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Electrocatalytic water splitting has been identified as a potential candidate for producing clean hydrogen energy with zero carbon emission. However, the sluggish kinetics of oxygen evolution reaction on the anode side of the water‐splitting device significantly hinders its practical applications. Generally, the efficiency of oxygen evolution processes depends greatly on the availability of cost‐effective catalysts with high activity and selectivity. In recent years, extensive theoretical and experimental studies have demonstrated that cobalt (Co)‐based nanomaterials, especially low‐dimensional Co‐based nanomaterials with a huge specific surface area and abundant unsaturated active sites, have emerged as versatile electrocatalysts for oxygen evolution reactions, and thus, great progress has been made in the rational design and synthesis of Co‐based nanomaterials for electrocatalytic oxygen evolution reactions. Considering the remarkable progress in this area, in this timely review, we highlight the most recent developments in Co‐based nanomaterials relating to their dimensional control, defect regulation (conductivity), electronic structure regulation, and so forth. Furthermore, a brief conclusion about recent progress achieved in oxygen evolution on Co‐based nanomaterials, as well as an outlook on future research challenges, is given. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Highly dispersed ultrasmall ruthenium nanoparticles with a clean surface are deposited onto graphitic carbon nitride (C3N4‐Ru) through spontaneous redox reaction between the C3N4 sheets and Ru salt without the use of any reductant. The as‐prepared C3N4‐Ru exhibits distinct peroxidase‐like activity. A nanozyme based method is successfully developed for detecting the H2O2 generated in‐situ by the two‐electron oxygen reduction strategy. The C3N4‐Ru nanozyme can realize the detection of H2O2 with a wide linear range and a low detection limit. The testing results are also compared with the conventional modified titration method, and show greater possibility for the practical detection of H2O2 produced via the electrochemical oxygen reduction for its higher selectivity. [ABSTRACT FROM AUTHOR]

Understanding the relationship between composition and activity is essential for the rational design of metal‐nitrogen‐Carbon (M−N−C) electrocatalysts for the oxygen reduction reaction (ORR). Here, a series of Fe‐N co‐doped porous carbon (Fe‐N−C) electrocatalysts are successfully prepared through the pyrolysis of ZIF‐8 doped with different amount of hemin. The catalyst (Fe55‐N−C) exhibits impressive ORR performance with an onset potential (Eonset) of 1.02 V (vs. RHE) and a half‐wave potential (E1/2) of 0.892 V in alkaline media, outperforming commercial Pt/C. Meanwhile, the average kinetic current density (Jk) of Fe55‐N−C at 0.850 V is 17.5 mA cm−2, which is 3.3‐fold higher than that of commercial Pt/C. Besides, it also delivers anti‐methanol poisoning ability and high durability. The high performance stems from the hierarchical porous structure, large specific surface area, and high dispersion of Fe‐Nx active sites in Fe55‐N−C. These findings could inspire new perspectives for rationally designing and synthesizing economical and practical non‐precious‐metal oxygen reduction electrocatalysts. [ABSTRACT FROM AUTHOR]

The preparation of luminescent Cs4PbBr6 perovskite solids with current methods either needs a complex procedure, or needs a variety of ligands, and a combination of good solvents and anti‐solvents. The potential environmental risks are inevitable when they are produced in large scale. Herein, an environmentally friendly route for the mass production of luminescent Cs4PbBr6 perovskite solids using a single solvent under ambient conditions is presented. Gram‐scale Cs4PbBr6 perovskite solids are produced within tens of minutes using a small amount of DMF, specifically, 4 mL DMF solution can produce over 10 g products per batch. Because no ligands and anti‐solvents are utilized in the whole procedures, the ligand‐free Cs4PbBr6 perovskite solids are facilely harvested after the evaporation of solvent. More importantly, the solvent vapor can be recovered and reutilized, which can eliminate the environmental pollution caused by organic solvent. The experimental results revealed that the solvent, reaction time, and PbBr2/CsBr molar ratios are crucial for the formation of Cs4PbBr6 perovskite solids and their luminescent performances. Such Cs4PbBr6 perovskite solids exhibit strong green PL emission, high PL quantum yield and reversible fluorescent response towards heat and light, which enable them to be suitable for applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Here, we successfully synthesized N‐doped carbon nanotubes embedded with nickel‐based nanoparticles on the top (N‐CNTs/E‐NNPs) by directly procedural calcination of melamine and nickel foam at 520 °C, 540 °C and 700 °C in Ar. When applied for oxygen reduction reaction (ORR), the onset potential and half‐wave potential are 0.96 V and 0.86 V in 0.1 M KOH, comparable to that of the commercial 10 wt% Pt/C. Moreover, the hybrids possess higher stability and better methanol tolerance. Additionally, the Tafel slope of N‐CNTs/E‐NNPs is 76 mV dec−1 in 0.1 M KOH, lower than 83 mV dec−1 of the commercial 10 wt% Pt/C, demonstrating a good kinetic process. The remarkable features are mainly ascribed to synergistic enhancement effect from N‐rich doped carbon nanotubes (N‐CNTs) and embedded Ni‐based nanoparticles on the top, promoting mass and electrons transport, enhancing the activity of active sites and making it a promising highly efficient non‐precious metal ORR catalyst. [ABSTRACT FROM AUTHOR]

This study provides a unique method for the rapid deposition of amorphous Co−B nanosheets on Ni foam (Co−B/NF) by alternatively dipping Ni foam into cobalt salt and borohydride solutions. The as‐prepared Co−B/NF can act as a highly efficient electrocatalyst for the oxygen evolution reaction (OER). The catalyst affords a current density of 20 mA cm−2 at 265 mV overpotential during the OER in 1.0 M KOH solution, ranking it among the best reported nonprecious OER electrocatalysts. This strategy for constructing electrocatalysis electrodes prevails over the conventional method of drop‐coating metal boride dispersions on the electrode, having better intrinsic stability and fully exposed active site surfaces. Given the low cost, ease of fabrication, good controllability, and high OER electrocatalytic activity and stability, Co−B/NF has great potential as a high‐performance anode catalyst for water splitting. [ABSTRACT FROM AUTHOR]

A highly efficient and durable electrocatalyst of Pd hydride nanocubes encapsulated within 2D amorphous Ni-B nanosheets is reported. The PdH0.43 nanocubes are first synthesized via a simple N, N-dimethylformamide thermal treatment. The as-synthesized PdH0.43 nanocubes are then encapsulated in 2D amorphous NiB nanosheets by NaBH4 reduction in the presence of nickel species. During the NaBH4 treatment, the PdH0.43 can be further transformed into PdH0.706 due to the presence of endogenous H2. Electrochemical studies demonstrate that the degree of hydride of Pd nanocubes (PdH x) plays an important role in the enhancement of their oxygen reduction reaction (ORR) activity. With increasing x value, both the activity and stability increase significantly. At 0.90 V versus reversible hydrogen electrode, the ORR activity of PdH0.706 @Ni-B reaches 1.05 A mgPd−1, which is nearly five times higher than that of the state-of-the-art Pt catalysts. Accelerated durability tests show that even after 10 000 potential cycles, there is negligible shift in their half-wave potential and no shape and structure change occurs, indicating the incorporation of amorphous 2D Ni-B nanosheets can greatly improve their stability without compromising their activity. The present study illustrates the importance of high degree of hydride and presence of amorphous Ni-B nanosheets on the enhancement of ORR activity for Pd-based electrocatalyst. [ABSTRACT FROM AUTHOR]

The C3 selectivity of carbon-supported Au nanoparticles for glycerol electro-oxidation was significantly enhanced by the interaction of Au with electro-deposited Cu species. Notably, the C3 selectivity of supported Au nanoparticles doubled after 90 min of Cu electro-deposition at +0.015 V. This result was obtained if glycerol electro-oxidation was performed at +0.1 V for 2 h. The most selective catalysts contained an Au+ species that was generated by an interaction between Au and electro-deposited Cu2O. The presence of Au+ increased the selectivity to glycerate and tartronate and suppressed C−C bond cleavage to glycolate and formate simultaneously. [ABSTRACT FROM AUTHOR]

By controlling the surface structure and composition at the atomic level, the catalytic properties of bimetallic alloy catalysts can be precisely and effectively tuned, and their activity and durability can be enhanced. Here, a class of highly active and durable PdAg bimetallic alloy nano-electrocatalysts is demonstrated by tuning the surface composition through a simple electrochemical treatment process in acid medium. Transmission electron microscopy, X-ray photoelectron spectroscopy, and cyclic voltammogram measurements clearly show the well-defined core-shell structure that consists of a PdAg alloy core and a few atomic layers of Pd as the shell (PdAg@Pd). Compared to pure Pd and Ag catalysts, the prepared PdAg@Pd/C exhibits enhanced electrocatalytic activity and durability for the oxygen reduction reaction in alkaline media. According to the theoretical and experimental results, the enhanced electrocatalytic activity can be attributed to the synergistic effects between the Pd and the Ag, while the durability is ascribed to the unique alloy core-ultrathin-Pd-shell structure of the PdAg@Pd/C catalyst. This study not only proposes a simple and straightforward approach for preparing highly monodisperse PdAg alloy nanoparticles and designing advanced electrocatalysts for fuel cells, but also demonstrates the crucial effect of electrochemical treatment on the electrocatalytic properties of catalysts. [ABSTRACT FROM AUTHOR]

Due to the high costs, slow reaction kinetics, and methanol poisoning of platinum-based cathode catalysts, designing and exploring non-Pt or low-Pt cathode electrocatalysts with a low cost, high catalytic performance, and high methanol-tolerance are crucial for the commercialization of fuel cells. Here, a facile method to fabricate a system of PdAg nanorings supported by graphene nanosheets is demonstrated; the fabrication is based on the galvanic displacement reaction between pre-synthesized Ag nanoparticles and palladium ions. X-ray diffraction and high-resolution transmission electron microscopy show that the synthesized PdAg nanocrystals exhibit a ring-shaped hollow structure with an average size of 27.49 nm and a wall thickness of 5.5 nm. Compared to the commercial Pd-C catalyst, the PdAg nanorings exhibit superior properties as a cathode electrocatalyst for oxygen reduction. Based on structural and electrochemical studies, these advantageous properties include efficient usage of noble metals and a high surface area because of the effective utilization of both the exterior and interior surfaces, high electrocatalytic performance for oxygen reduction from the synergistic effect of the alloyed PdAg crystalline phase, and most importantly, excellent tolerance of methanol crossover at high concentrations. It is anticipated that this synthesis of graphene-based PdAg nanorings will open up a new avenue for designing advanced electrocatalysts that are low in cost and that exhibit high catalytic performance for alkaline fuel cells. [ABSTRACT FROM AUTHOR]

Keywords: Fe-N co-doped carbon; tunable composition; high dispersion; oxygen reduction; fuel cells EN Fe-N co-doped carbon tunable composition high dispersion oxygen reduction fuel cells 992 992 1 03/29/21 20210312 NES 210312 B The Cover Feature b illustrates a novel iron-nitrogen co-doped carbon (Fe-N-C) with a hierarchical porous structure, large specific surface area, and high dispersion of Fe-N SB x sb active sites, which can serve as a high-performance electrocatalyst for the oxygen reduction reaction. Cover Feature: Iron-Nitrogen Co-doped Carbon with a Tunable Composition as Efficient Electrocatalysts for Oxygen Reduction (ChemElectroChem 6/2021) Fe-N co-doped carbon, tunable composition, high dispersion, oxygen reduction, fuel cells. [Extracted from the article]

Direct electrochemical production of hydrogen peroxide (H2O2) through two‐electron oxygen electrochemistry, for example, the oxygen reduction in fuel cells or water oxidation in water electrolyzers, could provide an attractive alternative to locally produce this chemical on demand. The efficiency of these processes depends greatly on the availability of cost‐effective catalysts with high selectivity, activity, and stability. In recent years, various novel nanostructured materials have been reported to selectively produce H2O2. Through combined experimental and theoretical approaches, underlying mechanisms in the electrochemical synthesis of H2O2 via oxygen electrochemistry have been unveiled. Considering the remarkable progress in this area, the authors summarize recent developments regarding the direct production of H2O2 through two‐electron electrochemical oxygen reactions. The fundamental aspects of electrochemical oxygen reactions are first introduced. Various types of catalysts that can effectively produce H2O2 via two‐electron oxygen electrochemistry are then presented. In parallel, the unique structure‐, component‐, and composition‐dependent electrochemical performance together with the underlying catalytic mechanisms are discussed. Finally, a brief conclusion about the recent progress achieved in electrochemical generation of H2O2 and an outlook on future research challenges are given. Direct electrochemical production of hydrogen peroxide (H2O2) through two‐electron oxygen reduction and water oxidation is summarized. The structure, components, and composition of the electrocatalysts show strong correlation with their selectivity, activity, and durability. This review also provides some guidelines for rational design of highly efficient electrocatalysts toward electrochemical H2O2 generation on demand. [ABSTRACT FROM AUTHOR]

Review: 119 refs. [ABSTRACT FROM AUTHOR]

On page 1289, Wei Chen and co‐workers report a method to fabricate graphene‐supported PdAg nanorings. As a potential fuel cell electrocatalyst, the hybrid nanomaterial exhibits excellent catalytic performance for oxygen reduction with the clean product of water. The unique nanostructure of the material with large active surface area, low noble metal loading, and high methanol tolerance is highlighted. [ABSTRACT FROM AUTHOR]

Review: noble and coinage metals; 318 refs. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Highly dispersed ultrasmall ruthenium nanoparticles with a clean surface are deposited onto graphitic carbon nitride (C3N4‐Ru) through spontaneous redox reaction between the C3N4 sheets and Ru salt without the use of any reductant. The as‐prepared C3N4‐Ru exhibits distinct peroxidase‐like activity. A nanozyme based method is successfully developed for detecting the H2O2 generated in‐situ by the two‐electron oxygen reduction strategy. The C3N4‐Ru nanozyme can realize the detection of H2O2 with a wide linear range and a low detection limit. The testing results are also compared with the conventional modified titration method, and show greater possibility for the practical detection of H2O2 produced via the electrochemical oxygen reduction for its higher selectivity. [ABSTRACT FROM AUTHOR]