Pd is well-known for its remarkable capacity for hydrogen absorption/adsorption, and is broadly employed as a primary catalyst for the low-temperature reduction of automobile pollutants, hydrogenation reactions, hydrogen purification, petroleum cracking, and a wide range of electrochemical applications. This review has detailed and compared a number of methods for the synthesis of Pd-based nanomaterials, as well as the impacts of the dimensions, morphologies, and compositions toward various electrochemical applications. The fabrication methods described include physical synthesis techniques, hydrothermal methods, electrochemical deposition, and other methods, such as electroless deposition, microemulsions, and photochemically assisted synthesis. Section 3 discussed the chemical and catalytic properties of Pd and Pd-based nanomaterials for electrochemical purposes, including fuel cells, hydrogen purification and storage, gas sensors, biosensors, capacitors, and the degradation of pollutants.

The design and implementation of high-performance Pd-based nanomaterials are anticipated to grow considerably over the next decade. With increasing environmental concerns and the accelerated depletion of fossil fuels, there will be a significant demand for the development of advanced technologies for environmental remediation, as well as for the production of alternative energy conversion and storage devices. In the biomedical sector, the increasing need for point-of-care, real-time quantitative detection and monitoring will drive the emergence of innovative devices. However, a number of challenges remain to be resolved prior to the broad commercial application of Pd-based nanomaterials.

The primary drawback of Pd, much like platinum, is its exorbitant cost. Over the past several years, the price of Pd has increased and is expected to continue to rise as interest in this material expands. Because of this, there is an urgent requirement for the design of advanced catalysts to reduce the required amount of noble metals, while increasing their activity and stability. Issues to consider in the creation of novel Pd-based nanomaterials encompass (i) size control—to achieve optimal electrochemically active sites, (ii) shape control—to better understand growth mechanisms to effectively tailor the geometries of complex catalysts, (iii) control of high-index facets—for improved catalytic activity, (iv) optimization of bimetallic and trimetallic compositions and architectures—to enhance activity and stability, (v) establishment of the fundamental correlations between composition, structure, and reactivity of Pd nanomaterials—to create highly efficient catalysts by design, (vi) discovery of new substrate materials with high conductivity, chemical and mechanical stability, and surface area, and (vii) enabling the uniform distribution of Pd-based catalysts on support materials—to further improve efficiency.

The shape, size, architecture, composition, and microstructure of Pd-based nanocomposites are the key parameters in the determination and enhancement of their functionality and potential applications. The physical and chemical properties of Pd may be specifically tuned by controlling one or more of the aforementioned parameters. We are hopeful that this review has provided a practical framework to facilitate the emergence of innovations to address the challenges that currently impede the incorporation of Pd nanomaterials in various electrochemical applications, and demarcated the requirements for future development. Further advances in innovative synthesis techniques will undoubtedly lead to the discovery of additional unique properties of Pd-based nanomaterials, and subsequently to applications that will continue to benefit industry, the environment, and society at large.