Search

The electrochemical CO2 reduction reaction (eCO2RR) to multicarbon products has been widely recognized for Cu‐based catalysts. However, the structural changes in Cu‐based catalysts during the eCO2RR pose challenges to achieving an in‐depth understanding of the structure–activity relationship, thereby limiting catalyst development. Herein, we employ constant‐potential density functional theory calculations to investigate the sintering process of Cu single atoms of Cu−N−C single‐atom catalysts into clusters under eCO2RR conditions. Systematic constant‐potential ab initio molecular dynamics simulations revealed that the leaching of Cu−(CO)x moieties and subsequent agglomeration into clusters can be facilitated by synergistic adsorption of H and eCO2RR intermediates (e.g. CO). Increasing the Cu2+ concentration or the applied potential can efficiently suppress Cu sintering. Both microkinetic simulations and experimental results further confirm that sintered Cu clusters play a crucial role in generating C2 products. These findings provide significant insights into the dynamic evolution of Cu‐based catalysts and the origin of their activity toward C2 products during the eCO2RR. [ABSTRACT FROM AUTHOR]

Process preparation route of ESM/Cu 2 O and photocatalytic mechanism under visible light. [Display omitted] • The surface of eggshell membrane (ESM) is favorable for Cu2+ adsorption. • Cu 2 O prepared by using ESM as a carrier possesses uniform size, good dispersibility and excellent photocatalytic activity. • Cu 2 O containing oxygen defects effectively promotes the separation of photogenerated electrons and holes. The conversion of biological waste into high-value-added materials is of great significance for environmental protection and sustainable economic development. Metal nanoparticles should be used in the field of photocatalysis because of their excellent photocatalytic activity and wide selectivity. Green and sustainable carriers play an important role in improving the utilization and recycling of nanoparticles. In this work, we synthesized eggshell membrane (ESM)/ cuprous oxide biomass catalysts from biological eggshell membranes using a biotemplate method, and the biomass catalysts showed an interwoven network structure of uniformly loaded nanoparticles. The results showed that these biomass composites had good photocatalytic activity (kapp = 0.0392 min−1) for methylene blue (MB), and the eggshell membranes acted as a sacrificial agent during the catalytic process, which effectively inhibited the compounding rate of photogenerated electrons. The photodegradation rate reached about 97 % in 1 h when the adsorbent dosage was 0.025 g, and the dye concentration was 30 mg/L. The present work is important for realizing the integration of biomaterials science and nanoscience. [ABSTRACT FROM AUTHOR]

A highly efficient, catalyst-free and one-pot procedure for the direct synthesis of amides from aldehydes and amines under mild conditions has been developed. Both aliphatic and aromatic aldehydes with primary or secondary amines are successfully converted to the corresponding amides, and it is observed that reactions can proceed in either aqueous or organic media. [ABSTRACT FROM AUTHOR]

[Display omitted] • The small Au NPs on CeO 2 are thermodynamically less stable than Au SAs in the presence of CO at typical reaction conditions. • There is a good linear relationship between the vibrational frequency of adsorbed CO and the oxidation states of Au atoms. • The dislodgement of Au(CO) complex strongly depends on the local topology of Au/CeO 2 interface. Single-atom catalysis is at the center of the attention of the heterogeneous catalysis community. It remains a challenge to determine the thermodynamic stability of single atoms on an oxide support and compare their activity to that of small clusters and nanoparticles. We conducted density functional theory calculations to compare the stability of Au(CO) complexes on the CeO 2 (1 1 1) terrace and step-edge of CeO 2 (1 1 1) against CeO 2 (11 1)-supported nanoparticles. The different single atom Au and Au cluster models were compared for CO oxidation at low temperature. Trapped as dopants substituting for Ce in the surface or in a ceria O vacancy, Au cannot catalyze CO oxidation. Single Au atoms at step-edges represent candidate active sites for low-temperature CO oxidation. The CO oxidation at the interface between Au nanoparticles and CeO 2 can directly take place through a Mars-van Krevelen mechanism and account for a promising reactivity when the dislodgment of Au(CO) complex is hindered. The possibility of CO-induced dislodgement of a single Au atom depends critically on the topology of the Au-CeO 2 interface. [ABSTRACT FROM AUTHOR]

Graphical abstract Functionalized Fe-TCNQ monolayers serve as high-performance bifunctional ORR/OER catalysts. Highlights • A low limiting overpotential of 0.33 V for Fe-TCNQ is predicted toward ORR. • The catalytic performance of Ni-TCNQs monolayer is identified as the highest for OER. • By grafting ligands and applying strain, the adsorption strengths can be optimized. • Fe-TCNQ-Cl is predicted as high-activity bifunctional ORR/OER catalysts. Abstract The identification of catalytically active and stable bifunctional electrocatalysts for the oxygen reduction and evolution reaction (ORR/OER) would revolutionize rechargeable metal-air batteries and regenerative fuel cell technologies. In this study, we use density functional theory (DFT) calculations to systemically investigate 2D transition metal based tetracyanoquinodimethane (TM–TCNQ, TM = Cr-Cu, Ru-Ag, Pt, Ir) monolayers with single TM atoms catalysts (SACs) distributed periodically with high density. We calculate a lower limiting overpotential of η lim = 0.33 V for Fe-TCNQ yielding a higher expected activity than that of Pt metal (0.48 V) for the ORR under acidic conditions. The catalytic performance of Fe-TCNQ for OER is, however, surpassed by Ni-TCNQs (η lim = 0.46 V), which is identified as the highest among the candidates. By applying grafting axial ligands and external strain, the adsorption strength of reaction intermediates on TM reactive sites can be further optimized and enhances the activities of Mn-, Fe- and Ni-TCNQs for the ORR or the OER. Here, Fe-TCNQ-Cl (η lim = 0.27/0.55 V), followed by Fe-TCNQ-CO (η lim = 0.67/0.43 V), are predicted as novel, high-performance bifunctional ORR/OER catalysts with comparable limiting overpotentials to those of the best commercially used electrocatalysts, Pt (ORR: η lim = 0.48 V) and RuO 2 (OER: η lim = 0.42 V). In addition, the recently synthesized Fe-TCNQ possess excellent conductivity with fast electron transfer during the catalytic reactions. These results show 2D TM-TCNQ monolayers are durable, low-cost, and efficient catalysts for the ORR and the OER in metal-air batteries and fuel cells. [ABSTRACT FROM AUTHOR]

A theoretical study on modulation of local coordination environment of main group metals in M−N−C catalysts toward oxygen reduction reaction (ORR) has been conducted. DFT results show that MgN 2 O 2 is at the peak of the volcano, which is ascribed to more shifts of p-band position of Mg away from the Fermi energy level and the lower O highest occupied energy level. [Display omitted] • MgN 2 O 2 is a promising candidate for oxygen reduction reaction; • The lower ORR overpotential on MgN 2 O 2 is ascribed to more shifts of p-band position of Mg and the lower O highest occupied energy level of OH*; • There is a linear relationship between adsorption free energies of OH* and O highest occupied energy levels of OH*. For the 4e– oxygen reduction reaction (ORR) on main group metal-nitrogen-carbon catalysts, the effect of the local coordination environment of main group metals on ORR has rarely been reported. By performing density functional theory (DFT) calculations, we screen 18 MN 4–x O x (x = 0–2, M = Mg, Ca, Sr, Al, Ga, In) candidates with different metal coordination environments and construct volcano curve between the adsorption free energy of OH* (ΔG OH*) and ORR overpotential, yielding MgN 2 O 2 at the peak of the volcano with the overpotential as low as 0.55 V. The lower ORR overpotential on Mg coordinated with 2 N and 2 O atoms than other coordination environments is well explained by the decreased ΔG OH* because of more shifts of p-band position of Mg away from the Fermi energy level as well as the lower O highest occupied energy level when the number of the coordinated O atoms increases. Our DFT work provides theoretical guidance for engineering ORR performance of main group metal-nitrogen-carbon catalysts by modulating coordination environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three kinds of Mn-based mullite nanofibers with different A‐sites were synthesized by a facile electrospinning method. • A‐site substitution exhibited an important role in the catalytic performance of mullite catalyst. • Structure-activity relationships evidenced that surface adsorbed oxygen and reducibility contributed greatly to superior activity of SmMn 2 O 5 catalyst. Mullite was one of the most promising catalysts that used in the selective catalytic oxidation of NO (NO-SCO), and deciphering its intrinsic properties that affect the catalytic performance was a great challenge but critical to the development of mullite catalysts. Herein, a series of Mn-based mullite nanofibers with different A-site cations were synthesized by electrospinning method and used for catalytic NO oxidation. Activity tests showed that SmMn 2 O 5 exhibited a better NO conversion rate (77.8 %) than those of PrMn 2 O 5 (63.3 %) and YMn 2 O 5 (57.5 %) under typical experimental conditions (GHSV = 120 000 h−1, T = 325 °C). To investigate the factors influencing the catalytic activity, various techniques including XRD, N 2 adsorption, SEM, TEM, EDX, XPS, H 2 -TPR, and O 2 -TPD were employed, and the results showed that abundant surface adsorbed oxygen species and good reducibility contributed greatly to the catalytic performance of SmMn 2 O 5. DFT calculations revealed that A-site cation played the decisive role in the Fermi level relative to the Mn 3d -band centre, thus affecting the adsorption and dissociation of O 2 molecule. The present synthetic strategy offered a new viable route for the large-scale preparation of metal oxide catalysts with remarkable NO oxidation performance for practical application. [ABSTRACT FROM AUTHOR]