More Like this

1. Atomically Dispersed Dual‐Metal Site Catalysts for Enhanced CO ₂ Reduction: Mechanistic Insight into Active Site Structures

   https://doi.org/10.1002/anie.202205632  

   Li, Yi; Shan, Weitao; Zachman, Michael_J; Wang, Maoyu; Hwang, Sooyeon; Tabassum, Hassina; Yang, Juan; Yang, Xiaoxuan; Karakalos, Stavros; Feng, Zhenxing; et al (May 2022, Angewandte Chemie International Edition)

   Abstract Carbon‐supported nitrogen‐coordinated single‐metal site catalysts (i.e., M−N−C, M: Fe, Co, or Ni) are active for the electrochemical CO₂reduction reaction (CO₂RR) to CO. Further improving their intrinsic activity and selectivity by tuning their N−M bond structures and coordination is limited. Herein, we expand the coordination environments of M−N−C catalysts by designing dual‐metal active sites. The Ni‐Fe catalyst exhibited the most efficient CO2RR activity and promising stability compared to other combinations. Advanced structural characterization and theoretical prediction suggest that the most active N‐coordinated dual‐metal site configurations are 2N‐bridged (Fe‐Ni)N₆, in which FeN₄and NiN₄moieties are shared with two N atoms. Two metals (i.e., Fe and Ni) in the dual‐metal site likely generate a synergy to enable more optimal *COOH adsorption and *CO desorption than single‐metal sites (FeN₄or NiN₄) with improved intrinsic catalytic activity and selectivity. 

   more » « less
2. Precursor-mediated in situ growth of hierarchical N-doped graphene nanofibers confining nickel single atoms for CO ₂ electroreduction

   https://doi.org/10.1073/pnas.2219043120  

   Wang, Huan; Li, Youzeng; Wang, Maoyu; Chen, Shan; Yao, Meng; Chen, Jialei; Liao, Xuelong; Zhang, Yiwen; Lu, Xuan; Matios, Edward; et al (April 2023, Proceedings of the National Academy of Sciences)

   Despite the various strategies for achieving metal–nitrogen–carbon (M–N–C) single-atom catalysts (SACs) with different microenvironments for electrochemical carbon dioxide reduction reaction (CO 2 RR), the synthesis–structure–performance correlation remains elusive due to the lack of well-controlled synthetic approaches. Here, we employed Ni nanoparticles as starting materials for the direct synthesis of nickel (Ni) SACs in one spot through harvesting the interaction between metallic Ni and N atoms in the precursor during the chemical vapor deposition growth of hierarchical N-doped graphene fibers. By combining with first-principle calculations, we found that the Ni-N configuration is closely correlated to the N contents in the precursor, in which the acetonitrile with a high N/C ratio favors the formation of Ni-N 3 , while the pyridine with a low N/C ratio is more likely to promote the evolution of Ni-N 2 . Moreover, we revealed that the presence of N favors the formation of H-terminated edge of sp 2 carbon and consequently leads to the formation of graphene fibers consisting of vertically stacked graphene flakes, instead of the traditional growth of carbon nanotubes on Ni nanoparticles. With a high capability in balancing the *COOH formation and *CO desorption, the as-prepared hierarchical N-doped graphene nanofibers with Ni-N 3 sites exhibit a superior CO 2 RR performance compared to that with Ni-N 2 and Ni-N 4 ones. 

   more » « less
3. Computational Screening of Efficient Single‐Atom Catalysts Based on Graphitic Carbon Nitride (g‐C ₃ N ₄ ) for Nitrogen Electroreduction

   https://doi.org/10.1002/smtd.201800368  

   Chen, Zhe; Zhao, Jingxiang; Cabrera, Carlos R.; Chen, Zhongfang (December 2018, Small Methods)

   Abstract The development of low‐cost and efficient electrocatalysts for nitrogen reduction reaction (NRR) at ambient conditions is crucial for NH₃synthesis and provides an alternative to the traditional Harber‐Bosch process. Herein, by means of density functional theory (DFT) computations, the catalytic performance of a series of single metal atoms supported on graphitic carbon nitride (g‐C₃N₄) for NRR is evaluated. Among all the candidates, the Gibbs free energy change of the potential‐determining step for five single‐atom catalysts (SACs), namely Ti, Co, Mo, W, and Pt atoms supported on g‐C₃N₄monolayer, is lower than that on the Ru(0001) stepped surface. In particular, the single tungsten (W) atom anchored on g‐C₃N₄(W@g‐C₃N₄) exhibits the highest catalytic activity toward NRR with a limiting potential of −0.35 V via associative enzymatic pathway, and can well suppress the competing hydrogen evolution reaction. The high NRR activity and selectivity of W@g‐C₃N₄are attributed to its inherent properties, such as significant positive charge and large spin moment on the W atom, excellent electrical conductivity, and moderate adsorption strength with NRR intermediates. This work opens up a new avenue of N₂reduction for renewable energy supplies and helps guide future development of single‐atom catalysts for NRR and other related electrochemical process. 

   more » « less
4. Prediction of Potential-Dependent Kinetics for the Electrocatalytic Reduction of CO ₂ to CO over Ti@4N-Gr

   https://doi.org/10.1021/acselectrochem.4c00073  

   Alsunni, Yousef A; Alherz, Abdulaziz W; Musgrave, Charles B (November 2024, ACS Electrochemistry)

   Grand canonical density functional theory (GC-DFT) was employed to model the electrocatalytic reduction of CO2 (CO2R) to CO by single titanium atom nitrogen-doped graphene, referred to as Ti@4N-Gr. Previous GC-DFT thermodynamic investigations have identified Ti@4N-Gr as a promising CO2R catalyst; however, no in-depth studies have examined it. In this study, we analyze activation energies of the elementary steps at various applied potentials in addition to thermodynamics of CO2R to CO catalyzed by Ti@xN-Gr defects. Reaction intermediates are predicted to be destabilized when Ti is coordinated to fewer N atoms. Based on reaction thermodynamics, Ti@4N-Gr and all defect configurations are predicted to be potentially promising catalysts for CO2R to CO at an applied potential of −0.7 VSHE while at −0.3 and −1.2 VSHE the reaction is predicted to be hindered by relatively large grand free energy differences between intermediates. We propose a criterion to identify optimum applied potentials for CO2R to CO based on the potential of zero charge (PZC) of the reaction intermediates and the contention that the optimum applied potential for CO2R to CO lies in the range PZC∗CO<𝑉 

   more » « less
5. Synergistic promotion of transition metal ion-exchange in TiO ₂ nanoarray-based monolithic catalysts for the selective catalytic reduction of NO _x with NH ₃

   https://doi.org/10.1039/D2CY00996J  

   Lu, Xingxu; Dang, Yanliu; Li, Meilin; Zhu, Chunxiang; Liu, Fangyuan; Tang, Wenxiang; Weng, Junfei; Ruan, Mingyue; Suib, Steven L.; Gao, Pu-Xian (July 2022, Catalysis Science & Technology)

   TiO 2 supported catalysts have been widely studied for the selective catalytic reduction (SCR) of NO x ; however, comprehensive understanding of synergistic interactions in multi-component SCR catalysts is still lacking. Herein, transition metal elements (V, Cr, Mn, Fe, Co, Ni, Cu, La, and Ce) were loaded onto TiO 2 nanoarrays via ion-exchange using protonated titanate precursors. Amongst these catalysts, Mn-doped catalysts outperform the others with satisfactory NO conversion and N 2 selectivity. Cu co-doping into the Mn-based catalysts promotes their low-temperature activity by improving reducibility, enhancing surface Mn 4+ species and chemisorbed labile oxygen, and elevating the adsorption capacity of NH 3 and NO x species. While Ce co-doping with Mn prohibits the surface adsorption and formation of NH 3 and NO x derived species, it boosts the N 2 selectivity at high temperatures. By combining Cu and Ce as doping elements in the Mn-based catalysts, both the low-temperature activity and the high-temperature N 2 selectivity are enhanced, and the Langmuir–Hinshelwood reaction mechanism was proved to dominate in the trimetallic Cu–Ce–5Mn/TiO 2 catalysts due to the low energy barrier. 

   more » « less