High-Performance Hydroxide Exchange Membrane Fuel Cell Comprising an Atomic Layer-Deposited Silver Cathode.

Atomic layer deposition (ALD) is emerging as an efficient tool for the precise manufacture of catalysts, owing to its sophisticated surface tailoring capabilities. To overcome the techno-economic limitations of fuel cell electric vehicles (FCEVs), which are considered suitable alternatives to battery electric vehicles (BEVs), the development of cost-efficient high-performance catalysts is essential. In this study, we successfully fabricated a Pt-free cathode for a hydroxide exchange membrane fuel cell (HEMFC) with excellent oxygen reduction activity under extremely low loading of Ag electrocatalysts using ALD. Microstructural analysis confirmed that the surface modification by ALD-Ag nanoparticles exhibited excellent step coverage characteristics on porous carbon nanotubes (CNTs). An HEMFC comprising a CNT cathode surface-decorated with ALD-Ag nanoparticles delivered a high peak power density of 2154 mW mgAg-1 in an alkaline environment at 65 °C. This study demonstrates the applicability of ALD for the manufacture of highly active low-cost electrocatalysts for high-performance HEMFCs.

Nanoporous silver cathode surface treated by atomic layer deposition of CeO(x) for low-temperature solid oxide fuel cells.

We evaluated the performance of solid oxide fuel cells (SOFCs) with a 50 nm thin silver (Ag) cathode surface treated with cerium oxide (CeO(x)) by atomic layer deposition (ALD). The performances of bare and ALD-treated Ag cathodes were evaluated on gadolinia-doped ceria (GDC) electrolyte supporting cells with a platinum (Pt) anode over 300 °C-450 °C. Our work confirms that ALD CeO(x) treatment enhances cathodic performance and thermal stability of the Ag cathode. The performance difference between cells using a Ag cathode optimally treated with an ALD CeO(x) surface and a reference Pt cathode is about 50% at 450 °C in terms of fuel cell power output in our experiment. The bare Ag cathode completely agglomerated into islands during fuel cell operation at 450 °C, while the ALD CeO(x) treatment effectively protects the porosity of the cathode. We also discuss the long-term stability of ALD CeO(x)-treated Ag cathodes related to the microstructure of the layers.

Highly Active Oxygen Evolution on Carbon Fiber Paper Coated with Atomic-Layer-Deposited Cobalt Oxide.

In this work, we evaluated the oxygen evolution performance of cobalt oxide (CoO x)-coated carbon fiber paper in electrochemical water splitting. For a uniform coating of CoO x layers along the carbon fiber paper, the atomic layer deposition (ALD) technique was applied. We achieved a uniform and conformal coating of atomic-layer-deposited CoO x (ALD-CoO x) on the carbon fiber paper. The overpotential for oxygen evolution measured for the optimized ALD-coated carbon fiber paper was as low as 343 mV at 10 mA cm-2, which is competitive with the activity of state-of-the-art CoO x prepared on electrodes with large surface areas. Oxygen evolution is not enhanced after a critical thickness, about 28 nm in our study, is reached. The optimal thickness of the ALD-CoO x film is dependent on two competing effects: the high oxidation state of cobalt ions in thicker CoO x helps the oxygen evolution, whereas the introduction of a thick oxide coating decelerates the rate of charge transfer at the surface.

Fabrication of Lanthanum Strontium Cobalt Ferrite-Gadolinium-Doped Ceria Composite Cathodes Using a Low-Price Inkjet Printer.

In this work, we have successfully fabricated lanthanum strontium cobalt ferrite (LSCF)-gadolinium-doped ceria (GDC) composite cathodes by inkjet printing and demonstrated their functioning in solid oxide fuel cells (SOFCs). The cathodes are printed using a low-cost HP inkjet printer, and the LSCF and GDC source inks are synthesized with fluidic properties optimum for inkjet printing. The composition and microstructure of the LSCF and GDC layers are successfully controlled by controlling the color level in the printed images and the number of printing cycles, respectively. Anode-support type SOFCs with optimized LSCF-GDC composite cathodes synthesized by our inkjet printing method have achieved a power output of over 570 mW cm-2 at 650 °C, which is comparable to the performance of a commercial SOFC stack. Electrochemical impedance analysis is carried out to establish a relationship between the cell performance and the compositional and structural characteristics of the printed LSCF-GDC composite cathodes.