Sustainable vitality storage and conversion applied sciences are crucial for addressing environmental and vitality crises brought on by the intensive use of fossil fuels [1], [2]. Accordingly, clear vitality applied sciences equivalent to water splitting, gasoline cells, and metallic–air batteries have attracted appreciable curiosity resulting from their excessive vitality effectivity and environmental sustainability [3], [4]. The effectivity and performance of those vitality programs 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 best electrocatalysts for oxygen discount response (ORR), which act as cathodes of gasoline cells and metal-air batteries because the reverse of OER [11]. Whereas these supplies successfully cut back activation vitality limitations of gradual electrochemical reactions, their excessive value and shortage hinder their practicality for widespread long-term business use in renewable vitality applied sciences [12]. In response to those limitations, porous nanostructured supplies shaped by assembling molecular precursors have emerged as promising electrocatalysts resulting from their novel options, together with giant inside floor areas and environment friendly molecular transport [13], [14], [15], [16], [17]. Amongst numerous porous supplies, aerogels (AG) stand out with distinctive physicochemical properties equivalent to giant 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 important consideration for his or her use as catalysts and catalyst helps in water electrolysis (WES). Particularly, AG-based catalysts provide a number of benefits for WES. First, they are often synthesized utilizing quite a lot 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 enticing, because it integrates the intrinsic properties of energetic supplies with an interconnected community of macro, meso, and micropores. This hierarchical porosity facilitates multidimensional electron and ion transport inside 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 offers quite a few energetic websites for redox reactions, which predominantly happen on the materials floor and interfaces. Lastly, due to versatile synthesis strategies and the usage of numerous constructing blocks, the energetic 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 provide distinctive mechanical energy, ultra-low density, and noteworthy stability underneath harsh situations. These distinctive properties have led to widespread adoption throughout numerous fields, vitality storage, biomedicine, thermal insulation, air pollution adsorption, and aerospace [19]. Because the first AG was developed in 1931 by Samuel Kistler utilizing a supercritical drying technique [20], AGs have considerably advanced by advances in synthesis strategies, which have launched numerous AG varieties and thus broadened their definition. For example, a nanoporous community of AG imparts a low dielectric fixed, wonderful thermal insulation, giant floor space, and excessive porosity, enabling purposes throughout chemistry, optics, electronics, and biology [22]. As well as, improved synthesis methods have additionally enabled the event of composite AGs incorporating carbon, polymers, metallic oxides, metal-organic frameworks, MXenes, chalcogenides, or nitrides [25]. These numerous composite AGs allow entry to not solely excessive ranges of mechanical stability but in addition a variety of purposeful properties, facilitating their utility 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 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 trade membrane electrolysis (1996). Following 1996, important developments have been made in AG-based electrode architectures by integrating nanomaterials and within the evolution of non-precious and hybrid metallic 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 data on AG synthesis methods, structural and electrochemical traits, integration with purposeful supplies, and mechanistic insights from computational approaches equivalent to density purposeful idea (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 supply 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 summary of assorted preparation methods (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 study the structural traits of AG-based electrodes (Part 4) and overview current research on AG purposes in HER, and OER, highlighting their function in enhancing catalytic effectivity and sturdiness (Part 5). Moreover, we discover the mixing of DFT as an important computational instrument that enhances experimental efforts by uncovering the molecular mechanisms of WES (Part 6). Lastly, we suggest future perspective and challenges in growing cost-effective, high-performance AG-based supplies for sustainable WES (Part 7).
