Vol. 2 No. 2 (2024)

All human activities are nothing more than the conversion and flow of energy, and energy flow processes that have irreversible effects on the Earth’s environment are of particular concern. Energy flow processes of interest are less often purely physical, and more often include complex chemical processes involving light, electricity, heat, and force, which are inevitably distributed in almost all human activities. Therefore, the optimization of these processes towards maximizing energy efficiency is inevitably the result of multi-physical and interdisciplinary collaborations, which will ultimately have a significant impact on the likelihood and schedule of achieving the goal of energy conservation and emission reduction. The authors of the articles in this issue, with creative thinking, rigorous arguments, and abundant data, have superbly illustrated the need for multiphysics and interdisciplinary synergy in clean energy science and technology from a wide range of perspectives.

Heteropolyacids can retain water in a proton exchange membrane to increase proton conductivity at high temperatures and low humidity; however, their high solubility in water leads to leaching, which limits their further application. Herein, we used phosphotungstic acid (HPW) and polydopamine (PDA) particles to prepare a water-insoluble PDA/HPW hybrid (PDW) via hydrothermal reaction. The amino groups of PDA in PDW chemically bonded to HPW and acted as an anchor for HPW. The proton conductivity of the sulfonated poly(ether ether ketone) (SPEEK) composite membrane containing 15wt% PDW (SPEEK/PDW-15) in liquid water was 0.052 S⸱cm^–1 at 25 ℃, which was 63% higher than that of the SPEEK control membrane (0.032 S⸱cm^–1). The SPEEK/PDW-15 composite membrane also showed stable proton conductivity during 80 days of testing while immersed in water.

Carbon monoxide (CO) is well recognized as one of the key intermediates for carbon dioxide (CO₂) electrolytic reduction to C₂₊ products, which has been a hot research field recently. Developing an efficient catalyst that focuses on achieving C-C coupling is highly important for the production of C₂₊ products. In the present work, we present a feasible approach via the combination of electrostatic assembly and the hydrothermal method of coupling silicon polyanions and copper salts to build an amorphous copper hybrid material wrapped in carbon-silica, denoted as CuO@C-SiO₂-X (where X means preparation temperature), as an efficient electrocatalyst for carbon monoxide reduction mainly to liquid C₂₊ products. The CuO@C-SiO₂-X catalyst demonstrated excellent electrocatalytic activity and selectivity, especially to C₂₊ liquid products with the highest Faradaic efficiency of 81.5%. Additionally, the catalyst showed good stability. The presence of carbon enhanced electronic conductivity, and the silica protected the amorphous CuO from aggregation into crystalline structures. The present work not only provides an efficient catalyst for CO electrocatalytic reduction to liquid C₂₊ chemicals but also offers a protocol for building Cu-based catalysts with high selectivity to C₂₊ products in CO reduction.

The screening of working fluids is one of the key components in the study of power generation systems utilizing low-temperature waste heat. However, the variety of working fluids and their complex composition increase the difficulty of screening working fluids. In this study, a screening strategy for working fluids was developed from the perspective of the thermodynamic physical properties of working fluids. A comparative ideal gas heat capacity via the reduced ideal gas heat capacity factor (RCF) was proposed to characterize the dry and wet properties of working fluids, where RCF > 1 indicated a dry working fluid and RCF < 1 indicated a wet working fluid. A three-step screening strategy was developed for working fluid screening for organic Rankine cycles (ORCs). The strategy comprised basic physical property analysis of working fluids, research on dry and wet properties, and quantum chemical analysis. By comparing the RCF calculation result of 23 selected working fluid with values from the literature, the relative deviations of the data were less than 6.64% overall, indicating that the calculation result of the RCFs is reliable. The selection strategy explains the mechanism of working fluid selection in ORC systems from both micro- and macro-perspectives, laying a foundation for the study of structure-activity relationships in working fluids for ORCs.

The process efficiency and energy efficiency of extrusion equipment emerge as pivotal challenges constraining the development of the polymer extrusion industry. This article presents a new principle of polymeric field synergy to guide the solution to the low mixing efficiency and energy utilization efficiency of traditional extrusion equipment. Finite element analysis was conducted on four novel unconventional screw configurations and compared with the traditional single-thread screw. Results revealed that more complicated melt flow patterns generated in the modified novel screw configurations enhanced the stretching deformation or helical flow. The stretching or helical flows to varying degrees during the melt extrusion process thereby improved the mixing and heat transport efficiency. Among them, helical flow induced by the Maddock element exhibited the most significant impact on stretching flow and ductile deformation in the flow field. Simultaneously, the helical flow caused radial motion of the internal material, significantly promoting the synergy between the velocity field, velocity gradient field, and temperature gradient field. This enhanced radial heat and mass transport efficiency within the screw channel, subsequently improving the overall operational efficiency of the equipment. The results of the finite element analysis have substantiated the scientific validity of the polymeric field synergy principle.

The energy derived from fossil fuels significantly contributes to global warming (GW), accounting for over 75% of global greenhouse gas emissions and approximately 90% of all carbon dioxide emissions. It is crucial to rely on alternative energy from renewable energy (RE) to mitigate carbon emissions in the energy sector. Renewable energy sources have the potential to eliminate carbon from 90% of electricity generation by 2050, greatly reducing carbon emissions and helping alleviate the impacts of GW. By emphasizing the concept of zero emissions, the future of renewable energy becomes promising, with the possibility of replacing fossil fuels and limiting global temperature rise to 1.5 ℃ by 2050. In this article, renewable energy technologies and their role in various areas to combat GW are explored, examining trends and successes in supporting renewable energy policies and exploring available options to mitigate the effects of climate change and achieve a clean energy future. Moreover, RE offers a clean and sustainable alternative to fossil fuels, reducing reliance on them and minimizing greenhouse gas emissions. This paper also highlights the efforts of leading countries, including China, the United States, India, and Germany, in developing and utilizing renewable energy. These countries’ renewable energy strategies reflect their commitment to combat global warming and reduce harmful emissions for the well-being of present and future generations.

The pulp and paper industry is one of the most energy-intensive industries. Achieving net-zero emissions in this industry is crucial for mitigating global warming and reducing environmental pollution. The article entitled “Country-specific net-zero strategies of the pulp and paper industry,” published in Nature, addressed this issue. Through an in-depth analysis of the historical emission data of the pulp and paper industry in 30 major countries, a series of country-specific net-zero strategies were proposed. This commentary reviewed the main content and views of that article, and the rigor and applicability of its methods are discussed. Then, the potential impacts of economic trade-offs, resource endowments, and technological advancements on the net-zero strategies of the pulp and paper industry in various countries are further considered.

The separation of propylene (C₃H₆) and propane (C₃H₈) is very costly due to similar physical-chemical properties and has been listed as one of the seven chemical separations to change the world. High-purity C₃H₆ is an important raw material to produce polypropylene and acrylonitrile. However, C₃H₈ is produced as a by-product in the production process of C₃H₆, which has a similar structure and boiling point as those of C₃H₆. Traditionally, the separation of C₃H₆ and C₃H₈ by distillation has high energy consumption and an unremarkable separation effect. Therefore, there is an urgent need to develop more energy-saving and efficient methods for the separation of C₃H₆ and C₃H₈.