This review presents recent developments in the design and synthesis of Pt-based catalysts with high atom utilization efficiency and their enhanced catalytic performance in electrochemical catalytic reactions.

nanoparticles (NPs) catalysts, SACs display unique features like their unsaturatedcoordination configuration, quantum size effect, and strong atom-support interaction, which induce the single-atom sites with excellent activity and stability in electrocatalysis. [1b,2] In 2011, Zhang and co-workers employed a coprecipitation method to prepare Pt SACs supported on iron oxide which demonstrated high activity and stability for CO oxidation. [3] Sun and co-workers reported the fabrication of Pt SACs on graphene by atomic layer deposition, and the as-prepared Pt SACs showed 10 times higher activity for methanol oxidation and superior CO tolerance compared to the benchmark Pt/C catalyst. [4] According to this research, it can be seen that "single atom catalysts" developed rapidly and have become a hot research topic in heterogeneous electrocatalysis. 1.1. Identification and Features of SACs SACs have isolated metal atoms that are anchored on a specific support and can behave as active centers for heterogeneous catalysis. The concept of single-atom catalysts can be traced back to the pioneering research reported by Zhang and co-workers in 2011. In their work, well-dispersed Pt single atoms were successfully prepared on the FeOx support, which opens the avenue of "single atom catalysts." The active single-atom sites generally consist of metal atoms and neighboring atoms from support materials. In addition, ion-exchanged metal atoms located on a porous support, as well as organometallic complexes anchored to the substrate, in principle, could also be viewed as SACs. The unique features of single atoms are significantly different from NPs, which endow SACs with exceptional catalytic activity, stability and selectivity. i) Decreasing the size of metal particles down to single atoms results in the maximum atom-utilization efficiency and metal dispersion. Owing to the low-coordination environment property and fully exposed active sites, SACs are capable to exhibit remarkable electrocatalytic activity toward diverse reactions. [5] ii) Single metal atoms can coordinate with support materials via strong interaction or charge transfer, which ensure the atomic dispersion and enhanced stability of SACs. [6] iii) The uniform active sites and geometric configuration of SACs enable similar electronic and spatial interactions with reactant molecules, thereby achieving Electrocatalysis plays a critical role in clean energy conversion, enabling great improvement for future sustainable technologies. Single atom catalysts (SACs) derived from metal-organic framework (MOF) are emerging extraordinary materials in electrochemical catalytic applications. Covering the merits of unique electronic structure, low-coordination environment, quantum size effect, and metal-support interaction, SACs promise enhanced electrocatalytic activity, stability, and selectivity in the field of clean energy conversion. In this article, MOF synthesis routes to afford well-dispersed SACs along with the respective synthesis mechanism are systematically reviewed first...

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Sulfide-based solid-state electrolytes (SSEs) are considered a key part in the realization of high-performance all solid-state lithium-ion batteries (ASSLIBs). However, the incompatibility between conductive additives and sulfide-based SSEs in the cathode composite challenges the stable delivery of high-rate capability. Herein, a poly­(3,4-ethylenedioxythiophene) (PEDOT) modification is designed as a semiconductive additive for cathode composites (cathode/SSE/carbon) to realize the high performance. The modified ASSLIB demonstrates a competitive rate capacity of over 100 mAh g–1 at 1C, which is 10 times greater than that of the bare cathode. Detailed surface chemical and structural evolutions at the cathodic interface indicate the PEDOT modification not only significantly suppresses the side reactions but also realizes effective electron transfer at the cathode/SSE/carbon three-phase interface. Introducing a controllable semiconductive additive for the cathode composites in this study offers a promising design to realize the high-rate performance and overcome long-term challenges in the application of conductive additives in sulfide-based ASSLIBs.

Configuring metal single‐atom catalysts (SACs) with high electrocatalytic activity and stability is one efficient strategy in achieving the cost‐competitive catalyst for fuel cells’ applications. Herein, the atomic layer deposition (ALD) strategy for synthesis of Pt SACs on the metal–organic framework (MOF)‐derived N‐doped carbon (NC) is proposed. Through adjusting the ALD exposure time of the Pt precursor, the size‐controlled Pt catalysts, from Pt single atoms to subclusters and nanoparticles, are prepared on MOF‐NC support. X‐ray absorption fine structure spectra determine the increased electron vacancy in Pt SACs and indicate the Pt–N coordination in the as‐prepared Pt SACs. Benefiting from the low‐coordination environment and anchoring interaction between Pt atoms and nitrogen‐doping sites from MOF‐NC support, the Pt SACs deliver an enhanced activity and stability with 6.5 times higher mass activity than that of Pt nanoparticle catalysts in boosting the oxygen reduction reaction (ORR). Density functional theory calculations indicate that Pt single atoms prefer to be anchored by the pyridinic N‐doped carbon sites. Importantly, it is revealed that the electronic structure of Pt SAs can be adjusted by adsorption of hydroxyl and oxygen, which greatly lowers free energy change for the rate‐determining step and enhances the activity of Pt SACs toward the ORR.

Single-atom catalysts (SACs) have been applied in many fields due to their superior catalytic performance. Because of the unique properties of the single-atom-site, using the single atoms as catalysts to synthesize SACs is promising. In this work, we have successfully achieved Co1 SAC using Pt1 atoms as catalysts. More importantly, this synthesis strategy can be extended to achieve Fe and Ni SACs as well. X-ray absorption spectroscopy (XAS) results demonstrate that the achieved Fe, Co, and Ni SACs are in a M1-pyrrolic N4 (M= Fe, Co, and Ni) structure. Density functional theory (DFT) studies show that the Co(Cp)2 dissociation is enhanced by Pt1 atoms, thus leading to the formation of Co1 atoms instead of nanoparticles. These SACs are also evaluated under hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the nature of active sites under HER are unveiled by the operando XAS studies. These new findings extend the application fields of SACs to catalytic fabrication methodology, which is promising for the rational design of advanced SACs.

All-solid-state metal batteries (ASSMBs) are attracting much attention due to their cost effectiveness, enhanced safety, room-temperature performance and high theoretical specific capacity. However, the alkali metal anodes (such as Li and Na) are active enough to react with most solid-state electrolytes (SSEs), leading to detrimental reactions at the metal-SSE interface. In this work, a molecular layer deposition (MLD) alucone film is employed to stabilize the active Na anode/electrolyte interface in the ASSMBs, limiting the decomposition of the sulfide-based electrolytes (Na 3 SbS 4 and Na 3 PS 4 ) and Na dendrite growth. Such a strategy effectively improves the room-temperature full battery performance as well as cycling stability for over 475 h in Na-Na symmetric cells. The modified interface is further characterized by X-ray photoelectron spectroscopy (XPS) depth profiling, which provides spatially resolved evidence of the synergistic effect between the dendrite-suppressed sodiated alucone and the insulating unsodiated alucone. The coupled layers reinforce the protection of the Na metal/electrolyte interface. Therefore, alucone is identified as an effective and bifunctional coating material for the enhancement of the metal/electrolyte interfacial stability, paving the way for rapid development and wide application of high-energy ASSMBs.

Single-atom catalysts (SACs) have attracted significant attention due to their superior catalytic activity and selectivity. However, the nature of active sites of SACs under realistic reaction conditions is ambiguous. In this work, high loading Pt single atoms on graphitic carbon nitride (g-C 3 N 4)-derived N-doped carbon nanosheets (Pt 1 /NCNS) is achieved through atomic layer deposition. Operando X-ray absorption spectroscopy (XAS) is performed on Pt single atoms and nanoparticles (NPs) in both the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The operando results indicate that the total unoccupied density of states of Pt 5d orbitals of Pt 1 atoms is higher than that of Pt NPs under HER condition, and that a stable Pt oxide is formed during ORR on Pt 1 /NCNS, which may suppress the adsorption and activation of O 2. This work unveils the nature of Pt single atoms under realistic HER and ORR conditions, providing a deeper understanding for designing advanced SACs.