The three-dimensional (3D) distribution of individual atoms on the surface of catalyst nanoparticles plays a vital role in their activity and stability. Optimising the performance of electrocatalysts requires atomic-scale information, but it is difficult to obtain. Here, we use atom probe tomography to elucidate the 3D structure of 10 nm sized Co2FeO4 and CoFe2O4 nanoparticles during oxygen evolution reaction (OER). We reveal nanoscale spinodal decomposition in pristine Co2FeO4. The interfaces of Co-rich and Fe-rich nanodomains of Co2FeO4 become trapping sites for hydroxyl groups, contributing to a higher OER activity compared to that of CoFe2O4. However, the activity of Co2FeO4 drops considerably due to concurrent irreversible transformation towards CoIVO2 and pronounced Fe dissolution. In contrast, there is negligible elemental redistribution for CoFe2O4 after OER, except for surface structural transformation towards (FeIII, CoIII)2O3. Overall, our study provides a unique 3D compositional distribution of mixed Co-Fe spinel oxides, which gives atomic-scale insights into active sites and the deactivation of electrocatalysts during OER.

(1 of 11)with structural merits and unique physicochemical properties inherited from graphene sheet has emerged as a unique class of carbon materials, holding promising potentials for diverse applications such as catalysis, environmental remediation, tissue engineering, and most importantly as energy conversion and storage devices. [1][2][3][4][5] GA has ultralow densities, extremely high porosity, good mechanical flexibility, and interconnected hierarchical porous system, while keeping 2D graphene sheets effectively interconnected and stabilized in 3D free space as well as retaining the excellent properties of few-layer graphene such as surface area, electrical conductivity, and mechanical strength. [6][7][8] Thus GAs are more applicable in real applications than individual graphene sheet.The inherent features of GA are, in particular, beneficial for electrocatalysis and energy storage devices (e.g., supercapacitor, lithium-ion battery, metal-air batteries) which features high volumetric energy density, [9][10][11] because GA introduces following three substantial impartments: (i) The hierarchical porous network with continuous meso-(2-50 nm), macro-(50-10 000 nm), and supermacro-pore (>10 µm) system that leads to a dramatic increase in the amount of liquids from the outside environment and accessible two-phase boundaries in the aerogel architecture, thus effectively eliminating the mass transport issue; [9] (ii) interconnected graphene framework facilitates effective electron/ion transport; and (iii) the graphene sheets can act as ideal supports for growing or anchoring functional metal or semiconductor nanomaterials leading to synergistic chemical coupling effects while avoiding the use of any capping agent.To date, various synthetic strategies for fabricating GA have been successfully developed and these can be generalized into two types, namely, top-down and bottom-up strategies. Topdown methods such as chemical vapor deposition (CVD) and epitaxial growth use predesigned sacrificial hard or soft template, which defines the structure morphology and nature of porosity. However, high temperature process (500-1000 °C) and tedious treatment hamper their commercialization; moreover, the degree of structure hierarchy is strictly limited. In general, successful anchoring of foreign active phases onto GA requires 3D graphene aerogel (GA) integrated with active metal or its derivatives has emerged as a novel class of multifunctional constructs with range of potential applications. However, GA fabricated by self-assembly in the liquid phase still suffers from low conductivity and poor knowledge related to spatial active phase distribution and 3D structure. To address these issues, a facile approach involving in situ integration of 1D silver nanowire (AgNW) during gelation of graphene oxide flakes is presented. AgNWs prevent the restacking of graphene sheets and act as an efficient electron highway and Ag source for deposition of ultrasmall Ag nanocrystals (AgNCs). When applied as the cathodic electrocatalyst in a zinc-...

The synergy between Pd atoms, CNT and MnO2 gives rises to significantly enhanced activity, selectivity and stability of Pd/MnO2–CNT for oxygen electrocatalysis. The assembled rechargeable metal air battery delivered high performance with enhanced cycling stability.

Hydrogen spillover is the phenomenon where a hydrogen atom, generated from the dissociative chemisorption of dihydrogen on the surface of a metal species, migrates from the metal to the catalytic support. This phenomenon is regarded as a promising avenue for hydrogen storage, yet the atomic mechanism for how the hydrogen atom can be transferred to the support has remained controversial for decades. As a result, the development of catalytic support for such a purpose is only limited to typical reducible oxide materials. Herein, by using a combination of in situ spectroscopic and imaging technique, we are able to visualize and observe the atomic pathway for which hydrogen travels via a frustrated Lewis pair that has been constructed on a nonreducible metal oxide. The interchangeable status between the hydrogen, proton, and hydride is carefully characterized and demonstrated. It is envisaged that this study has opened up new design criteria for hydrogen storage material.

Ni y P emerged as a highly active precatalyst for the alkaline oxygen evolution reaction where structural changes play a crucial role for its catalytic performance. We probed the chemical stability of Ni y P in 1 M KOH at 80 °C and examined how exposure up to 168 h affects its structure and catalytic performance. We observed selective P-leaching and formation of Ni y P/NiOx core−shell heterostructures, where shell thickness increases with ageing time, which is detrimental for the activity. By tuning the particle size, we demonstrate that prevention of complete catalyst oxidation is essential to preserve the outstanding electrochemical performance of Ni y P in alkaline media.

Traditionally, bandgap materials are a prerequisite to photocatalysis since they can harness a reasonable range of the solar spectrum. However, the high impedance across the bandgap and the low concentration of intrinsic charge carriers have limited their energy conversion. By contrast, metallic nanoparticles possess a sea of free electrons that can effectively promote the transition to the excited state for reactions. Here, an atomic layer of a bimetallic concoction of silver-gold shells is precisely fabricated onto an Au core via a sonochemical dispersion approach to form a core-shell of Au-Ag that exploits the wide availability of excited states of Ag while maintaining an efficient localized surface plasmon resonance (LSPR) of Au. Catalytic results demonstrate that this mix of Ag and Au can convert solar energy to hydrogen at high efficiency with an increase of 112.5% at an optimized potential of −0.5 V when compared to light-off conditions under the electrochemical LSPR. This outperforms the commercial Pt catalysts by 62.1% with a hydrogen production rate of 1870 µmol g −1 h −1 at room temperature. This study opens a new route for tuning the range of light capture of hydrogen evolution reaction catalysts using fabricated core-shell material through the combination of LSPR with electrochemical means.

Developing transition metal oxides (TMOs) electrocatalysts with high bifunctional activity is of significance for reversible fuel cells and rechargeable metal air batteries. Herein, we report a bifunctional nitrogen doped NiCoOx...

Xiaopeng Li, Yuhan Sun, and co‐workers report on the 3D metallic active phase distribution in a self‐assembled composite graphene aerogel. Unraveled by X‐ray μCT presented in article https://doi.org/10.1002/adfm.201700041, the interconnected 3D silver networks hold potential to achieve high oxygen reduction activity and ultra‐high rate performance in Zn‐air batteries.