Meeting the current needs for easier, more precise and faster analyses that also follow the principles of green analytical chemistry requires novel analytical chemistry strategies. Since the appearance in this century of the first device based on a paper platform, many studies have been presented in the literature, providing a wide range of designs and possibilities for the application of paper platforms to electroanalytical systems. This Review gives an overview of the field and can pave the way for the future development of electrochemical paper‐based analytical devices. We also present a critical point of view regarding what has been investigated and developed and what is still missing. This Review discusses the efforts made in the field related to important topics such as the choice of the paper substrate, the device construction process, the characterization of the device, and applications in different areas. In this way, we indicate some steps necessary for optimizing the design of the devices, with a focus on multidisciplinary collaborations that could move entire systems from the bench of the laboratory to the field.

The increasing global needs for clean and renewable energy have fostered the design of new and highly efficient materials for fuel cells applications. In this work, Pd-M (M = Pd, Cu, Pt) and Pt nanoparticles were prepared by a green synthesis method. The carbon-supported nanoparticles were evaluated as electrocatalysts for the oxygen reduction reaction (ORR) in alkaline medium. A comprehensive electronic and structural characterization of these materials was achieved using X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Their electrochemical properties were investigated by cyclic voltammetry, while their activities for the ORR were characterized using steady-state polarization experiments. The results revealed that the bimetallic nanoparticles consist of highly crystalline nanoalloys with size around 5 nm, in which the charge transfer involving Pd and M atoms affects the activity of the electrocatalysts. Additionally, the samples with higher ORR activity are those whose d-band center is closer to the Fermi level.

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Owing to their versatility and unique characteristics, graphene‐based materials have been used extensively for the development of electrochemical sensors and biosensors. The key to the maximum potential of these materials is the understanding of the role their structure plays in their modification processes. Herein, we summarize some structural characteristics of graphene oxide (GO) and reduced graphene oxide (rGO) and explore different surface modification methods for electrochemical sensing applications. surveyed the most recent applications of these materials as (bio)sensors, particularly for environmental monitoring and health‐related applications, such as quantification of biomarkers and metabolites and detection of cancer cells. The low detection limits, selectivity toward target molecules, and robustness of GO‐ and rGO‐based electrodes render them critical materials for the preparation of sensors for routine analysis and monitoring.

Developing metallic nanocatalysts with high reaction activity, selectivity and practical durability is a promising and active subfield in electrocatalysis. In the classical “bottom‐up” approach to synthesize stable nanomaterials by chemical reduction, stabilizing additives such as polymers or organic surfactants must be present to cap the nanoparticle to prevent material bulk aggregation. In recent years, biological systems have emerged as green alternatives to support the uncoated inorganic components. One key advantage of biological templates is their inherent ability to produce nanostructures with controllable composition, facet, size and morphology under ecologically friendly synthetic conditions, which are difficult to achieve with traditional inorganic synthesis. In addition, through genetic engineering or bioconjugation, bio‐templates can provide numerous possibilities for surface functionalization to incorporate specific binding sites for the target metals. Therefore, in bio‐templated systems, the electrocatalytic performance of the formed nanocatalyst can be tuned by precisely controlling the material surface chemistry. With controlled improvements in size, morphology, facet exposure, surface area and electron conductivity, bio‐inspired nanomaterials often exhibit enhanced catalytic activity towards electrode reactions. In this Review, recent research developments are presented in bio‐approaches for metallic nanomaterial synthesis and their applications in electrocatalysis for sustainable energy storage and conversion systems.