Electro-catalytic conversion of nitrate (NO) to ammonia (NH) via the Nitrate Reduction to Ammonia (NORA) process represents a promising strategy for both ammonia synthesis and environmental remediation. Despite its potential, the efficiency of low-concentration NORA is often hindered by mass transfer limitations, competing byproducts (N and NO), and side reactions such as hydrogen evolution. This study introduces a novel pulsed electro-synthesis technique that alternates the potential to periodically accumulate and transform NO intermediates near a Cu2O@Pd electrode, enhancing the NORA process. Compared with that under potentiostatic conditions, the CuO@Pd electrodes exhibited a higher NORA activity under the optimized pulsed condition, where a NH-N Faradaic efficiency (FE) of 81.2%, a yield rate of 1.08 mg h cm and a selectivity efficiency (SE) of 81.5%, were achieved. In-situ characterization revealed an enhancement mechanism characterized by optimized adsorption of the key *NO intermediate, followed by the hydrogenation path “*N → *NH → *NH→ *NH”. Further investigations indicated the electro-catalytic synergies between Pd sites and Cu species, where the Pd atoms were the reaction sites for the H adsorption while the Cu species were responsible for the NO activation. This research offers a novel insight into a method of enhancing low-concentration NORA.

中文翻译：

---

脉冲电催化可通过 Cu2O@Pd 串联催化剂将低浓度硝酸盐有效转化为氨


通过硝酸盐还原为氨 (NORA) 过程将硝酸盐 (NO) 电催化转化为氨 (NH) 代表了氨合成和环境修复的一种有前景的策略。尽管具有潜力，低浓度 NORA 的效率常常受到传质限制、竞争性副产物（N 和 NO）以及析氢等副反应的阻碍。这项研究引入了一种新颖的脉冲电合成技术，该技术可以交替电势以在 Cu2O@Pd 电极附近周期性地积累和转化 NO 中间体，从而增强 NORA 过程。与恒电位条件下相比，CuO@Pd电极在优化的脉冲条件下表现出更高的NORA活性，NH-N法拉第效率（FE）为81.2%，产率为1.08 mg h cm，选择性效率（ SE）达到了81.5%。原位表征揭示了一种增强机制，其特征在于关键*NO中间体的优化吸附，随后是氢化路径“*N→*NH→*NH→*NH”。进一步的研究表明 Pd 位点和 Cu 物种之间存在电催化协同作用，其中 Pd 原子是 H 吸附的反应位点，而 Cu 物种负责 NO 活化。这项研究为增强低浓度 NORA 的方法提供了新颖的见解。