Climate change has become one of the greatest challenges to mankind in the 21st century as witnessed by the exponential growth of greenhouse gas emission and catastrophic climate events happening around the world. Materials Science and Engineering provides us with the opportunity to contribute to solving this challenge by modulating the structure-performance relation of materials. In this dissertation, I focus on one specific type of material systems, namely nanoporous metals which find wide applications in energy conversion and storage, and study their structure-performance relations towards various catalytic reactions including CO2 reduction, O2 evolution and H2 generation. In doing so, I aim to address two specific problems: (1) The traditional synthesis routes to nanoporous metals have limitations such as use of extreme environment, poor capability to create air- and water-sensitive nanoporous metals, and limited engineering approach towards controlling the structure of nanoporous metals in terms of size and composition; and (2) In many cases, the as-dealloyed nanoporous metals are not yet suitable for use as catalysts since their structure needs optimization. In the first part of this dissertation, I address problem (1) by introducing several alternative dealloying routes, namely synthesis of noble nanoporous metals such as nanoporous gold under mild conditions by engineering the reaction pathway, and synthesis of more chemically reactive nanoporous metals including nanoporous zinc and nanoporous magnesium by engineering the dealloying condition. Furthermore, I modulate the structure of nanoporous metals by combining dealloying with additive manufacturing to create robust, multiscale architecture with tunable compositions. In the second part of this dissertation, I address problem (2) by first understanding how the structure of dealloyed nanoporous metals can affect the performance of catalytic reactions. I find that the structure size, namely the bulk dimension of a catalyst, is governing the interplay between reaction rate and selectivity during CO2 reduction. The structure size is also critical towards improving the reaction rate and yield during metal hydrolysis, since the H2 generation performance in bulk materials is diminished by the self-blocking surface passive film. In terms of composition effect, my studies using nanoporous Ni-Fe-Mn ternary alloys with varying compositions show that there exist an optimal Ni/Fe ratio (Ni/Fe = 2) which exhibits optimal activity towards O2 evolution. Next, based on these findings on the structure-performance relations, I propose approaches to engineer the structure of dealloyed nanoporous metals towards optimal catalytic performance: (i) The multiscale architecture, as well as the structure size within each hierarchy can be manipulated by the design flexibility of additive manufacturing and dealloying; and (ii) The exploration of vast composition space can be accelerated by processing of additive manufacturing and dealloying, combined with high-throughput electrochemistry.