During hydrogen production for (renewable) energy storage, direct seawater electrolysis offers several notable advantages over freshwater electrolysis. Unfortunately, it is also hindered by... Show moreDuring hydrogen production for (renewable) energy storage, direct seawater electrolysis offers several notable advantages over freshwater electrolysis. Unfortunately, it is also hindered by possible oxidation reactions of chloride and (to a lesser extent) bromide, which can occur in parallel to the evolution of oxygen and form harmful by-products at the anode. Although the respective oxidation reactions of Br- and Cl- have been researched quite well on Pt, not much is known concerning bromide oxidation and its effect on the evolution of chlorine and oxygen for metal oxides, which are the class of electrocatalysts overwhelmingly used in industry. Using glassy carbon-supported iridium oxide (IrOx) as a model system, we investigated the oxidation behaviour of this well-known oxygen evolution catalyst in an acidic Br-/Cl- electrolyte. We first briefly discuss the solution chemistry and oxidation products that may be expected. Model studies were performed of the parallel evolution of Br-2, Cl-2 and O-2 to increase the understanding of the anodic competition problem, with a special focus on the selectivity towards oxygen. Using rotating ring-disk voltammetry and UV-Vis spectroscopy, our results suggest that bromide and chloride competitively absorb on IrOx, but do not alter each other's oxidation reaction mechanisms, which both seem to adhere best to a Volmer-Heyrovsky mechanism. We also find that bromide and chloride adsorption significantly slow down the oxygen evolution reaction, in an additive way. Even a relatively small amount of bromide highly affected the oxygen evolution selectivity. Formation of the interhalogen compound BrCl, which is possible in a mixed Br-/Cl- electrolyte, does not seem to occur. (C) 2020 The Authors. Published by Elsevier Inc. Show less
Hydrogen production from seawater electrolysis is highly promising for the capture and storage of intermittent renewable energy, but is hindered by the possibility of unwanted reactions at the... Show moreHydrogen production from seawater electrolysis is highly promising for the capture and storage of intermittent renewable energy, but is hindered by the possibility of unwanted reactions at the anode. The oxidation reactions of chloride and (to a lesser extent) bromide, which can occur in parallel to the evolution of oxygen, lead to environmentally harmful by-products and thus represent undesirable side-reactions. We present some general considerations of solution chemistry and oxidation products that may be expected in a mixed acidic bromide/chloride electrolyte. We performed electrochemical model studies of the simultaneous oxidation of bromide and chloride and their mutual interaction on a Pt electrocatalyst, with the aim of deepening the general understanding of the anodic competition problem. Using simplified model systems, our findings suggest that the oxidation of bromide is hindered by competing chloride adsorption, in a way that can be quite satisfactorily modelled by a simple Langmuir isotherm describing the competing adsorption and reactivity of all species. The oxidation of chloride was however not properly captured by this same model, and may be substantially different. Furthermore, the formation of the interhalogen compound BrCl seems to occur in-between the oxidation of bromide and chloride. Show less
Anton-Garcia, D.; Apfel, U.-P.; Andrei, V.; Aitchison, C.M.; Badiani, V.; Beller, M.; ... ; Zwijnenburg, M.A. 2019
Solar-powered electrochemical production of hydrogen through water electrolysis is an active and important research endeavor. However, technologies and roadmaps for implementation of this process... Show moreSolar-powered electrochemical production of hydrogen through water electrolysis is an active and important research endeavor. However, technologies and roadmaps for implementation of this process do not exist. In this perspective paper, we describe potential pathways for solar-hydrogen technologies into the marketplace in the form of photoelectrochemical or photovoltaic-driven electrolysis devices and systems. We detail technical approaches for device and system architectures, economic drivers, societal perceptions, political impacts, technological challenges, and research opportunities. Implementation scenarios are broken down into short-term and long-term markets, and a specific technology roadmap is defined. In the short term, the only plausible economical option will be photovoltaic-driven electrolysis systems for niche applications. In the long term, electrochemical solar-hydrogen technologies could be deployed more broadly in energy markets but will require advances in the technology, significant cost reductions, and/or policy changes. Ultimately, a transition to a society that significantly relies on solar-hydrogen technologies will benefit from continued creativity and influence from the scientific community. Show less
Asian New Religious Movements are attracting converts in every continent. They offer members a comprehensive cultural system of beliefs, rituals, daily routines, diet, dress styles and patterns of... Show moreAsian New Religious Movements are attracting converts in every continent. They offer members a comprehensive cultural system of beliefs, rituals, daily routines, diet, dress styles and patterns of relationship. While often based on pre-modern Asian values and practices, these are accepted by converts from a global sweep of cultures without modification. As agents promoting the truly global application of holistic cultural systems, they warrant our attention. Show less
