CO reduction is of significant interest for the production of nonfossil fuels. The reactivity of eight Cu foams with substantially different morphologies was comprehensively investigated by analysis of the product spectrum and in situ electrochemical spectroscopies (X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray photoelectron spectroscopy, and Raman spectroscopy). The approach provided new insight into the reactivity determinants: The morphology, stable Cu oxide phases, and *CO poisoning of the H formation reaction are not decisive; the electrochemically active surface area influences the reactivity trends; macroscopic diffusion limits the proton supply, resulting in pronounced alkalization at the CuCat surfaces (operando Raman spectroscopy). H and CH formation was suppressed by macroscopic buffer alkalization, whereas CO and C H formation still proceeded through a largely pH-independent mechanism. C H was formed from two CO precursor species, namely adsorbed *CO and dissolved CO present in the foam cavities.

Selective electrochemical reduction of CO2 is an emerging field which needs more active and stable catalysts for its practicability. In this work, we have studied the influence of Ag metal incorporation into Cu dendritic structures on the product distribution and selectivity of CO2 electroreduction. Bimetallic AgCu foams prepared by hydrogen bubble templated electrodeposition shift the potentials of CO production to more positive values compared to bulk silver. The presence of Ag during the electrodeposition significantly changed the size and the shape of the dendrites in the pore walls of AgCu foams compared to Cu foam. The CO adsorption characteristics are studied by operando Raman spectroscopy. In the presence of Ag, the maximum CO adsorption is observed at a more positive potential. As a result, an improved selectivity for CO is obtained for AgCu foam catalysts at lower overpotentials compared to Cu foam catalyst, evidencing a synergistic effect between the bimetallic components. We were successful in increasing the CO mass activity with respect to the total Ag amount. AgCu foams are found to retain the CO selectivity during long-term operation, and with their easily scalable electrodeposition synthesis they possess high potential for industrial application.

Nanotube assemblies represent an emerging class of advanced functional materials, whose utility is however hampered by intricate production processes. In this work, three classes of nanotube networks (monometallic, bimetallic, and metal oxide) are synthesized solely using facile redox reactions and commercially available ion track membranes. First, the disordered pores of an ion track membrane are widened by chemical etching, resulting in the formation of a strongly interconnected pore network. Replicating this template structure with electroless copper plating yields a monolithic film composed of crossing metal nanotubes. We show that the parent material can be easily transformed into bimetallic or oxidic derivatives by applying a second electroless plating or thermal oxidation step. These treatments retain the monolithic network structure but result in the formation of core-shell nanotubes of altered composition (thermal oxidation: CuO-CuO; electroless nickel coating: Cu-Ni). The obtained nanomaterials are applied in the enzyme-free electrochemical detection of glucose, showing very high sensitivities between 2.27 and 2.83 A M cm. Depending on the material composition, varying reactivities were observed: While copper oxidation reduces the response to glucose, it is increased in the case of nickel modification, albeit at the cost of decreased selectivity. The performance of the materials is explained by the network architecture, which combines the advantages of one-dimensional nano-objects (continuous conduction pathways, high surface area) with those of a self-supporting, open-porous superstructure (binder-free catalyst layer, efficient diffusion). In summary, this novel synthetic approach provides a fast, scalable, and flexible route toward free-standing nanotube arrays of high compositional complexity.

Cobalt‐incorporated nitrogen‐doped reduced graphene oxide (Co/NrGO) as a catalyst for the oxygen reduction reaction is prepared in a single step by thermal reduction of graphene oxide to reduced graphene oxide (rGO) in the presence of a cobalt salt and 1,10‐phenanthroline as a nitrogen precursor. Cobalt is identified as cobalt oxide (CoO) in the hybrid. Both the cobalt and nitrogen contents in Co/NrGO are higher than those in cobalt‐ or nitrogen‐free samples; this indicates that cobalt and 1,10‐phenathroline mutually enhance incorporation into the material. An almost four‐electron transfer is observed as the average per oxygen molecule, and Co/NrGO demonstrates highly improved activity in comparison with NrGO and rGO. CoO and nitrogen‐doped moieties may be acting as active centers for oxygen reduction individually or synergistically. With a loading of less than 2 wt % cobalt in Co/NrGO, appreciable activity is already observed. Moreover, the high selectivity for oxygen reduction over methanol oxidation for Co/NrGO is demonstrated, making this hybrid a promising catalyst for direct methanol alkaline fuel cells.

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Herein, honeycomb nickel-, cobalt-and iron-doped Cu 2 O/Cu foams with dendrite-like structures are in-situ formed atop of a copper foil substrate using the facile and low-cost dynamic hydrogen bubbles template technique (DHBT), wherein the copper nanoparticles are electrodeposited and grow in the interstitial spaces between the hydrogen bubbles. The incorporation of nickel, cobalt and iron impurities (less than 4%) into the Cu 2 O/Cu structures improved their performance significantly for various electrochemical reactions including water splitting, glucose and glycerol electrooxidation. This outstanding enhancement is attributed to the catalysts dendritic structures providing an easily accessible high active surface area. In addition, the doped metals are believed to increase the electrochemically active surface area and to facilitate the electron transfer in the studied reactions. Besides, the presence of these dopants improved the adsorption of glucose and glycerol molecules on the copper surface active sites together with increasing the Cu 2 O's inherent conductivity.

Reliable electrochemical testing protocols assessing the catalytic performance of novel materials, such as the rotating disk electrode method to determine the oxygen reduction reaction activity, play an essential role in the knowledge-based design of tailored electrocatalysts. However, these techniques are unable to accurately predict the performance of the developed electrocatalysts in membrane electrode assemblies (MEAs) which are ultimately used in full fuel cell measurements. Half-cell tests of gas diffusion electrodes have been shown to be a good compromise, with economical use of electrocatalysts while also mimicking the three-phase boundary in MEA during the presence of humidified reactant gas. In this review, we aim for a bird’s eye view of the set-ups already reported, how the testing protocols differ and how the protocols can be unified for a more consistent performance evaluation.

Phase-pure spinel Ni2FeS4 nanosheets with a specific surface area of 80 m2 g–1 were successfully prepared via fast and energy-saving microwave-assisted nonaqueous sol–gel synthesis, starting from metal acetylacetonates and benzyl mercaptan as the sulfur source. Synthesized nanosheets were characterized thoroughly by X-ray diffraction including Rietveld refinement, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, electron microscopy, nitrogen and water vapor physisorption measurements, and thermogravimetric analysis coupled with mass spectrometry. Such noble metal free Ni2FeS4 nanosheets were successfully applied as electrocatalyst for the aqueous carbon dioxide reduction reaction, yielding selectively the syngas components hydrogen and carbon monoxide.