Geopolymer is a porous inorganic material with a three-dimensional mesh structure, good mechanical properties, a simple preparation process (no sintering) and a low economic cost, and it is environmentally friendly. Geopolymer concrete has been widely used in the construction field, and many other studies have revealed that geopolymer will become one of the most promising inorganic materials with unique structure and properties. This paper provides a review of the development and current status of geopolymers and briefly explains the effects of material proportioning, experimental factors and activators on geopolymer performance. Because of the advantages of high specific surface area and high porosity, geopolymers could be used as adsorbent materials. This paper summarizes the research progresses of the adsorption of metal cations, anions, dyes, and gases by geopolymers, which emphasizes the geopolymer membranes in adsorption, and discusses the challenges and opportunities for the development of more efficient, sustainable and practical adsorption protocols.

Bipolar membranes, a new type of composite ion exchange membrane, contain an anion exchange layer, a cation exchange layer and an interface layer. The interface layer or junction is the connection between the anion and cation exchange layers. Water is dissociated into protons and hydroxide ions at the junction, which provides solutions to many challenges in the chemical, environmental and energy fields. By combining bipolar membranes with electrodialysis technology, acids and bases could be produced with low cost and high efficiency. The interface layer or junction of bipolar membranes (BPMs) is the connection between the anion and cation exchange layers, which the membrane and interface layer modification are vital for improving the performance of BPMs. This paper reviews the effect of modification of a bipolar membrane interface layer on water dissociation efficiency and voltage across the membrane, which divides into three aspects: organic materials, inorganic materials and newly designed materials with multiple components. The structure of the interface layer is also introduced on the performance of bipolar membranes. In addition, the remainder of this review discusses the challenges and opportunities for the development of more efficient, sustainable and practical bipolar membranes.

Non-firing functional oxide materials are attracting significant interest due to their suitability for a wide range of applications, particularly in thermal, electrical, and architectural fields. These materials, which range from natural to synthetic forms, offer a diverse range of properties. While oxides are generally known for their high mechanical strength, temperature resistance, and cost-effectiveness, traditional oxide processing often requires energy-intensive and environmentally unfriendly high-temperature sintering. Therefore, the investigation of energy-efficient non-firing mechanisms for oxides is not only beneficial but crucial. This paper reviews the advancements in non-firing mechanisms, with a focus on material selection, synthesis processes, and potential applications. Special attention is given to non-firing forms such as silica-based and geopolymer materials, which are prepared using low-energy acid-base reactions with either natural or synthetic silica-alumina sources. The review also encapsulates the challenges and solutions associated with these sustainable, non-firing oxide materials. Graphical Abstract

An electrochemical CO₂ reduction reaction (CO₂RR) is an effective way to reduce greenhouse gases by converting CO₂ into high-value-added chemical products using electricity generated from renewable energy. In this paper, a Cu₂O spherical catalyst was prepared by ascorbic acid reduction. The precipitated Cu-Ag spherical catalyst (P-CuO-Ag) was successfully prepared by calcining Cu₂O-Ag with the introduction of an Ag component as the substrate. During the electrochemical reduction of CO₂, the FE of the P-CuO-Ag catalyst for C₂H₄ at a potential of −1.1 V vs. RHE was as high as 39.8%, which was nearly twice that of the CuO catalyst, while the local current density J_C2H4 for C₂H₄ reached 6 mA cm⁻². The incorporation of Ag gives the spherical CuO catalyst higher electrochemical activity and better kinetic performance than the catalyst without Ag.

Closed-loop process with HNO ₃ /H ₂ O ₂ selective leaching and bipolar membrane electrodialysis (BMED) for hazard-free LiFePO ₄ battery recycling, converting HNO ₃ to safe reagent.