ABSTRACT
Herein, a type of Fe, N-codoped carbon electrocatalyst (FeNx /C, Fe-N-BCNT#BP) containing bamboo carbon nanotubes and displaying bifunctional high catalytic efficiency for both oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR) is reported. It shows high electrocatalytic activity and stability for both the ORR process with onset potential of 1.03 VRHE in alkaline and the CO2RR to CO with high faradic efficiency up to 90% and selectivity of about 100% at low overpotential of 0.49 V. For CO2RR to CO, it is revealed that Fe3 C is active but the activity of FeNx centers is lower than that of C-N-based centers, contrary with that observed for ORR. Due to its low cost and high electrocatalytic performance for these two reduction reactions, the obtained catalyst is very promising for extensive application in future. The revealed huge activity difference of the same types of active sites for different reactions can efficiently guide the synthesis of advanced materials with multifunction.
ABSTRACT
The measurement of eco-efficiency is an important tool to evaluate the level of urban sustainable development. Therefore; improving urban eco-efficiency in the lower reaches of the Yellow River ensures the implementation of ecological protection and high-quality development strategies in the Yellow River Basin. In this study; the dynamic changes of urban eco-efficiency and spatiotemporal differences in the lower reaches of the Yellow River were investigated using the Super-SBM (Super-Slack measure model) model with undesirable outputs and standard deviation ellipse. The STIRPAT (Stochastic Impacts by Regression Population; Affluence and Technology) model was introduced to analyze the factors affecting the change in urban eco-efficiency. The results showed that the overall urban eco-efficiency in the lower reaches of the Yellow River has not reached the optimal level. The overall eco-efficiency in the lower reaches of the Yellow River in Shandong Province was higher than that in Henan Province but the gap is narrowing. The spatial differentiation of urban eco-efficiency in the lower reaches of the Yellow River showed the following trends: "blooming in the middle and reverse development at both ends" in the high-value area and gradual decrease in the low-value area. From 2007 to 2018; a direction was notable with respect to the development of urban eco-efficiency in the lower reaches of the Yellow River; with the centripetal force weakening. Although the mean center of urban eco-efficiency located in Shandong Province; it notably shifted to the west during the study period. In terms of driving factors; affluence and technological progress play positive roles in driving eco-efficiency; while investment intensity; industrial structure; and foreign investment intensity hindered the optimization and improvement of urban eco-efficiency in the lower reaches of the Yellow River. The results of this study show that urban eco-efficiency in the lower reaches of the Yellow River is improving; but the regional coordination is poor. The main methods promoting the sustainable development in the study area include changing the mode of extensive investments and the introduction of foreign capital; which improve the energy efficiency and promote faster and better economic development.