Data underlying the publication: Investigating the influence of a thin copper film coated on nickel plates through physical vapor deposition for electrocatalytic nitrate reduction

The removal of nitrate (NO3 − ) from water and its subsequent valorization for various applications are crucial due to environmental, health, and economic considerations. A promising method for its removal is the process of electrocatalytic reduction of nitrate. Copper/nickel (Cu/Ni) composite electrodes have demonstrated potential for this process in aqueous solution, however, the effect of thin Cu film coated on Ni using physical vapor deposition (PVD) has not been investigated for NO3 − removal. Here, the PVD technique was employed to deposit a thin film of Cu onto a Ni plate to form Cu-Ni composite electrodes of varying Cu thicknesses (25–100 nm), enabling the investigation of the influence of the Cu film thickness on NO3 − reduction. Electrodes prepared using PVD were utilized for electrocatalytic nitrate reduction (NO3RR) for the first time. The Cu-Ni electrodes were analyzed using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to examine the deposited Cu film which is critical for NO3 − reduction and ammonium (NH4 + ) selectivity. The Cu film was found to be uniformly distributed on the Ni plate without any additional contamination. Cyclic voltammetry was performed to obtain the information on electron transfer between the Cu-Ni electrode and the nitrogen (N2 ) species on the surface. NO3 − was primarily reduced to NH4 + , with no significant difference in the NO3 − conversion rate observed as a function of the Cu thickness. As the Cu thickness increased, the current density decreased. This study also investigated the effect of stirring on NO3 − reduction, considering potential applications where rotation or stirring is not feasible such as in some batteries. The findings of this investigation indicate that thin film coated electrodes fabricated using the PVD method exhibit capability for NO3 − elimination through electrocatalytic reduction processes.<br>

出于环境、健康与经济层面的多重考量，从水体中脱除硝酸盐（NO3−）并将其资源化应用于诸多场景具有重要意义。针对硝酸盐脱除，颇具应用前景的方法为电催化还原工艺。铜/镍（Cu/Ni）复合电极已在水溶液中展现出用于该工艺的潜力，但针对通过物理气相沉积（PVD）法在镍基底上沉积的薄铜膜在硝酸盐脱除中的作用，目前尚未开展相关研究。
本研究采用物理气相沉积（PVD）技术，在镍板上沉积厚度为25~100 nm的铜薄膜，制备得到不同铜膜厚度的Cu-Ni复合电极，以此探究铜膜厚度对硝酸盐电催化还原（NO3RR）过程的影响。本研究首次将PVD法制备的电极用于电催化硝酸盐还原反应。
通过X射线光电子能谱（XPS）与扫描电子显微镜（SEM）对所制备的Cu-Ni电极进行表征，以分析与硝酸盐还原及铵根（NH4+）选择性密切相关的沉积铜膜特性。结果表明，铜膜均匀分布于镍板表面，未引入额外污染。采用循环伏安法测试以获取Cu-Ni电极与表面氮（N2）物种间电子转移的相关信息。实验发现，硝酸盐主要被还原为铵根，且硝酸盐转化率随铜膜厚度变化未出现显著差异；但随着铜膜厚度增加，电流密度有所降低。
考虑到部分场景（如部分电池体系）无法实现旋转或搅拌，本研究同时探究了搅拌对硝酸盐电催化还原过程的影响。本研究结果表明，采用PVD法制备的薄膜包覆电极，可通过电催化还原工艺实现硝酸盐的高效脱除。