Conformal oxide nanocoatings on electrodeposited 3D porous Ni films by atomic layer deposition

A versatile chemical synthesis procedure to obtain Al2O3 and Co2FeO4 nanolayers conformally coating a three-dimensional (3D) porous Ni film is presented. First, porous Ni is grown by hydrogen bubble template-assisted electrodeposition. Subsequently, Al2O3 and Co2FeO4 layers, with thickness ranging from 5 nm to 25 nm, are directly deposited onto the pore walls by atomic layer deposition, while maintaining the porous architecture and magnetic properties of the Ni scaffold. The crystal structure, thickness and distribution of elements within the composite coatings are investigated in detail. The resulting magnetic and wettability properties are assessed. Contact angle tests reveal that 3D porous Ni films become more hydrophilic after coating with Al2O3 or Co2FeO4. From a technological point of view, the obtained composite porous films could be appealing for applications like magnetically-actuated micro/nano-electromechanical systems (MEMS/NEMS) or bio-MEMS/NEMS, among others

Photodeposition‐Based Synthesis of TiO2@IrOx Core–Shell Catalyst for Proton Exchange Membrane Water Electrolysis with Low Iridium Loading

The widespread application of green hydrogen production technologies requires cost reduction of crucial elements. To achieve this, a viable pathway to reduce the iridium loading in proton exchange membrane water electrolysis (PEMWE) is explored. Herein, a scalable synthesis method based on a photodeposition process for a TiO2@IrOx core–shell catalyst with a reduced iridium content as low as 40 wt.% is presented. Using this synthesis method, titania support particles homogeneously coated with a thin iridium oxide shell of only 2.1 ± 0.4 nm are obtained. The catalyst exhibits not only high ex situ activity, but also decent stability compared to commercially available catalysts. Furthermore, the unique core–shell structure provides a threefold increased electrical powder conductivity compared to structures without the shell. In addition, the low iridium content facilitates the fabrication of sufficiently thick catalyst layers at decreased iridium loadings mitigating the impact of crack formation in the catalyst layer during PEMWE operation. It is demonstrated that the novel TiO2@IrOx core–shell catalyst clearly outperforms the commercial reference in single‐cell tests with an iridium loading below 0.3 mgIr cm−2 exhibiting a superior iridium‐specific power density of 17.9 kW gIr−1 compared to 10.4 kW gIr−1 for the commercial reference.A facile and scalable synthesis method for a TiO2@IrOx core–shell electrocatalyst is developed, and its stability and superior performance for the acidic oxygen evolution reaction compared to a commercial catalyst is demonstrated in both ex situ and single‐cell electrochemical measurements. imageGerman Research Foundation http://dx.doi.org/10.13039/501100001659Collaborative Research Centre 1452European Research Council http://dx.doi.org/10.13039/501100000781German Federal Ministry of Education and Research (BMBF

Bifunctional hydrous RuO2 nanocluster electrocatalyst embedded in carbon matrix for efficient and durable operation of rechargeable zinc-air batteries

Ruthenium oxide (RuO2) is the best oxygen evolution reaction (OER) electrocatalyst. Herein, we demonstrated that RuO2 can be also efficiently used as an oxygen reduction reaction (ORR) electrocatalyst, thereby serving as a bifunctional material for rechargeable Zn-air batteries. We found two forms of RuO2 (i.e. hydrous and anhydrous, respectively h-RuO2 and ah-RuO2) to show different ORR and OER electrocatalytic characteristics. Thus, h-RuO2 required large ORR overpotentials, although it completed the ORR via a 4e process. In contrast, h-RuO2 triggered the OER at lower overpotentials at the expense of showing very unstable electrocatalytic activity. To capitalize on the advantages of h-RuO2 while improving its drawbacks, we designed a unique structure (RuO2@C) where h-RuO2 nanoparticles were embedded in a carbon matrix. A double hydrophilic block copolymer-templated ruthenium precursor was transformed into RuO2 nanoparticles upon formation of the carbon matrix via annealing. The carbon matrix allowed overcoming the limitations of h-RuO2 by improving its poor conductivity and protecting the catalyst from dissolution during OER. The bifunctional RuO2@C catalyst demonstrated a very low potential gap (triangle EOER-ORR=ca. 1.0V) at 20 mA cm(-2). The Zn|| RuO2@C cell showed an excellent stability (i.e. no overpotential was observed after more than 40 h)