Development of affordable electrocatalysts for both oxygen reduction and evolution reactions (ORR/OER) has received great interest due to their importance in metal-air batteries and regenerative fuel cells. We develop the...

Low-cost sensors (LCS) have been increasingly deployed to monitor PM2.5 concentrations. More than 1500 LCS have been installed in Thailand to increase public awareness of air quality. However, performance of these sensors has not been systematically investigated. In this study, PM2.5 LCS were co-located next to a PM2.5 federal equivalent method (FEM) reference instrument at three Thai locations—in the north, center and northeast. We evaluated the performance of a PM2.5 LCS (PMS7003, Plantower) to understand the key factors affecting performance, including emission sources, relative humidity, temperature and PM2.5 concentration. Low PM concentration and high humidity levels had a significant impact on performance. Sensors in a high traffic emission area showed low correlation. The unadjusted PM2.5 LCS performance varied with locations. Errors were mainly observed at low concentrations. They significantly underestimated concentrations in congested urban environments. After calibration, accuracy was improved with multiple regression models. The performance of sensors only at Chiang Mai (CM) during the dry season and Ubon Ratchathani (URT) during the dry and wet seasons were acceptable with coefficient of variation: 5.8 ± 4.7–6.8 ± 5.0%, slope: 0.829–0.945, intercept: 1.12–5.49 µg/m3, R2: 0.880–0.934 and RMSE: 4.3–5.1 µg/m3. In the congested area in Bangkok (BKK), they underestimated concentrations of small particles.

This research studied the possibility of converting water hyacinth biomass into the porous non-precious oxygen reduction reaction (ORR) electrocatalyst using a simple, low cost and scalable autogenic pressure method. The electrocatalyst was prepared by thermally annealing water hyacinth root contained ZnCl2 at 700oC under autogenic pressure conditions. The phase of the catalyst was the mixture of carbon and metal oxide. In addition, rough surface morphology and high porosity were clearly observed using scanning electron microscope. The synthesized catalyst was then determined the ORR performance by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques under O2 saturated KOH solution. The ORR performance increased as the catalyst loading was increased and the optimum catalyst loading was found to be 1.5 mg/cm2 which generated the Eonset and E1/2 value of 0.93 V and 0.80 V vs. RHE, respectively. Furthermore, the E1/2 value of the synthesized catalyst was 230 and 130 mV greater than the catalyst synthesized without ZnCl2 and commercial carbon (VXC-72R). ORR durability study suggested that the prepared catalyst was durable to operate ORR for 5000 cycles in alkaline media. These results suggested that the autogenic pressure conditions would be a promising technique to prepare highly active and durable biomass derived ORR electrocatalyst.

Discovering a high performance, durable, and cost-effective oxygen reduction reaction (ORR) electrocatalyst is a key strategy for widespread use of the high efficiency and environmentally friendly fuel cell and metal-air battery technologies. Herein, we fabricate a high performance and durable metal free N and S dual-doped mesoporous carbon nanostructure (NS-VXC) ORR catalyst using solid state thermolysis at 700 °C for 1 h. The fabricated catalyst exhibits nanocarbon aggregated chain-like morphology with a high surface area and mesoporous structure. The amount of N and S dopants embedded in mesoporous carbon nanostructure is found to be 3.2 and 1.1%, respectively which significantly attribute to the synergistic effect of spin and charge density leading to not only superior ORR performance but excellent durability in the alkaline environment as well. Rotating ring disk electrode analysis reveals the codoped NS-VXC catalyst possesses a direct 4-electron transfer number pathway with extremely low peroxide intermediate content. Compared to the benchmark Pt/C catalyst, the fabricated NS-VXC catalyst generated 10 mV ORR performance outperform and negligible performance degradation after the 10,000 ORR cycling test. These results suggest that an innovative solid state thermolysis methodology can be a powerful nanomaterial fabrication technique to generate high performance and excellent durability electrocatalyst for green energy applications.