Electrocatalytic nitrate reduction reaction (NitRR) is an efficient route for simultaneous wastewater treatment and ammonia production, but the conversion of NO₃^- to NH₃ involves multiple electron and proton transfer processes and diverse by-products. Therefore, developing ammonia catalysts with superior catalytic activity and selectivity is an urgent task. The distinctive electronic structure of Cu enhances the adsorption of nitrogen-containing intermediates, but the insufficient activation capability of Cu for interfacial water restricts the generation of reactive hydrogen and inhibits the hydrogenation process. In this work, a Ce-doped CuO catalyst (Ce₁₀/CuO) was synthesized by in situ oxidative etching and annealing. The redox of Ce³⁺/Ce⁴⁺ enables the optimization of the electronic structure of the catalyst, and the presence of Ce³⁺ as a defect indicator introduces more oxygen vacancies. The results demonstrate that Ce₁₀/CuO provides an impressive ammonia yield of 3.88 (± 0.14) mmol cm^-2 h^-1 at 0.4 V vs. RHE with an increase of 1.04 mmol cm^-2 h^-1 compared to that of pure CuO, and the FE reaches 93.2% (± 3.4). In situ characterization confirms the doping of Ce facilitates the activation and dissociation of interfacial water, which promotes the production of active hydrogen and thus enhances the ammonia production efficiency.

The electrochemical nitrate reduction reaction (NO₃RR) to ammonia under ambient conditions is a promising approach for addressing elevated nitrate levels in water bodies, but the progress of this reaction is impeded by the complex series of chemical reactions involving electron and proton transfer and competing hydrogen evolution reaction. Therefore, it becomes imperative to develop an electro-catalyst that exhibits exceptional efficiency and remarkable selectivity for ammonia synthesis while maintaining long-term stability. Herein the magnetic biochar (Fe-C) has been synthesized by a two-step mechanochemical route after a pyrolysis treatment (450, 700, and 1000 °C), which not only significantly decreases the particle size, but also exposes more oxygen-rich functional groups on the surface, promoting the adsorption of nitrate and water and accelerating electron transfer to convert it into ammonia. Results showed that the catalyst (Fe-C-700) has an impressive NH₃ production rate of 3.5 mol·h⁻¹·g_cat⁻¹, high Faradaic efficiency of 88%, and current density of 0.37 A·cm⁻² at 0.8 V vs. reversible hydrogen electrode (RHE). In-situ Fourier transform infrared spectroscopy (FTIR) is used to investigate the reaction intermediate and to monitor the reaction. The oxygen functionalities on the catalyst surface activate nitrate ions to form various intermediates (NO₂, NO, NH₂OH, and NH₂) and reduce the rate determining step energy barrier (*NO₃ → *NO₂). This study presents a novel approach for the use of magnetic biochar as an electro-catalyst in NO₃RR and opens the road for solving environmental and energy challenges.

As photothermal conversion agents, carbon nanomaterials are widely applied in polymers for light-triggered shape memory behaviors on account of their excellent light absorption. However, they are usually derived from non-renewable fossil resources, which go against the demand for sustainable development. Biomass-derived carbon nanomaterials are expected as alternatives if they are designed with good dispersibility as well as splendid photothermal properties. Up to date, very few researches focused on this area. Herein, we report a novel light-triggered shape memory composite by incorporating renewable biomass-derived carbon nanomaterials into acrylate polymers without deep purification and processing. These functionalized carbon nanomaterials not only have stable dispersion in polymers as fillers, but also can endow the polymers with excellent and stable thermal and photothermal responsive properties in biological friendly environment. With the introduction of biomass-derived carbon nanomaterials, the mechanical properties of the composites are also further enhanced with the formation of hydrogen bonding between the carbon nanomaterials and the polymers. Notably, the doping of 1% carbon nanomaterials endows the polymer with sufficient hydrogen bonds that not only exhibit excellent thermal and photothermal responsive properties, but also with enough space for the motion of chains. These properties make such composite a promising and safe candidate for shape memory applications, which provide a new avenue in smart fabrics or intelligent soft robotics.