An official website of the United States government
Abstract Developing eco‐friendly electrochemical devices for electrosynthesis, fuel cells (FCs), and metal‐air batteries (MABs) requires precisely designing the electronic pathway in the oxygen reduction reaction (ORR) process. Understanding the principle of developing low‐cost, highly active, and stable catalysts helps to reduce the usage of noble metals in ORR. Atomically dispersed metal catalysts (ADMCs) emerge as promising alternatives to replace commercial noble metals due to their high utilization of active metal atoms, high intrinsic activity, and controllable coordination environments. In this review, the research tendency and reaction mechanisms in ORR are first summarized. The basic principles concerning the geometric size and chemical coordination of two‐electron ORR (2e−ORR) catalysts were then discussed, aiming to outline the evolution of material design from 2e−ORR to four‐electron ORR (4e−ORR). Subsequently, recent advances in ADMCs primarily investigated for the 4e−ORR are well‐documented. These advances encompass studies on M−N−C coordination, light heteroatom doping, dual‐metal atoms‐based coordination, and interaction between nanoparticle (NPs)/nanoclusters (NCs) and atomically dispersed metals (ADMs). Finally, the setups for 2/4e−ORR applications, key challenges, and opportunities in the future design of ADMCs for the ORR are highlighted.
more »
« less
Cobalt‐Catalyzed Allylic Alkylation at sp 3 ‐Carbon Centers
Abstract The rising demand and financial costs of noble transition metal catalysts have emphasized the need for sustainable catalytic approaches. Over the past few years, base‐metal catalysts have emerged as ideal candidates to replace their noble‐metal counterparts because of their abundance and easiness of handling. Despite the significant advancements achieved with precious transition metals, earth‐abundant cobalt catalysts have emerged as efficient alternatives for allylic substitution reactions. In this review, allylic alkylations at sp3‐carbon centers mediated by cobalt will be discussed, with a special focus on the mechanistic features, scope, and limitations.
more »
« less
- Award ID(s):
- 2247708
- PAR ID:
- 10642372
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 30
- Issue:
- 47
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Noble‐metal nanostructures have emerged as a category of efficient and versatile peroxidase mimics in recent years. Enhancing their peroxidase‐like activities is essential to the realization of certain applications. In this review, we focus on how to engineer noble‐metal nanostructures with enhanced peroxidase‐like activities. The article is organized by introducing the impacts of surface capping ligands, particle size, shape, elemental composition, and internal structure as key parameters for the peroxidase‐like activity of noble‐metal nanostructures. Emphasis is given to the controlled synthesis of nanostructures and their peroxidase‐like catalytic efficiencies. At the end, we provide a perspective on future developments in the research relevant to peroxidase mimics of noble metals.more » « less
-
Abstract High‐efficiency and low‐cost catalysts for oxygen evolution reaction (OER) are critical for electrochemical water splitting to generate hydrogen, which is a clean fuel for sustainable energy conversion and storage. Among the emerging OER catalysts, transition metal dichalcogenides have exhibited superior activity compared to commercial standards such as RuO2, but inferior stability due to uncontrolled restructuring with OER. In this study, we create bimetallic sulfide catalysts by adapting the atomic ratio of Ni and Co in CoxNi1‐xSyelectrocatalysts to investigate the intricate restructuring processes. Surface‐sensitive X‐ray photoelectron spectroscopy and bulk‐sensitive X‐ray absorption spectroscopy confirmed the favorable restructuring of transition metal sulfide material following OER processes. Our results indicate that a small amount of Ni substitution can reshape the Co local electronic structure, which regulates the restructuring process to optimize the balance between OER activity and stability. This work represents a significant advancement in the development of efficient and noble metal‐free OER electrocatalysts through a doping‐regulated restructuring approach.more » « less
-
Abstract Reduction of the cobalt(II) chloride complex, Ph2B(tBuIm)2Co(THF)Cl (1) in the presence oftBuN≡C affords the diamagnetic, square planar cobalt(I) complex Ph2B(tBuIm)2Co(C≡NtBu)2(2). This is a rare example of a 16‐electron cobalt(I) complex that is structurally related to square planar noble metal complexes. Accordingly, the electronic structure of2, as calculated by DFT, reveals that the HOMO is largely dz2in character. Complex2is readily oxidized to its cobalt(II) congener [Ph2B(tBuIm)2Co(C=NtBu)2]BPh4(3‐BPh4), whose EPR spectral parameters are characteristic of low‐spin d7with an unpaired electron in an orbital of dz2parentage. This is also consistent with the results of DFT calculations. Despite its 16‐electron configuration and the dz2parentage of the HOMO, the only tractable reactions of2involve one electron oxidation to afford3.more » « less
-
Abstract In recent years, there has been a concerted drive to develop methods that are greener and more sustainable. Being an earth‐abundant transition metal, cobalt offers an attractive substitute for commonly employed precious metal catalysts, though reactions engaging cobalt are still less developed. Herein, we report a method to achieve the decarboxylative allylation of nitrophenyl alkanes, nitroalkanes, and ketones employing cobalt. The reaction allows for the formation of various substituted allylated products in moderate‐excellent yields with a broad scope. Additionally, the synthetic potential of the methodology is demonstrated by the transformation of products into versatile heterocyclic motifs. Mechanistic studies revealed an in situ activation of the Co(II)/dppBz precatalyst by the carboxylate salt to generate a Co(I)‐species, which is presumed to be the active catalyst.more » « less
