Aqueous electrolyte‐based batteries have attracted increasing attention because of nonflammability, low cost, high power density, and environmental friendliness. However, the low energy density of aqueous lithium‐ion batteries caused by the narrow stable electrochemical window of water and electrode materials with low capacity severely limits their further development. In this regard, the development of metal anodes with high specific capacity shows excellent prospects. For example, metal zinc and aluminum anodes have high theoretical specific capacity, rich resources, and environmental friendliness, and can be used as promising anodes for high‐energy‐density aqueous rechargeable metal batteries. Unfortunately, metal anodes usually face balance issues with regard to stability and activity associated with dendrite growth and undesired side reactions in water‐based electrolytes, which is still a great challenge for aqueous metal batteries. In this review, various aqueous metal batteries including aqueous rechargeable metal batteries and aqueous metal–air batteries are summarized and highlighted. Recent advances in the design of high‐safety aqueous electrolytes and the strategies for metal anode protection are comprehensively reviewed. In addition, emerging challenges and some perspectives on the development of high‐energy‐density aqueous metal batteries are included.

Carbon is a simple, stable and popular element with many allotropes. The carbon family members include carbon dots, carbon nanotubes, carbon fibers, graphene, graphite, graphdiyne and hard carbon, etc. They can be divided into different dimensions, and their structures can be open and porous. Moreover, it is very interesting to dope them with other elements (metal or non‐metal) or hybridize them with other materials to form composites. The elemental and structural characteristics offer us to explore their applications in energy, environment, bioscience, medicine, electronics and others. Among them, energy storage and conversion are extremely attractive, as advances in this area may improve our life quality and environment. Some energy devices will be included herein, such as lithium‐ion batteries, lithium sulfur batteries, sodium‐ion batteries, potassium‐ion batteries, dual ion batteries, electrochemical capacitors, and others. Additionally, carbon‐based electrocatalysts are also studied in hydrogen evolution reaction and carbon dioxide reduction reaction. However, there are still many challenges in the design and preparation of electrode and electrocatalytic materials. The research related to carbon materials for energy storage and conversion is extremely active, and this has motivated us to contribute with a roadmap on ‘Carbon Materials in Energy Storage and Conversion’.

Energy storage and conversion have attained significant interest owing to its important applications that reduce COi emission through employing green energy. Sorne promising technologies are included metal air batteries, metal sulfur batteries, met al ion batteries, electrochemical ca pacitors, etc. Here, metal elements are involved with lithium, sodium, and magnesium For these devices, electrode materials are of importance to obtain high performance. Two dimensional (2D) materials are a large kind of layered structured materials with promising future as energy storage materials, which include graphene, black phosporus, MXenes , covalent organic frameworks ( COFs ), 2D oxides, 2D chalcogenides, and ot hers. Great progress has been achieved to go ahead for 2D materials in energy storage and conversion. More researchers will j oin in this res earch field. Under the background, it has motivated us to c ontribute with a roadmap on 'two dimensional materials for energy storage and conversion.

Serious challenges in energy and the environment require us to find solutions that use sustainable processes. There are many sustainable electrocatalytic processes that might provide the answers to the above-mentioned challenges, such as the oxygen reduction reaction (ORR), water splitting, the carbon dioxide reduction reaction (CO2RR), and the nitrogen reduction reaction (NRR). These reactions can enhance the value added by producing hydrogen energy through water splitting or convert useless CO2 and N2 into fuels and NH3. These electrocatalytic reactions can be driven by high-performance catalysts. Therefore, the exploration of novel electrocatalysts is one of the important electrocatalytic fields. In this paper, we aim to systematically discuss a variety of electrocatalysts used for sustainable processes and to give further insights into their status and associated challenges. We invited many famous research groups to write this roadmap with topics including platinum (Pt) and its alloys for ORR, oxides for ORR, chalcogenides for ORR, carbon-based hollow electrocatalysts for ORR, carbides for ORR, atomically dispersed Fe–N–C catalysts for ORR, metal-free catalysts for ORR, single-atom catalysts (SACs) for ORR, metal boride (MB) electrocatalysts for water splitting, transitional metal carbides (TMCs) for water splitting, transition metal (TM) phosphides for water splitting, oxides for water splitting, sulfides for water splitting, layered double hydroxides for water splitting, carbon-based electrocatalysts for water splitting, Ru-based electrocatalysts for water splitting, metal oxides for CO2RR, metal sulfides for CO2RR, metals for CO2RR, carbon for CO2RR, SACs for CO2RR, heterogeneous molecular catalysts for CO2RR, oxides for NRR, chalcogenides for NRR, C3N4 for NRR, SACs for NRR, etc. Their contributions enabled us to compile this 2020 roadmap on electrocatalysts for green catalytic processes and provide some suggestions for future researchers.

Ionogel-based chemoresistive humidity sensors have been successfully fabricated through ionothermal assembly of ionic liquids into a silica network, which exhibited superior humidity performances. Fast substantial impedance changes were observed with changing humidity for real-time monitoring of human breath.