Deposition Of Inorganic Compounds Research Articles

Enhanced Electrochemical Performance of Supercapacitors via Atomic Layer Deposition of ZnO on the Activated Carbon Electrode Material.

Fabricating electrical double-layer capacitors (EDLCs) with high energy density for various applications has been of great interest in recent years. However, activated carbon (AC) electrodes are restricted to a lower operating voltage because they suffer from instability above a threshold potential window. Thus, they are limited in their energy storage. The deposition of inorganic compounds’ atomic layer deposition (ALD) aiming to enhance cycling performance of supercapacitors and battery electrodes can be applied to the AC electrode materials. Here, we report on the investigation of zinc oxide (ZnO) coating strategy in terms of different pulse times of precursors, ALD cycles, and deposition temperatures to ensure high electrical conductivity and capacitance retention without blocking the micropores of the AC electrode. Crystalline ZnO phase with its optimal forming condition is obtained preferably using a longer precursor pulse time. Supercapacitors comprising AC electrodes coated with 20 cycles of ALD ZnO at 70 °C and operated in TEABF4/acetonitrile organic electrolyte show a specific capacitance of 23.13 F g−1 at 5 mA cm−2 and enhanced capacitance retention at 3.2 V, which well exceeds the normal working voltage of a commercial EDLC product (2.7 V). This work delivers an additional feasible approach of using ZnO ALD modification of AC materials, enhancing and promoting stable EDLC cells under high working voltages.

Effects of nitrate and sulfate on greenhouse gas emission potentials from microform-derived peats of a boreal peatland: A 13C tracer study

Increasing natural and anthropogenic deposition of nitrate (NO3−) and sulfate (SO42−) to peatlands may modify CH4 oxidation, CO2 and N2O production, thereby affecting the balance of greenhouse gases (GHG) globally. Among environmental factors controlling these biogeochemical processes, effects of peatland microrelief are poorly understood. Fluxes of CO2, CH4 and N2O were measured before and after incubation with NO3− and SO42− for peat samples collected from various microrelief positions of a boreal oligotrophic mire in Eastern Finland. Soil was spiked with 13CH4 to understand the processes of CH4 oxidation, its microbial utilization and incorporation into soil organic matter (SOM). We hypothesized that the addition of NO3− and SO42− would 1) stimulate CO2 and N2O production (nutritional effect), but 2) decrease CH4 oxidation due to acceleration of other more energetically favorable processes (e.g. denitrification), and 3) these patterns should follow the naturally established aerobic zone of a microform type and decrease with depth.Microbial biomass (MB) at 50 cm below all microforms was 9–15 folds higher than in the topsoil. MB controlled the GHG dynamics and was related to specific depth-dependent environmental conditions, rather than oxygen availability. Indeed, production of CO2 and N2O, and oxidation potentials of CH4 revealed no clear linkage with the naturally established aeration zone of the peatland’s microforms. Following NO3− and SO42− addition, production of CO2 decreased by 20–65% compared to the control, with the greatest reduction in CO2 emission occurring in the topsoil of hollows. In turn, CH4 oxidation was suppressed by 20–94% with NO3− addition at 50 cm in lawns and with both NO3− and SO42− at 50 cm in hollows. The N2O production was increased up to 180–240 times under NO3− treatment at 50 cm in hollows and lawns. In conclusion, human-induced deposition of NO3− and SO42− may suppress CO2 emissions from and CH4 oxidation by boreal oligotrophic mires especially under the conditions of deposition increase. Finally, the deposition of inorganic compounds is strongly important to be considered in the estimation of ecosystem C and N balances.