A. Thomya* and Y. Khunatron

Abstract: This research aimed to study the functional groups of active electrocatalysts on the chlorine-side electrode. Catalyst synthesis involved (RuxCoy)₃O₄, Co and Ru contents with different Ru/Co molar ratio of 1:9, 2:8, 3:7, 4:6, 5:5. Conditions of catalytic air furnace temperature ranged from 350°C to 500°C. The XRD patterns for catalyst samples confirmed the ruthenium oxide and cobalt oxide phases in the products. The EDS spectra detected ruthenium, cobalt and oxygen in the prepared catalysts. The SEM and TEM images showed more dispersion of catalyst ruthenium oxide on cobalt oxide support surface. Characterization using XRD revealed ~57 nm mean diameter of Co₃O₄ particle sizes, respectively, while TEM technique gave ~85.93 nm mean diameter of (Ru0.1Co0.9)₃O₄ particle size. The test results of catalyst properties using XRD, SEM, EDS, TEM, SAD techniques showed the same results. HCl was utilized for RFB by spraying the catalyst material in a range of 0.5-1 M on GDL, the chlorine-side, Carbon paper and Carbon cloth. With Carbon paper that had better discharge voltage efficiency, the 0.5 M treatment generated greatest current density and power density. The catalyst material of 0.5 M on Carbon paper achieved the maximum power density of 19.95 mWcm^-2 and current density of 28 mAcm^-2 at the voltage efficiency of 69.85%. Hence, the investigation would be beneficial to determine the suitable performance of two-phase flow configuration for redox flow battery with low-cost materials and to gain in-depth understanding of operation characteristics of a redox flow battery using hydrochloric acid as a reactant for new modeling of two-phase flow in cathode.

Keywords: Redox battery, energy storage, hydrochloric acid, catalyst synthesis.

Emily E. Ikhide

Abstract: Achieving economic development alongside environmental sustainability is a major priority of the global development agenda. This relationship between economic development and environmental quality is depicted by the Environmental Kuznets Curve hypothesis. Although there are several studies that have examined the validity or otherwise of the hypothesis, available evidence shows mixed and inconclusive results. In the case of Nigeria, there has also been no attempt to empirically estimate the turning point of the curve. Hence, this study examines the validity of the hypothesis in Nigeria, and estimates the turning point, based on yearly time series data from 1980 to 2016 and the Autoregressive Distributed Lag bound testing approach. The results confirm a long-run relationship between the series and provide evidence in support of the hypothesis in Nigeria. There is a positive sign between Gross Domestic Product (GDP) and CO₂ emissions, while a negative sign is found for the square of GDP. However, the linear term is bigger than the non-linear term, signifying that the environmental degradation effect of GDP growth is bigger than the environmental quality enhancement effect. Based on the results, the study recommends that the government develop policies to facilitate the transition from fossil-fuel and diversify the production base of the economy in order to mitigate the environmental effects of economic growth.

Keywords: Energy consumption, economic growth, CO2 emissions, EKC, Nigeria.

Manivanh Inthapakdy and Athikom Bangviwat*

Nitchanan Nantawong, Nishit Aman, Kasemsan Manomaiphiboon*, Peerapol Chankasem, Vanisa Surapipith and Awassada Phongphiphat

Abstract: This study characterizes aerosol optical depth (AOD) over Greater Bangkok (GBK) and nearby regions in Central Thailand (CT) using MODIS–Aqua AOD data for a period of 16 years (2003–2018). AOD and PM_2.5 show a linear relationship but its strength is small to fair, suggesting the contrast between the column–integrated and surface–level quantities. On a monthly scale, both GBK and CT show similar patterns for AOD variation (for both average and extreme). AOD in GBK is higher than that in CT due possibly to larger anthropogenic emissions. AOD is relatively low in the wet season due to the stronger wind and scavenging effect of rain. AOD peaks in March and October. The former peak is attributed to biomass burning for land clearing before wet–season cropping and more secondary aerosols induced by warm and humid conditions. The latter peak is due possibly to increased biomass burning in the late wet season for land clearing to support dry–season cropping since large irrigated areas are well present within CT. Dry–season AOD tends to intensify most and spread over large areas in February–April. Based on spatial correlation analysis, haze management for GBK in December and January needs to consider areas outside GBK. During February–April over the recent years, increased AOD in GBK, despite decreased biomass burning, is observed and likely to be induced by urbanization and economic growth but increased AOD in CT is thought or speculated to be more linked with unfavorable meteorological conditions. The developed multiple linear regression model to relate AOD in GBK and meteorology explains 43% of total variability in dry–season AOD. The important input meteorological variables remaining in the final regression include persistence, cloud cover, relative humidity, wind speed, and westerly wind. Persistence shows positive association with AOD, suggesting haze problems to be multi–day events.

Keywords: Air quality, urbanization, seasonality, spatial coherency, fires.