【Frontiers in HaiChuan Chemical Technology】Scientists from the University of Electronic Science and Technology have successfully recovered high-purity ammonia from wastewater, contributing to the development of a closed-loop utilization system for nitrogen resources
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Scientists have successfully recovered high-purity ammonia from wastewater, helping to establish a closed-loop utilization pathway for nitrogen resources. Recently, Jin Zhaoyu, a specially appointed researcher at the University of Electronic Science and Technology, and his team developed and implemented a new type of photothermal-electrocatalytic synergistic interface system. At the core of this system is a \"Janus-structured\" bifunctional electrode: one side is responsible for electrocatalytically reducing nitrogen-containing substances in wastewater or air, such as nitrates, to ammonia, while the other side heats the interface through photothermal effects, enabling the rapidly evaporated ammonia to be separated. Through this synergistic mechanism of \"reacting while separating,\" the team successfully overcame the key challenges of low product concentration and poor separation efficiency in the electrochemical synthesis of ammonia. In the experiments, this system was used to treat wastewater and even nitrogen sources in the air, thereby extracting high-concentration pure ammonia; the purity and concentration of this ammonia were sufficient to enable ammonia fuel cells to generate electricity stably. In addition to the breakthroughs in devices, the team also discovered several important new phenomena and mechanisms. For example, it demonstrates that adjusting the photothermal and wettability properties of the interface can significantly improve the evaporation efficiency of ammonia ； Furthermore, the in-situ scanning electrochemical microscopy technique was used to directly observe how the photothermal field accelerates the ammonia release process. These findings not only provide new methods for improving the efficiency of electrocatalytic reactions, but also offer new approaches for the simultaneous synthesis and purification of other low-boiling-point products in the future. In short, the team’s work not only proposes a greener and more efficient way of utilizing environmental nitrogen resources, but also opens up new research avenues in the field of \"multi-field coupled electrocatalysis\". Jin Zhaoyu believes that the most promising application area for this achievement is the recovery and utilization of nitrogen resources from industrial or agricultural wastewater. By integrating the photothermal-electrocatalytic synergistic interface system proposed by this team into the wastewater treatment process, it is possible to achieve on-site conversion of nitrogen-containing pollutants such as nitrates and the recovery of high-purity ammonia products. This \"treat while producing\" approach not only helps to reduce the burden of water pollution but also transforms nitrogen, which is otherwise considered a pollutant, into valuable energy sources or fertilizer ingredients, thereby shifting traditional wastewater treatment from a focus on removal to one centered on resource utilization. Against the backdrop of carbon neutrality and resource recycling, this technology is expected to become a key component in the future nitrogen cycle management system.
It is understood that there is an increasing global demand for clean energy and resource recycling, and ammonia (NH3) serves as a key link connecting the three objectives of energy, resources, and the environment. On the one hand, ammonia is an essential fertilizer ingredient in global agricultural production ； On the other hand, ammonia is also widely regarded as a promising zero-carbon fuel carrier, suitable for hydrogen storage and transportation as well as direct combustion for power generation. But the reality is that the traditional method of ammonia synthesis (the Haber-Bosch process) remains highly dependent on fossil fuels, operates under high temperature and pressure conditions, and accounts for approximately 1–2% of global carbon emissions each year. This centralized, large-scale, and energy-intensive production system not only results in a huge carbon footprint but also struggles to meet the growing demand for ammonia on a distributed, small-scale basis, a problem that is particularly evident in underdeveloped regions. Meanwhile, large amounts of nitrogen-containing waste exist in the human environment in various forms, such as agricultural effluents and industrial wastewater, as well as urban emissions, which are typically rich in active nitrogen compounds like nitrates and ammonia. If not properly managed, these substances not only cause eutrophication of water bodies, soil acidification, and air pollution, but also lead to the loss of valuable nitrogen resources. In fact, the amount of nitrogen fixed artificially globally today has exceeded the total amount fixed naturally, resulting in a severe imbalance in the nitrogen cycle. Therefore, the team wondered whether it might be possible to \"recover\" the lost nitrogen resources from the environment and convert them back into valuable ammonia products that can be utilized Focusing on this issue, the team has long been committed to the field of \"sustainable energy and environmental development,\" attempting to reduce nitrogen in its oxidized form in the environment to ammonia through electrochemical reduction. Theoretically, this process offers advantages in terms of being green, efficient, and operating in-situ; however, in practice it faces two key bottlenecks: first, the ammonia concentration produced by existing electrocatalytic systems under normal conditions is too low to meet practical application requirements ； Secondly, the ammonia product is difficult to separate and concentrate efficiently, which further increases the overall energy consumption and costs of the system. Therefore, this study addresses the long-standing technical challenges related to low ammonia production efficiency, difficulty in separation, and poor effectiveness in electrocatalytic ammonia synthesis. By introducing the concept of \"photothermal coupling,\" the team aims to develop a new type of functional interface that can enhance both the efficiency of electrocatalytic reactions and the ability to extract the resulting products, thereby enabling the in-situ enrichment and direct purification of ammonia produced at low concentrations. Its goal is not only to increase the rate of ammonia production and recovery efficiency, but also to explore a closed-loop utilization pathway for nitrogen resources from the environment to fuel, thereby providing new technical solutions for sustainable development.
Throughout the entire research process, what impressed Jin Zhaoyu the most was the complete process from conceptualization of the principles to experimental verification. He and his team initially came up with an idea: could the introduction of a photothermal field be used to assist the electrocatalytic reaction process, thereby increasing the rate of ammonia production and facilitating its rapid release at the interface? Although this approach is theoretically feasible, in practice they face numerous engineering and mechanical uncertainties. Throughout the progress of this project, Jin Zhaoyu discussed repeatedly with the students, analyzing each experimental design and observed phenomenon in detail by breaking them down step by step based on the coupling mechanism of \"interface reaction–transport–separation\". For example, they were puzzled for a long time by the difficulty in increasing ammonia concentrations; eventually, by adjusting the thermal conductivity structure of the photothermal layer as well as the interfacial wettability, they achieved rapid release and accumulation of ammonia molecules, resulting in a significant improvement in performance. More importantly, during the research they also received careful guidance from Professor Yu Guihua of The University of Texas at Austin in Germany. “The long-term research experience of Professor Yu’s team in solar water evaporation and interface purification has provided valuable insights into how the control of the interfacial heat field affects the gas-liquid separation process. Through discussions with Teacher Yu, we further optimized the interface structure design, making breakthroughs in key parameters such as heat transfer pathways and interface tension control, and successfully resolved the issue of ammonia lingering easily during the reaction process and being difficult to separate. ”Jin Zhaoyu said. During the review process of the relevant paper, the team received positive feedback from many peers. One of the reviewers commented, \"The photothermal-electrocatalytic synergistic interface proposed by the authors is an innovative solution to the challenge of separating ammonia at low concentrations; it successfully enables the continuous extraction of high-purity ammonia from air and wastewater, and can be directly applied in ammonia fuel cells, holding significant scientific importance and practical prospects.\" ”Another reviewer noted: “By employing material-driven and multi-physics field coupling strategies, this work develops a novel and practical electrocatalytic system. It not only features an advanced concept but also boasts a comprehensive and logically sound system design, making it of great significance as a reference for research in sustainable energy and the nitrogen cycle.” ”These two evaluations highly recognize the team’s efforts in method innovation and system integration, and also reflect the reviewers’ strong approval of the application prospects of this achievement in the fields of green energy and resource recycling. Currently, the team has developed subsequent systematic plans for this research, with the primary goal of further deepening the understanding of the fundamental mechanisms at the light-heat-electric multi-field coupling interface. Next, it will focus on developing an in-situ characterization platform under multi-field collaborative conditions, combining with the in-situ electrochemical titration analysis techniques that have been developed over time by the research team, in order to achieve dynamic visualization and quantitative analysis of the formation, migration, and transformation processes of intermediates at the reaction interface. Through this platform, it aims to accelerate the screening and discovery of high-performance, multi-functional integrated interface materials, and to establish a closed-loop system ranging from mechanism understanding to material development. At the same time, the team is also exploring the extension of this strategy to other systems of low-boiling-point electrosynthetic products, and plans to conduct preliminary demonstrations using small integrated devices in order to advance this concept toward more practical applications in energy and resource recovery.
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