Sustainable power storage and conversion applied sciences are crucial for addressing environmental and power crises attributable to the intensive use of fossil fuels [1], [2]. Accordingly, clear power applied sciences equivalent to water splitting, gas cells, and steel–air batteries have attracted appreciable curiosity resulting from their excessive power effectivity and environmental sustainability [3], [4]. The effectivity and performance of those power methods are primarily dictated by basic electrochemical reactions, together with hydrogen evolution (HER), and oxygen evolution (OER) [5], [6], [7], [8].
The benchmark electrocatalysts within the electrochemical water-splitting are Pt for HER and Ru/Ir primarily based supplies for OER [9], [10]. These catalysts are used on the anode and cathode, respectively, in water-splitting cells. Moreover, Pt and its alloys are acknowledged as the simplest electrocatalysts for oxygen discount response (ORR), which act as cathodes of gas cells and metal-air batteries because the reverse of OER [11]. Whereas these supplies successfully scale back activation power limitations of sluggish electrochemical reactions, their excessive value and shortage hinder their practicality for widespread long-term business use in renewable power applied sciences [12]. In response to those limitations, porous nanostructured supplies fashioned by assembling molecular precursors have emerged as promising electrocatalysts resulting from their novel options, together with massive inner floor areas and environment friendly molecular transport [13], [14], [15], [16], [17]. Amongst varied porous supplies, aerogels (AG) stand out with distinctive physicochemical properties equivalent to massive floor areas (as much as 1000 m2 g−1), low thermal conductivity, open meso- and macro-porous constructions, tunable floor chemistry, low acoustic propagation velocity, and ultra-light density (roughly 1.2 × 10−4 g cm−3) [18], [19], [20]. These traits have attracted vital consideration for his or her use as catalysts and catalyst helps in water electrolysis (WES). Particularly, AG-based catalysts supply a number of benefits for WES. First, they are often synthesized utilizing a wide range of constructing blocks or precursors with tailor-made properties, enabling enhanced efficiency and focused catalytic functionalities. Second, the self-supporting porous construction of AG monoliths is especially engaging, because it integrates the intrinsic properties of lively supplies with an interconnected community of macro, meso, and micropores. This hierarchical porosity facilitates multidimensional electron and ion transport throughout the 3D community, thereby enhancing catalytic effectivity [21], [22]. Moreover, this monolithic porous construction usually minimizes inhomogeneous agglomeration and restacking points generally noticed in low-dimensional catalysts, serving to to protect floor space and catalytic exercise throughout WES [23], [24], [25]. Third, the excessive floor space of AG gives quite a few lively websites for redox reactions, which predominantly happen on the materials floor and interfaces. Lastly, due to versatile synthesis strategies and using varied constructing blocks, the lively catalytic websites in AGs could be simply tuned by modifying their floor chemistry. Equally, foams-which share many properties with AGs-are additionally broadly studied [26], [27].
Constructing on these promising options, rising AG-based supplies, typically known as one of many ‘shock supplies’ within the 21st century, can supply distinctive mechanical power, ultra-low density, and memorable stability underneath harsh circumstances. These distinctive properties have led to widespread adoption throughout varied fields, power storage, biomedicine, thermal insulation, air pollution adsorption, and aerospace [19]. For the reason that first AG was developed in 1931 by Samuel Kistler utilizing a supercritical drying methodology [20], AGs have considerably developed by way of advances in synthesis strategies, which have launched numerous AG varieties and thus broadened their definition. As an example, a nanoporous community of AG imparts a low dielectric fixed, wonderful thermal insulation, massive floor space, and excessive porosity, enabling functions throughout chemistry, optics, electronics, and biology [22]. As well as, improved synthesis strategies have additionally enabled the event of composite AGs incorporating carbon, polymers, steel oxides, metal-organic frameworks, MXenes, chalcogenides, or nitrides [25]. These varied composite AGs allow entry to not solely excessive ranges of mechanical stability but in addition a variety of practical properties, facilitating their software in a rising variety of fields [27], [28], [29].
Benefiting from the advances in AG supplies, from the 21st century, AGs have emerged as a central focus within the WES that made the historic improvement (Fig. 1 (A)) by way of its discovery in 1789, industrially alkaline electrolysis (1888), asbestos membranes (1890), metal-based electrocatalysts (1900), large-scale electrolyzers (1939), pressurized electrolyzers (1948), and Nafion-based proton alternate membrane electrolysis (1996). Following 1996, vital developments have been made in AG-based electrode architectures by integrating nanomaterials and within the evolution of non-precious and hybrid steel catalysts, leading to improved catalytic effectivity and broadening the scope of WES applied sciences [13], [14], [23]. Regardless of this progress, a complete overview specializing in AG-based supplies in WES continues to be missing. Particularly, there’s a must consolidate information on AG synthesis methods, structural and electrochemical traits, integration with practical supplies, and mechanistic insights from computational approaches equivalent to density practical concept (DFT), which might spotlight how rational structural engineering of AG-based electrodes is translated into enhanced electrocatalytic efficiency (Fig. 1 (B)).
To fill this hole, subsequently, this overview article goals to offer an in-depth evaluation of AG-based electrocatalysts for sustainable WES. This overview begins by outlining the crucial parameters influencing electrocatalytic efficiency (Part 2), adopted by an outline of assorted preparation strategies (Part 3), together with sol–gel strategies, meeting strategies, template-assisted strategies, emulsion strategies, 3D printing strategies, electrospinning strategies, and hydrothermal and freeze-drying strategies. Subsequently, we look at the structural traits of AG-based electrodes (Part 4) and overview latest research on AG functions in HER, and OER, highlighting their function in enhancing catalytic effectivity and sturdiness (Part 5). Moreover, we discover the combination of DFT as an important computational device that enhances experimental efforts by uncovering the molecular mechanisms of WES (Part 6). Lastly, we suggest future perspective and challenges in creating cost-effective, high-performance AG-based supplies for sustainable WES (Part 7).
