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Replacing expensive platinum oxygen reduction reaction (ORR) catalysts with atomically dispersed single-atom catalysts is an effective way to improve the energy conversion efficiency of fuel cells. Herein, a series of single-atom catalysts, TM-N2O2Cx (TM=Sc-Zn) with TM-N2O2 active units, were designed, and their catalytic performance for electrocatalytic O2 reduction was investigated based on density functional theory. The results show that TM-N2O2Cx exhibits excellent catalytic activity and stability in acidic media. The eight catalysts (TM=Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) are all 4e− reaction paths, among which Sc-N2O2Cx, Ti-N2O2Cx, and V-N2O2Cx follow dissociative mechanisms and the rest are consistent with associative mechanisms. In particular, Co-N2O2Cx and Ni-N2O2Cx enable a smooth reduction in O2 at small overpotentials (0.44 V and 0.49 V, respectively). Furthermore, a linear relationship between the adsorption free energies of the ORR oxygen-containing intermediates was evident, leading to the development of a volcano plot for the purpose of screening exceptional catalysts for ORR. This research will offer a novel strategy for the design and fabrication of exceptionally efficient non-precious metal catalysts on an atomic scale. [ABSTRACT FROM AUTHOR]

The surface grafting of electro‐negative cyano groups on polymer carbon nitrides (PCNs) is an effective way to tail their electronic structure. Despite the significant progress in the synthesis of cyano group‐enriched PCN, developing a simple and efficient method remains challenging. Here, a facile strategy was developed for fabricating surface cyano‐rich PCN (PCN‐DM) with a porous structure via chemical vapor modification using diaminomaleonitrile. The cyano groups of diaminomaleonitrile substituted the amino groups on PCN surface via a deamination. The hydrogen production rate of the PCN‐DM was approximately 17 times higher than that of pristine PCN. This significant increase in photocatalytic performance could be assigned to the fusion of cyano groups in the surface of PCN, forming new gap states that broadened the visible‐light harvesting and accelerated charge separation for photoredox reactions. This study unveils a promising approach for incorporating functional units in the design of novel photocatalysts for efficient hydrogen production. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (AZIBs) based on high-safety zinc metal anodes have advantages of low cost and high theoretical capacity and are considered as a promising large-scale energy storage system. Their practical application, however, is hampered by slow transport kinetics, low energy density, and poor cycling performance. In this work, we design and successfully synthesize ultrastable lattice water-rich VO2·xH2O materials by considering the fact that abundant crystallized water can act as "water lubrication", and a charge shielding medium to weaken the electrostatic effect. As a result, VO2·xH2O as a cathode for AZIBs can provide a specific capacity of 376 mA h g−1 after 200 cycles at 1 A g−1 and no apparent capacity decay after 8000 cycles at 15 A g−1. The excellent zinc storage performance can be ascribed to the efficient kinetics and abundant reaction sites of the VO2·xH2O electrode. A series of in situ and ex situ characterizations indicate that it is the H+/Zn2+ co-intercalation mechanism to store zinc in the VO2·xH2O electrode. In short, the abundant crystallized water vanadium-based materials may be excellent candidates for advanced cathode materials of AZIBs. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) with porous structures derived from transition metal oxides have been shown to be effective at storing lithium and converting it. During the course of this research, N-doped porous carbon-covered Co3O4 nanoparticle composites (Co3O4/NC-2) were manufactured by employing a novel cobalt-based MOF as a sacrificial template. The N-doped porous carbon coating improves the electrical conductivity while also reducing the path that Li+ takes to diffuse through the material. During this time, the composite's volume change that occurs during galvanostatic discharge/charge cycles is effectively buffered, and the cycling stability of the composite is improved. As a result, Co3O4/NC-2 has excellent lithium storage properties. After 100 cycles at 0.1 A g−1, the reversible capacity of Co3O4/NC-2 is 884.2 mAh g−1. Furthermore, Co3O4/NC-2 has an excellent rate capability. The reversible specific capacity can be recovered to 1124.6 mAh g−1 by increasing the current density from 0.1 A g−1 to 5 A g−1 and back to 0.1 A g−1. We design and synthesize a novel MOF as a sacrificial template in this paper to provide a simple method for fabricating highly electrochemical electrode materials. The N-doped porous carbon-coated Co3O4 nanoparticle composite (Co3O4/NC-2) is obtained by annealing treatment of a novel precursor Co-MOF, and exhibited excellent electrochemical performance as anode materials for Li-ion batteries. [ABSTRACT FROM AUTHOR]

Designing highly active multifunctional catalysts to meet the demands for fuel cells, metal–air batteries, and water-splitting devices is a top priority. Here, an efficient and novel trifunctional electrocatalyst (Fe2P/Co@NPC) with Fe2P and Co nanoparticles embedded in porous carbon has been developed by facile one-pot pyrolysis. The synergistic effect of Fe2P and Co nanoparticles furnishes Fe2P/Co@NPC with excellent catalytic performance for oxygen reduction reaction (ORR, E1/2 = 0.876 V), oxygen evolution reaction (OER, η10 = 331 mV), and hydrogen evolution reaction (HER, η10 = 235 mV). Significantly, using Fe2P/Co@NPC catalyst as the cathode, the assembled anion exchange membrane fuel cell delivers a peak power density of 1.25 W cm−2. Moreover, the assembled rechargeable Zn–air battery, using Fe2P/Co@NPC as a bifunctional oxygen catalyst, exhibits a maximum power density of 233.56 mW cm−2 and impressive cycle performance. Using Fe2P/Co@NPC as a bifunctional HER and OER catalyst, the overall water electrolyzer also achieves a low voltage of 1.73 V to deliver 10 mA cm−2. This work represents a protocol for the preparation of high efficient trifunctional electrocatalysts using cheaper heteroatom-containing metal–organic small molecules as a precursor for electrochemical energy devices. [ABSTRACT FROM AUTHOR]