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1. 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)

   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.

    

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2. Dual‐Atom Catalysts for Electrochemical Energy Technologies

   https://doi.org/10.1002/ente.202201456  

   Cui, Tianchen ; Liu, Qiming ; Chen, Shaowei ( February 2023 , Energy Technology)

   Rational design and engineering of high‐performance, low‐cost electrocatalysts represents a critical first step in the development of sustainable energy technologies. While single‐atom catalysts (SACs) have emerged as viable candidates, recent research has shown that the structure and activity can be further manipulated and enhanced by the incorporation of a second metal center in the close proximity, forming a binuclear configuration. Such dual‐atom catalysts (DACs) are recognized as feasible choices to break the limitations of SACs due to the synergetic effects between the bimetallic atoms and their special structures. Herein, the recent advances of DAC electrocatalysis for a range of important reactions, focusing on their synthesis, characterization, and performance, are summarized. The review is concluded with a perspective highlighting the challenges and future research directions.

    

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3. Carbon‐Rich Nonprecious Metal Single Atom Electrocatalysts for CO 2 Reduction and Hydrogen Evolution

   https://doi.org/10.1002/smtd.201900210  

   Wang, Tingting ; Zhao, Qidong ; Fu, Yuanyuan ; Lei, Chaojun ; Yang, Bin ; Li, Zhongjian ; Lei, Lecheng ; Wu, Gang ; Hou, Yang ( May 2019 , Small Methods)

   Single atom catalysts (SACs) are considered as the emerging catalysts for boosting electricity‐driven CO₂reduction reaction (CRR) and hydrogen evolution reaction (HER). To replace the rare and expensive noble metal electrocatalysts, developing nonprecious metal SACs (NPMSACs) with superior electrocatalytic activity and stability is of paramount importance for achieving high efficiency in CRR and HER. Herein, a brief overview of recent achievements in the carbon‐rich NPMSACs for both CRR and HER is provided. The synthesis strategies and corresponding electrocatalytic performances of various carbon‐rich NPMSACs are discussed in the order of various metals (Ni, Co, Fe, Zn, and Sn for CRR, as well as Ni, Co, Fe, Mo, and W for HER), with a special attention paid to understand the structure–activity relationships. Finally, the remaining challenges and future perspectives for enhancing CRR and HER performance of NPMSACs are outlined.

    

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4. Pt 1 –O 4 as active sites boosting CO oxidation via a non-classical Mars–van Krevelen mechanism

   https://doi.org/10.1039/D1CY00115A  

   Lou, Yang ; Zheng, Yongping ; Guo, Wenyi ; Liu, Jingyue ( May 2021 , Catalysis Science & Technology)

   null (Ed.)

   Single-atom catalysts (SACs) exhibit excellent performance for various catalytic reactions but it is still challenging to have adequate total activity for practical applications. Here we report the high-valence, square planar Pt 1 –O 4 as an active site that enables significantly to increase the total activity of the Pt 1 /Fe 2 O 3 SAC with a Pt loading of only ∼30 ppm, which is similar to that of a 1.0 wt% nano-Pt/Fe 2 O 3 , for CO oxidation at 350 °C. Density functional theory calculations reveal that Pt 1 –O 4 catalyzes CO oxidation through a non-classical Mars–van Krevelen mechanism. The adsorbed O 2 on Pt 1 atoms activates the coordination oxygen in the Pt 1 –O 4 configuration, and then a barrierless O 2 dissociation occurs on the Pt 1 –Fe 2 triangle to replenish the consumed coordination oxygen by the cooperative action of Pt 5d and Fe 3d electrons. This work provides a new fundamental understanding of oxidation catalysis on stable and active SACs, providing guidance for rationally designing future heterogeneous catalysts. 

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5. Enhancing the activity of Pd ensembles on graphene by manipulating coordination environment

   https://doi.org/10.1073/pnas.2216879120  

   Huang, Dahong ; Rigby, Kali ; Chen, Weirui ; Wu, Xuanhao ; Niu, Junfeng ; Stavitski, Eli ; Kim, Jae-Hong ( February 2023 , Proceedings of the National Academy of Sciences)

   Atomic dispersion of metal catalysts on a substrate accounts for the increased atomic efficiency of single-atom catalysts (SACs) in various catalytic schemes compared to the nanoparticle counterparts. However, lacking neighboring metal sites has been shown to deteriorate the catalytic performance of SACs in a few industrially important reactions, such as dehalogenation, CO oxidation, and hydrogenation. Metal ensemble catalysts (M n ), an extended concept to SACs, have emerged as a promising alternative to overcome such limitation. Inspired by the fact that the performance of fully isolated SACs can be enhanced by tailoring their coordination environment (CE), we here evaluate whether the CE of M n can also be manipulated in order to enhance their catalytic activity. We synthesized a set of Pd ensembles (Pd n ) on doped graphene supports (Pd n /X-graphene where X = O, S, B, and N). We found that introducing S and N onto oxidized graphene modifies the first shell of Pd n converting Pd–O to Pd–S and Pd–N, respectively. We further found that the B dopant significantly affected the electronic structure of Pd n by serving as an electron donor in the second shell. We examined the performance of Pd n /X-graphene toward selective reductive catalysis, such as bromate reduction, brominated organic hydrogenation, and aqueous-phase CO 2 reduction. We observed that Pd n /N-graphene exhibited superior performance by lowering the activation energy of the rate-limiting step, i.e., H 2 dissociation into atomic hydrogen. The results collectively suggest controlling the CE of SACs in an ensemble configuration is a viable strategy to optimize and enhance their catalytic performance. 

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