The next generation of high-performance batteries should include alternative chemistries that are inherently safer to operate than nonaqueous lithium-based batteries. Aqueous zinc-based batteries can answer that challenge because monolithic zinc sponge anodes can be cycled in nickel-zinc alkaline cells hundreds to thousands of times without undergoing passivation or macroscale dendrite formation. We demonstrate that the three-dimensional (3D) zinc form-factor elevates the performance of nickel-zinc alkaline cells in three fields of use: (i) >90% theoretical depth of discharge (DOD) in primary (single-use) cells, (ii) >100 high-rate cycles at 40% DOD at lithium-ion-commensurate specific energy, and (iii) the tens of thousands of power-demanding duty cycles required for start-stop microhybrid vehicles.

No abstract

ZnS nanoparticle (NP) gel networks were used as cation exchange materials for the removal of Pb(2+) and Hg(2+) from aqueous solutions. First, the suitability of the gel as a remediation material was studied by analyzing the mechanism of the cation exchange reaction. ZnS NP gels can exchange with other divalent cations (Pb(2+), Hg(2+)) under mild reaction conditions. The speed of the reaction is influenced by the reduction potential of the incoming cation. The ZnS aerogels can remove Pb(2+) and Hg(2+) from aqueous solutions with a wide range of initial concentrations. For initial Pb(2+) concentrations of 100 ppb, the Pb(2+) concentration can be reduced below the action limit established by the EPA (15 ppb). Under thermodynamically forcing conditions, the water remediation capacity of the ZnS NP aerogels was determined to be 14.2 mmol Pb(2+)/ g ZnS aerogel, which is the highest value reported to date.

The historically poor electrochemical rechargeability of Zn in alkaline electrolyte has hindered the commercial viability of Ni-Zn batteries, a system otherwise of interest because of high specific energy (up to 140 Wh kg -1 ). We have redesigned the Zn anode as a three-dimensional (3D), monolithic porous architecture ("sponge") that exhibits unprecedented Zn specific capacity and dendrite-free cycling. Maintaining the integrity of the 3D Zn sponge architecture throughout charge-discharge is required to ultimately achieve technologically relevant performance in terms of cycle life and capacity. En route to this goal, we systematically evaluated a series of electrolyte and electrode additives used in conjunction with our Zn sponge anode in order to down-select formulations that minimize electrode shape change with cycling in prototype Ni-3D Zn cells. The classes of additives chosen for this study include those that either inhibit ZnO passivation during discharge (Type I: LiOH, K 2 SiO 3 ) or promote it (Type II/III: KF, K 2 CO 3 , ZnO, Ca(OH) 2 ), as well as combinations thereof. We find that the second class of additives effectively retains the cycled Zn sponge in its pre-cycled condition.

The rate constant of the reaction of Cl atoms with methacrolein (k(1)) has been measured relative to that of Cl with propane (k(2)) or cyclohexane (k(6)) at ambient temperature and pressures varying from 1-950 Torr. The experiments were carried out by irradiation (350 nm) of Cl(2)/methacrolein/propane or cyclohexane mixtures in N(2) or N(2)/O(2) diluent at ambient temperature in a spherical (500 cm(3)) Pyrex reactor (GC/FID analyses) or a 140 L FTIR smog chamber. The measured relative rate constant ratios in the GC/FID experiments were k(1)/k(2) = 1.464 +/- 0.015(2sigma) in N(2) and k(1)/k(2) = 1.68 +/- 0.03(2sigma) in N(2)/O(2) diluent (O(2) > 20,000 ppm). No pressure dependence was observed over the range studied in N(2) (120-950 Torr) using the GC/FID. In the FTIR/smog chamber experiments values of k(1)/k(6) = 0.645 +/- 0.032, 0.626 +/- 0.037, 0.586 +/- 0.026, and 0.479 +/- 0.024 were measured in 700, 100, 10, and 1 Torr, respectively, of N(2) diluent. Using k(2) = (1.4 +/- 0.2) x 10(-10) and k(6) = (3.3 +/- 0.5) x 10(-10) high pressure limiting rate constants of k(1) = (2.05 +/- 0.3) x 10(-10) [GC/FID] and (2.13 +/- 0.34) x 10(-10) [FTIR] cm(3) molecule(-1) s(-1) were determined. In experiments using the GC/FID reactor with N(2) diluent the following products (molar yields) were observed: 2,3-dichloro-2-methylpropanal [(47.2 +/- 8)% excluding error in calibration]; methacryloyl chloride [(22.9 +/- 2)%]; and 2-chloromethylacrolein [(2.3 +/- 0.8)%]. Addition of 200 ppm O(2) (with Cl(2) = 5000 ppm) resulted in a sharp reduction of the 2,3-dichloro-2-methylpropanal yield (to approximately 2%) with an accompanying appearance of chloroacetone [yield = (55 +/- 7)% decreasing to (44 +/- 7)% in air diluent]. The methacryloyl chloride yield was 23% for [O(2)]/[Cl(2)] ratios from 0 to 0.2 but decreased to near zero as the O(2)/Cl(2) ratio was increased to approximately 400. The variation in methacryloyl chloride yield with the O(2)/Cl(2) ratio in the initial mixture allowed an approximate measurement of the rate constant for the reaction of the methacryloyl radical with O(2) relative to that with Cl(2) (k(O(2))/k(Cl(2)) = 0.066 +/- 0.02). In experiments using the FTIR reactor in 700 Torr of N(2) diluent, methacryloyl chloride [(26 +/- 3)%] and HCl [(27 +/- 3)%] were observed as products. In 700 Torr of air diluent, the observed products were: chloroacetone [(44 +/- 5)%], CO(2) [(27 +/- 3)%], HCl [(21 +/- 3)%], and HCHO [(14 +/- 2)%], and CH(3)C(O)CH(2)OH (3-4%). The observation of CH(3)C(O)CH(2)OH indicates the presence of OH radicals in the system. At atmospheric pressure and 297 K, the title reaction proceeds [(24.5 +/- 5)%] via abstraction of the aldehydic hydrogen atom, [(2.3 +/- 0.8)%] via abstraction from the -CH(3) group, and approximately [(47 +/- 8) %] via addition to the CH(2)=C < double bond with most of the addition occurring at the terminal carbon atom (uncertainties represent statistical 2sigma). The results are discussed with respect to the literature data.