (ORR), have been extensively studied. However, a negletcted fact is that the operating potential of the ORR is higher than the theoretical oxidation potential of carbon, possibly leading to the oxidation of carbon materials. Consequently, the influence of the structural oxidation evolution on ORR performance and the real active sites are not clear. In this study, we discover a two-step oxidation process of N-doped carbon during the ORR. The first oxidation process is caused by the applied potential and bubbling oxygen during the ORR, leading to the oxidative dissolution of N and the formation of abundant oxygen-containing functional groups. This oxidation process also converts the reaction path from the four-electron (4e) ORR to the two-electron (2e) ORR. Subsequently, the enhanced 2e ORR generates oxidative H2O2, which initiates the second stage of oxidation to some newly formed oxygen-containing functional groups, such as quinones to dicarboxyls, further diversifying the oxygen-containing functional groups and making carboxyl groups as the dominant species. We also reveal the synergistic effect of multiple oxygen-containing functional groups by providing additional opportunities to access active sites with optimized adsorption of OOH*, thus leading to high efficiency and durability in electrocatalytic H2O2 production.