Ammonia (NH3) is an important feedstock for industry, an ideal energy carrier, and a perspective storage media for hydrogen. Recently, electrochemical NO3− reduction under acidic conditions has received considerable attention but it suffers from limited efficiency especially under low NO3− concentration. Here, we report an in-situ formed positively charged polyethyleneimine-modified Cu under acidic conditions as a catalyst-electrolyte interface (CEI) for electrochemical NO3− reduction to NH3. Such CEI can effectively accumulate NO3− anions via static interactions and accelerate *NO hydrogenation to *NOH by weakening *NO intermediate adsorption on Cu site, thereby facilitating NO3−-to-NH3 conversion. Such CEI delivers an increased NH3 Faradaic efficiency (FE) of 83.5% and an impressive half-cell energy efficiency (EE) of 37.1% in 10 mM NO3− solution (pH = 1). The NH3 FE and EE can further increase to 90.2% and 44.1% in 0.5 M NO3−, respectively. The high EE of CEI surpasses previously reported catalyst performances for NO3− reduction. Finally, we demonstrate the feasibility of a novel NO3−-furfural battery, showcasing a self-power electrocatalytic system capable of simultaneously treating NO3− pollutants, generating value-added NH3 and upgrading biomass. This work offers valuable insights into the construction of a catalyst-electrolyte interface to enhance the efficiency of NH3 synthesis.

中文翻译：

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具有超高能效的酸性硝酸盐电还原

氨 （NH3） 是工业的重要原料、理想的能源载体和氢的前瞻性储存介质。最近，酸性条件下的电化学 NO3− 还原受到了相当大的关注，但其效率有限，尤其是在低 NO3− 浓度下。在这里，我们报道了在酸性条件下原位形成的带正电荷的聚乙烯亚胺改性 Cu 作为电化学 NO3− 还原为 NH3 的催化剂-电解质界面 （CEI）。这种 CEI 可以通过静态相互作用有效地积累 NO3− 阴离子，并通过削弱 Cu 位点的 *NO 中间吸附来加速 *NO 氢化为 *NOH，从而促进 NO3− 到 NH3 的转化。这种 CEI 在 10 mM NO3− 溶液 （pH = 1） 中提供了 83.5% 的 NH3 法拉第效率 （FE） 和 37.1% 的令人印象深刻的半电池能效 （EE）。NH3 FE 和 EE 在 0.5 M NO3− 中可分别进一步增加到 90.2% 和 44.1%。CEI 的高 EE 超过了以前报道的催化剂在 NO3− 还原方面的性能。最后，我们展示了新型 NO3−-糠醛电池的可行性，展示了一种能够同时处理 NO3− 污染物、产生增值 NH3 和升级生物质的自供电电催化系统。这项工作为构建催化剂-电解质界面以提高 NH3 合成效率提供了有价值的见解。