MRS Energy & Sustainability - Sustainable Energy and Environmental Materials

Sustainable Energy and Environmental Materials: An introduction
 

Guest Editors: Chun-Pu Liu, Han-Yi Chen
 

In recent decades, severe air pollution and greenhouse gas emissions resulting from fossil fuel use have accelerated alternative sustainable energy development and increased energy storage technology. Fuel cells are one of the most important sustainable energy technologies where only H2O is used to generate electricity by consuming H2 and O2/air. Today, H2 can be obtained by various methods, including thermal decomposition, thermochemical, electrolysis, electrochemical, photoelectrochemical, and biological methods. The direct conversion of chemicals into electrical energy via fuel cells has attracted significant attention, and the methanol oxidation reaction is of great interest to the development of high-performance direct methanol fuel cells. 
 

This collection presents several of these approaches to energy conversion via fuel cell, including size-selected Pt-graphene oxide nanoribbon composites as highly efficient fuel-cell anode photoelectrocatalysts for methanol oxidation reaction in an alkaline solution under visible light, and water splitting using the photoelectrochemical method as a cost-effective and environmentally friendly process for hydrogen production. Another contribution reports a feasible scheme to develop high-performance Sb-doped ZnO nanorods as photoelectrodes for photoelectrochemical water splitting.[1] In recent years, urea electrolysis has also received increasing attention as it can purify urea-contaminated wastewater to produce hydrogen fuel. Here, authors report that NiS2-reduced graphene oxide exhibits increased electrical conductivity and higher active surface area, thus enhancing the reaction kinetics of urea oxidation.[2]
 

Metals and alloys are important materials for industrialized societies, and many pyrometallurgical operations generate hazardous gaseous such as CO2 emissions. Therefore, decreasing the environmental footprint of the pyrometallurgical industry demands immediate attention. Greener reactants, renewable energies, and environmental impact mitigation strategies in pyrometallurgical processes are discussed in another contribution to this collection.[3] Recently, the reverse water–gas shift reaction has been proposed as a promising process to convert waste CO2 and H2 into valuable syngas, which can be used as precursors in the chemical industry. Authors demonstrate the decoupled reverse water–gas shift reaction by chemical looping using an earth‑abundant iron‑based oxygen carrier with high selectivity.[4]
 

Lithium-ion batteries (LIBs) are commonly used energy storage devices in portable electronic devices and electric vehicles. However, conventional LIBs cannot satisfy the demands of modern society for high-energy applications. Lithium-sulfur batteries are a promising next-generation energy storage system because of the S cathode with low cost and high theoretical energy density of 2600 Wh kg−1. However, polysulfide dissolution leads to poor cycling stability, low sulfur utilization, and poor rate performance, thus restricting practical applications. In another contribution, authors reveal a simple sol-gel method to prepare a Ti4O7 conductive metal oxide which is partially added to a lithium-sulfur battery cathode, resulting in a better rate capability and reversible cycling performance owing to its high electronic conductivity and surface adsorption of polysulfides. Conventional liquid electrolytes used in LIBs with highly flammable liquid characteristics raise battery safety issues. Therefore, conducting solid‑state electrolytes enables all‑solid‑state lithium batteries to exhibit excellent safety with high energy density. Authors demonstrate a unilateral structure combining the flexible poly(ethylene oxide) polymer with ceramic fillers (Li6.4La3Zr1.4Ta0.6O12) that exhibits well-inhibiting lithium dendrite growth.[5]
 

Although LIBs possess a long cycle life and excellent energy density, limited lithium resources present economic challenges. Therefore, sodium-ion batteries (SIBs) and zinc-ion batteries (ZIBs) have recently received great attention due to their low cost. Furthermore, using agricultural waste-derived carbons as electrode materials can allow low-cost and environmentally friendly electrodes for SIBs. A nitrogen-doped hard carbon synthesized from the agricultural waste of mushroom bags is used as a sustainable anode material for SIB application.[6] In addition, aqueous sodium-ion batteries (ASIBs) and aqueous zinc-ion batteries (AZIBs) possess the advantages of cost‑effectiveness and high safety. Authors introduce a novel material, NaMo0.05Ti1.95(PO4)3, as an anode for ASIBs, which exhibits high rate capability and long cycle life, demonstrating its potential for large-scale energy storage.[7] Authors present an overview of the recent developments and challenges in AZIB cathode materials, especially the mechanistic study and structural transformation regarding Zn intercalation/deintercalation chemistry.[8] 
 

Metal-organic frameworks (MOFs), known for their high surface area and tunable porosity, have attracted extensive attention in recent years. The carbon materials derived from MOFs have also been widely developed in energy storage and conversion, electrocatalysis, and other fields because of these properties. A review of preparation methods of MOFs and MOF-derived carbon materials is given in another contribution to the collection. Furthermore, novel nanocomposites composed of porous and water-stable MOF-808 crystals interconnected by electrically conductive CNT are reported here as a promising material for the negative electrodes in supercapacitors.[9]
 

These advanced works cover several topics related to sustainable energy and environmental materials, such as greener strategies in pyrometallurgical processes, materials for energy storage, energy conversion, and electrocatalysis/photoelectrocatalysis.

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References
[1] Y.-L. Hsiao, P.-C. Chen, K. Gupta, C.-C. Lai, Y.-C. Pu, C.-P. Liu, MRS Energy & Sustainability, 9, 19-27 (2022). https://doi.org/10.1557/s43581-022-00021-3
[2] T.H. Wu, J.J. Zhan, B.W. Hou, Z.T. Qiu, MRS Energy & Sustainability, 9, 324–331 (2022). https://doi.org/10.1557/s43581-022-00032-0
[3] J.-P. Harvey, W. Courchesne, M.D. Vo, K. Oishi, C. Robelin, U. Mahue, P. Leclerc, A. Al-Haiek, MRS Energy & Sustainability, 9, 212–247 (2022). https://doi.org/10.1557/s43581-022-00042-y
[4] W.-Z. Hung, Z.X. Law, D.-H. Tsai, B.-H. Chen, C.-H. Chen, H.-Y. Hsu, Y.-T. Pan, MRS Energy & Sustainability, 9, 342–349 (2022). https://doi.org/10.1557/s43581-022-00039-7
[5] P.-Y. Chen, R.-T. Kuo, T.-Y. Lin, MRS Energy & Sustainability, 9, 360–368 (2022). https://doi.org/10.1557/s43581-022-00045-9
[6] R. Muruganantham, Y.-X. Chiang, W.-R. Liu, MRS Energy & Sustainability, 9, 313–323 (2022). https://doi.org/10.1557/s43581-022-00025-z
[7] C.-Y. Wu, S.-C. Huang, J. Patra, C.-C. Lin, C.-S. Ni, J.-K. Chang, H.-Y. Chen, C.-Z. Lu, MRS Energy & Sustainability, 9, 350–359 (2022). https://doi.org/10.1557/s43581-022-00041-z
[8] S. Gull, H.-Y. Chen, MRS Energy & Sustainability, 9, 248–280 (2022). https://doi.org/10.1557/s43581-022-00044-w
[9] Y.-H. Chen, C.-H. Shen, T.-E. Chang, Y.-C. Wang, Y.-L. Chen, C.-W. Kung, MRS Energy & Sustainability, 9, 332–341 (2022). https://doi.org/10.1557/s43581-022-00034-y