Atomically dispersed Pt-N-4 sites as efficient and selective electrocatalysts for the chlorine evolution reaction

Chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. Although precious metal-based mixed metal oxides (MMOs) have been widely used as CER catalysts, they suffer from the concomitant generation of oxygen during the CER. Herein, we demonstrate that atomically dispersed Pt-N-4 sites doped on a carbon nanotube (Pt-1/CNT) can catalyse the CER with excellent activity and selectivity. The Pt-1/CNT catalyst shows superior CER activity to a Pt nanoparticle-based catalyst and a commercial Ru/Ir-based MMO catalyst. Notably, Pt-1/CNT exhibits near 100% CER selectivity even in acidic media, with low Cl- concentrations (0.1M), as well as in neutral media, whereas the MMO catalyst shows substantially lower CER selectivity. In situ electrochemical X-ray absorption spectroscopy reveals the direct adsorption of Cl- on Pt-N-4 sites during the CER. Density functional theory calculations suggest the PtN4C12 site as the most plausible active site structure for the CER

Facile deposition of Pt nanoparticles on Sb doped SnO2 support with outstanding active surface area for the oxygen reduction reaction

Understanding the influence of the support on the electrocatalytic behaviour of platinum is key to the development of novel Pt oxide catalysts for the oxygen reduction reaction ORR . For studies to isolate these effects, highly dispersed supported Pt nanoparticles with well controlled particle sizes are required. In this study, we demonstrate a novel preparation process for Pt oxide catalysts, with small Pt nanoparticles 2.5 3.5 nm , supported on a commercial Sb SnO2 ATO nanopowder, with a very high utilization of the Ptprecursor. The organometallic chemical deposition method produces catalyst nanoparticles with a homogeneous distribution over the surface of the support even at high Pt metal loadings. Additionally, by using a mild hydrogen reduction treatment of the oxide support prior to Pt deposition, significantly smaller Pt nanoparticles were obtained with an outstanding mass specific electrochemically active surface area exceeding 100 m2 g amp; 8722;1. Furthermore, by varying the Pt metal loading, several fundamental electrocatalytic effects that strongly influence the Pt ATO system were distinguished. Good electrochemical stability during high potential cycling was observed and was attributed to potential dependent in situ conductivity switching of the ATO support. In turn, ORR activities of the Pt ATO catalysts were found to be influenced by a combination of Pt particle size effects, ATO support in situ conductivity limitations at PEFC operation potentials, and electrocatalytic metal support interactions. Therefore, in addition to demonstrating a powerful method for the preparation of exceptionally high surface area Pt oxide catalysts, the present study contributes to the detailed understanding of the interplay between various phenomena that influence the electrocatalytic activity and stability of Pt oxide systems for the ORR. Furthermore, the novel preparation approach for Pt metal oxide catalysts could be of major interest for catalyst preparation in other fields of electrocatalysis and heterogeneous catalysi

Anion-Tuned Layered Double Hydroxide Anodes for Anion Exchange Membrane Water Electrolyzers: From Catalyst Screening to Single-Cell Performance

Anion exchange membrane water electrolysis (AEMWE) is an attractive emerging green hydrogen technology. However, the scaling of trends in activity of anode catalysts for the oxygen evolution reaction (OER) from a liquid-electrolyte, three-electrode environment to the two-electrode single-cell format has remained poorly considered. Herein, we critically investigate the scaling of kinetic and catalytic properties of a family of highly active Ni foam (NF) supported, anion (A–)-tuned NiFe(-A–)-OER catalysts. Trends in catalytic activity suggest impressive improvements of up to 91-fold in three-electrode setups (3LC) compared to uncoated NF. While we demonstrate the successful qualitative structure–performance tunability in a 5 cm2 AEMWE single cell, we also find serious limitations in the quantitative predictability of three-electrode setups for single-cell performance trends. Cell environments appear to equalize the cell performances of designer catalysts, which has important ramifications for electrode development. We succeed in analyzing and discussing some of these translation limitations in terms of previously overlooked effects summarized in the activity improvement factor f

Stabilization of Pt Nanoparticles Due to Electrochemical Transistor Switching of Oxide Support Conductivity

Polymer electrolyte fuel cells (PEFCs) offer an efficient way of chemical-to-electrical energy conversion that could drastically reduce the environmental footprint of the mobility and stationary energy supply sectors, respectively. However, PEFCs can suffer from severe degradation during start/stop events, when the cathode catalyst is transiently exposed to very high potentials. In an attempt to mitigate corrosion of conventional carbon support materials for Pt catalyst nanoparticles under these conditions, conductive metal oxides like antimony-doped tin oxide (ATO) are considered alternative support materials with improved corrosion resistance. A combined in situ anomalous small-angle X-ray scattering and post mortem transmission electron microscopy study reveals PEFC-relevant degradation properties of ATO-supported Pt in comparison to carbon-supported Pt catalysts. Against expectation, the superior stability of ATO-supported Pt nanoparticles cannot be merely explained by improved support corrosion resistance. Instead, the dominant loss mechanism of electrochemical Ostwald ripening is strongly suppressed on ATO support, which can be explained with a potential-dependent switching of support oxide surface conductivity. This electrochemical transistor effect represents an important design principle for the development of optimized metal oxide support materials that protect supported Pt nanoparticles at high potentials, where careful consideration of the metal oxide flat-band potential is required in order to maintain high catalyst performance at normal PEFC cathode operation conditions at the same time