Huicong Xia

Abstract Developing active, robust, and nonprecious electrocatalysts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is highly crucial and challenging. In this work, a facile strategy is developed for scalable fabrication of dicobalt phosphide (Co 2 P)–cobalt nitride (CoN) core–shell nanoparticles with double active sites encapsulated in nitrogen‐doped carbon nanotubes (Co 2 P/CoN‐in‐NCNTs) by straight forward pyrolysis method. Both density functional theory calculation and experimental results reveal that pyrrole nitrogen coupled with Co 2 P is the most active one for HER, while Co–N–C active sites existing on the interfaces between CoN and N‐doped carbon shells are responsible for the ORR and OER activity in this catalyst. Furthermore, liquid‐state and all‐solid‐state Zn–air batteries are equipped. Co 2 P/CoN‐in‐NCNTs show high power density as high as 194.6 mW cm −2 , high gravimetric energy density of 844.5 W h kg −1 , very low charge–discharge polarization, and excellent reversibility of 96 h at 5 mA cm −2 in liquid system. Moreover, the Co 2 P/CoN‐in‐NCNTs profiles confirm excellent activity for water splitting.

molecule in side-on mode and accelerates ORR kinetics.

Abstract During the preparation of atomically dispersed Fe–N–C catalysts, it is difficult to avoid the formation of iron‐carbide‐containing iron clusters (“Fe x C/Fe”), along with the desired carbon matrix containing dispersed FeN x sites. As a result, an uncertain amount of the oxygen reduction reaction (ORR) occurs, making it difficult to maximize the catalytic efficiency. Herein, sulfuration is used to boost the activity of Fe x C/Fe, forming an improved system, “FeNC–S–Fe x C/Fe”, for catalysis involving oxygen. Various spectroscopic techniques are used to define the composition of the active sites, which include Fe–S bonds at the interface of the now‐S‐doped carbon matrix and the Fe x C/Fe clusters. In addition to outstanding activity in basic media, FeNC–S–Fe x C/Fe exhibits improved ORR activity and durability in acidic media; its half‐wave potential of 0.821 V outperforms the commercial Pt/C catalyst (20%), and its activity does not decay even after 10 000 cycles. Interestingly, the catalytic activity for the oxygen evolution reaction (OER) simultaneously improves. Thus, FeNC–S–Fe x C/Fe can be used as a high‐performance bifunctional catalyst in Zn–air batteries. Theoretical calculations and control experiments show that the original FeN x active centers are enhanced by the Fe x C/Fe clusters and the Fe–S and C–S–C bonds.

Metal–organic frameworks (MOFs) are of great interest as potential electrochemically active materials. However, few studies have been conducted into understanding whether control of the shape and components of MOFs can optimize their electrochemical performances due to the rational realization of their shapes. Component control of MOFs remains a significant challenge. Herein, we demonstrate a solvothermal method to realize nanostructure engineering of 2D nanoflake MOFs. The hollow structures with Ni/Co- and Ni-MOF (denoted as Ni/Co-MOF nanoflakes and Ni-MOF nanoflakes) were assembled for their electrochemical performance optimizations in supercapacitors and in the oxygen reduction reaction (ORR). As a result, the Ni/Co-MOF nanoflakes exhibited remarkably enhanced performance with a specific capacitance of 530.4 F g−1 at 0.5 A g−1 in 1 M LiOH aqueous solution, much higher than that of Ni-MOF (306.8 F g−1) and ZIF-67 (168.3 F g−1), a good rate capability, and a robust cycling performance with no capacity fading after 2000 cycles. Ni/Co-MOF nanoflakes also showed improved electrocatalytic performance for the ORR compared to Ni-MOF and ZIF-67. The present work highlights the significant role of tuning 2D nanoflake ensembles of Ni/Co-MOF in accelerating electron and charge transportation for optimizing energy storage and conversion devices.

) reduction (ECR) has become one of the main methods to close the broken carbon cycle and temporarily store renewable energy, but there are still some problems such as poor stability, low activity, and selectivity. While the most promising strategy to improve ECR activity is to develop electrocatalysts with low cost, high activity, and long-term stability. Recently, defective carbon-based nanomaterials have attracted extensive attention due to the unbalanced electron distribution and electronic structural distortion caused by the defects on the carbon materials. Here, the present review mainly summarizes the latest research progress of the construction of the diverse types of defects (intrinsic carbon defects, heteroatom doping defects, metal atomic sites, and edges detects) for carbon materials in ECR, and unveil the structure-activity relationship and its catalytic mechanism. The current challenges and opportunities faced by high-performance carbon materials in ECR are discussed, as well as possible future solutions. It can be believed that this review can provide some inspiration for the future of development of high-performance ECR catalysts.