Advancing nitrate reduction to ammonia: insights into mechanism, activity control, and catalyst design over Pt nanoparticle-based ZrO2.

The reduction of nitrogen oxides (NOx) to NH3, or N2 represents a crucial step in mitigating atmospheric NO3 and NO2 emissions, a significant contributor to air pollution. Among these reduction products, ammonia (NH3) holds particular significance due to its utility in nitrogen-based fertilizers and its versatile applications in various industrial processes. Platinum-based catalysts have exhibited promise in enhancing the rate and selectivity of these reduction reactions. In this study, we employ density functional theory (DFT) calculations to explore the catalytic potential of Pt nanoparticle (PtNP)-supported ZrO2 for the conversion of NO3 to NH3. The most favorable pathway for the NO3 reduction to NH3 follows a sequence, that is, NO3 → NO2 → NO → ONH → ONH2/HNOH → NH2/NH → NH2 → NH3, culminating in the production of valuable ammonia. The introduction of low-state Fe and Co dopants into the ZrO2 support reduces energy barriers for the most challenging rate-determining hydrogenation step in NOx reduction to NH3, demonstrating significant improvements in catalytic activity. The incorporation of dopants into the ZrO2 support results in a depletion of electron density within the Pt cocatalyst resulting in enhanced hydrogen transfer efficiency during the hydrogenation process. This study aims to provide insights into the catalytic activity of platinum-based ZrO2 catalysts and will help design new high-performance catalysts for the reduction of atmospheric pollutants and for energy applications.

On the Evolution of Additive Manufacturing (3D/4D Printing) Technologies: Materials, Applications, and Challenges.

The scientific community is and has constantly been working to innovate and improve the available technologies in our use. In that effort, three-dimensional (3D) printing was developed that can construct 3D objects from a digital file. Three-dimensional printing, also known as additive manufacturing (AM), has seen tremendous growth over the last three decades, and in the last five years, its application has widened significantly. Three-dimensional printing technology has the potential to fill the gaps left by the limitations of the current manufacturing technologies, and it has further become exciting with the addition of a time dimension giving rise to the concept of four-dimensional (4D) printing, which essentially means that the structures created by 4D printing undergo a transformation over time under the influence of internal or external stimuli. The created objects are able to adapt to changing environmental variables such as moisture, temperature, light, pH value, etc. Since their introduction, 3D and 4D printing technologies have extensively been used in the healthcare, aerospace, construction, and fashion industries. Although 3D printing has a highly promising future, there are still a number of challenges that must be solved before the technology can advance. In this paper, we reviewed the recent advances in 3D and 4D printing technologies, the available and potential materials for use, and their current and potential future applications. The current and potential role of 3D printing in the imperative fight against COVID-19 is also discussed. Moreover, the major challenges and developments in overcoming those challenges are addressed. This document provides a cutting-edge review of the materials, applications, and challenges in 3D and 4D printing technologies.