Strategy and Methods for Carbon Emission Mitigation during Construction of Rail Transit.

The rail transit construction process produces a large quantity of carbon emission. The carbon emission could be divided into two sources, including direct carbon emission from the construction process and indirect carbon emission by raw material utilization. With the promotion of China National carbon peaking and carbon neutrality goals, it is an industry trend for the rail transit construction company to reduce carbon emission during the construction event. This study provides a detailed overview of the possible carbon emission process and carbon mitigation process during the rail transit construction event and puts forward preliminary carbon mitigation suggestions and strategy for the rail transit construction process. The predominant carbon emission section during rail transit construction is the raw material (including the steel, cement, concrete, tunnel segment), electricity, and fuel consumption during construction. It is suggested that the rail transit construction process could achieve carbon emission mitigation from the following prospects: make careful plans for the raw material selection (such as using recycled concrete, recycled steel, and so forth), improve the construction process to reduce energy waste, and optimize the equipment selection during the mechanical and electrical installment process. By this, the carbon emission could be mitigated during the rail transit construction.

Microdrop-confined synthesis and regulation of porous hollow Ir-based catalysts for the mass transfer-enhanced electrolysis of pure water.

Maximally exploiting the active sites of iridium catalysts is essential for building low-cost proton exchange membrane (PEM) electrolyzers for green H2 production. Herein, we report a novel microdrop-confined fusion/blasting (MCFB) strategy for fabricating porous hollow IrO1-x microspheres (IrO1-x-PHM) by introducing explosive gas mediators from a NaNO3/glucose mixture. Moreover, the developed MCFB strategy is demonstrated to be general for synthesizing a series of Ir-based composites, including Ir-Cu, Ir-Ru, Ir-Pt, Ir-Rh, Ir-Pd, and Ir-Cu-Pd and other noble metals such as Rh, Ru, and Pt. The hollow structures can be regulated using different organics with NaNO3. The assembled PEM electrolyzer with IrO1-x-PHM as the anode catalyst (0.5 mg/cm2) displays an impressive polarization voltage of 1.593 and 1.726 V at current densities of 1 and 2A/cm2, respectively, outperforming commercial IrOx catalysts and most of the ever-reported iridium catalysts with such low catalyst loading. More importantly, the breakdown of the polarization loss indicates that the improved performance is due to the facilitated mass transport induced by the hollowness. This study offers a versatile platform for fabricating efficient Ir-based catalysts for PEM electrolyzers and beyond.