Recent progress in the fabrication of free-standing three-dimensional nanoporous metals: a review

Free-standing three-dimensional nanoporous metals (3D-NPM), a new type of advanced functional materials, are widely used in the fields of catalysis, sensing, energy storage, and conversion due to their large specific surface area, high conductivity, and unique catalytic performance. The efficient and large-scale preparation of 3D-NPM has always been a key issue in this field. There are two traditional fabrication methods for 3D-NPM: the dealloying and the template method. However, to meet the rapidly growing demand for 3D-NPM, many modification strategies to traditional methods and various novel fabrication approaches have been proposed, such as vacuum dealloying, molten metal dealloying, direct reduction, and redox process. In this work, we mainly systematically summarize the principles, advantages and disadvantages, and key influence factors of these fabrication methods, especially for the recently proposed novel fabrication methods. Furthermore, a prospect for the future development and main bottlenecks of 3D-NPM have also been proposed.