Generation of Pure Oxygen from Briny Water by Binary Catalysis.

Whereas the emphasis of water splitting is typically on hydrogen generation, there is value in the oxygen produced, especially in the undersea environment and for medicinal applications in the developing world. The generation of pure and breathable oxygen from abundant and accessible sources of water, such as brine and seawater, is challenging owing to the prevalence of the competing halide oxidation reaction to produce halogen and hypohalous acids. We show here that pure O2 may be generated from briny water by using an oxygen evolution catalyst with an overlayer that fulfills the criteria of (i) possessing a point of zero charge that results in halide anion rejection and (ii) promoting the disproportionation of hypohalous acids.

Role of electrolyte composition on the acid stability of mixed-metal oxygen evolution catalysts.

Acid stability in catalysts that promote the oxygen evolution reaction (OER) may be achieved through either the introduction of electrolyte-modulated self-healing processes, or the fixation of OER active sites within stable, conductive oxide matricies. By varying the nature of the electrolyte, pH, buffer concentration, and ionic strength, the contributions of these two effects may be deconvoluted. Furthermore, we find that the nature of the buffer is capable of engendering OER with exceptional acid stability at moderate overpotentials.

Template-stabilized oxidic nickel oxygen evolution catalysts.

Earth-abundant oxygen evolution catalysts (OECs) with extended stability in acid can be constructed by embedding active sites within an acid-stable metal-oxide framework. Here, we report stable NiPbOx films that are able to perform oxygen evolution reaction (OER) catalysis for extended periods of operation (>20 h) in acidic solutions of pH 2.5; conversely, native NiOx catalyst films dissolve immediately. In situ X-ray absorption spectroscopy and ex situ X-ray photoelectron spectroscopy reveal that PbO2 is unperturbed after addition of Ni and/or Fe into the lattice, which serves as an acid-stable, conductive framework for embedded OER active centers. The ability to perform OER in acid allows the mechanism of Fe doping on Ni catalysts to be further probed. Catalyst activity with Fe doping of oxidic Ni OEC under acid conditions, as compared to neutral or basic conditions, supports the contention that role of Fe3+ in enhancing catalytic activity in Ni oxide catalysts arises from its Lewis acid properties.

Selective Production of Oxygen from Seawater by Oxidic Metallate Catalysts.

Although the emphasis of water splitting is typically on hydrogen generation, there is a value in the oxygen byproduct especially for life support in field operations. For such applications, the production of a pure, unadulterated oxygen stream is highly desired under environmental conditions. Here, we demonstrate that self-healing oxygen evolution catalysts composed of cobalt or nickel are capable of selectively producing oxygen from both 0.5 M NaCl solutions and seawater. Differential electrochemical mass spectrometry demonstrates the absence of halogen in the product stream, and chemical analysis shows the production of only minute amounts of hypohalous acid.

Efficient Conversion of CO2 to CO Using Tin and Other Inexpensive and Easily Prepared Post-Transition Metal Catalysts.

The development of affordable electrocatalysts that can drive the reduction of CO2 to CO with high selectivity, efficiency, and large current densities is a critical step on the path to production of liquid carbon-based fuels. In this work, we show that inexpensive triflate salts of Sn(2+), Pb(2+), Bi(3+), and Sb(3+) can be used as precursors for the electrodeposition of CO2 reduction cathode materials from MeCN solutions, providing a general and facile electrodeposition strategy, which streamlines catalyst synthesis. The ability of these four platforms to drive the formation of CO from CO2 in the presence of [BMIM]OTf was probed. The electrochemically prepared Sn and Bi catalysts proved to be highly active, selective, and robust platforms for CO evolution, with partial current densities of jCO = 5-8 mA/cm(2) at applied overpotentials of η < 250 mV. By contrast, the electrodeposited Pb and Sb catalysts do not promote rapid CO generation with the same level of selectivity. The Pb material is only ∼10% as active as the Sn and Bi systems at an applied potential of E = -1.95 V and is rapidly passivated during catalysis. The Sb-comprised cathode material shows no activity for conversion of CO2 to CO under analogous conditions. When taken together, this work demonstrates that 1,3-dialkylimidazoliums can promote CO production, but only when used in combination with an appropriately chosen electrocatalyst material. More broadly, these results suggest that the interactions between CO2, the imidazolium promoter, and the cathode surface are all critical to the observed catalysis.

Ranking and selection of motor carrier safety performance by commodity.

We use recent safety performance data to rank US motor carrier commodity segments (e.g., Tank segment or Produce segment) in terms of several driver-related, vehicle-related, and crash-related safety measures. Ranking and selection inference techniques are used to determine the best and worst performing commodity segments at the 95% confidence level. The results are mixed, however the Passenger segment is generally best, while the Produce, Intermodal, and Refrigerated segments tend to be worst.