Peera Shaik Gouse, Byun Myunghwan
Natural Science Research Institute, College of Natural Sciences, Keimyung University, 1095 Dalgubeol-daero, Daegu 42601, Republic of Korea.
Department of Advanced Materials Engineering, College of Engineering, Keimyung University, 1095 Dalgubeol-daero, Daegu 42601, Republic of Korea.
Gels. 2025 Jun 21;11(7):479. doi: 10.3390/gels11070479.
Efficient electrocatalysts for the oxygen reduction reaction (ORR) are essential for numerous energy storage and conversion systems, including zinc-air batteries and fuel cells. Cutting-edge Pt/C catalysts remain the most efficient ORR catalysts to date; however, their high cost and inadequate stability impede their use in commercial devices. Recently, transition metal-based electrocatalysts are being pursued as ideal alternatives for cost-effective and efficient materials with a promising future. This review provides an in-depth analysis of the principles, synthesis, and electrocatalytic assessment of noble metal and transition metal-based catalysts derived from diverse gel precursors, including hydrogels, aerogels, xerogels, metal-organic gels, and metal aerogels. Electrocatalysts derived from gel precursors have garnered significant interest due to their superior physicochemical properties, including an exceptionally high surface area, adjustable porosity, adaptability, and scalability. Catalysts obtained from gel precursors offer numerous advantages over conventional catalyst synthesis methods, including the complete utilization of precursors, precise control over surface area and porosity, and uniform distribution of ORR active sites. Among the various types, metal aerogels are distinguished as the superior catalysts, exceeding the Department of Energy's (DoE) 2025 targets for the mass and specific activities of ORR catalysts. In contrast, hydrogel- and aerogel-derived catalysts excel in terms of ORR activity, specific surface area, and the potential to incorporate high loadings of single-atom catalysts composed of transition metals. Ultimately, we unequivocally categorized the electrocatalysts into high-, moderate-, and low-performance tiers, identifying the most promising catalyst candidate within each gel classification. Concluding insights, future outlooks, and recommendations were provided for the advancement of cost-effective, scalable electrocatalysts derived from gels for fuel cells and zinc-air batteries.
用于氧还原反应（ORR）的高效电催化剂对于众多能量存储和转换系统至关重要，包括锌空气电池和燃料电池。前沿的Pt/C催化剂至今仍是最有效的ORR催化剂；然而，其高成本和稳定性不足阻碍了它们在商业设备中的应用。最近，基于过渡金属的电催化剂正被视为具有成本效益且高效的理想替代材料，前景广阔。本综述深入分析了源自多种凝胶前驱体（包括水凝胶、气凝胶、干凝胶、金属有机凝胶和金属气凝胶）的贵金属和过渡金属基催化剂的原理、合成及电催化评估。源自凝胶前驱体的电催化剂因其优异的物理化学性质而备受关注，这些性质包括极高的表面积、可调节的孔隙率、适应性和可扩展性。与传统催化剂合成方法相比，由凝胶前驱体制备的催化剂具有诸多优势，包括前驱体的完全利用、对表面积和孔隙率的精确控制以及ORR活性位点的均匀分布。在各种类型中，金属气凝胶被视为 superior催化剂，超过了美国能源部（DoE）对ORR催化剂质量和比活性的2025年目标。相比之下，水凝胶和气凝胶衍生的催化剂在ORR活性、比表面积以及掺入由过渡金属组成的高负载单原子催化剂的潜力方面表现出色。最终，我们明确地将电催化剂分为高性能、中等性能和低性能三个等级，确定了每种凝胶类别中最有前途的催化剂候选物。为推进用于燃料电池和锌空气电池的具有成本效益、可扩展的凝胶衍生电催化剂，提供了总结性见解、未来展望和建议。
