Nitrate electroreduction to ammonia has broad prospects as a complementary route to the energy-intensive Haber–Bosch process. Currently, most electrocatalytic NO₃⁻-to-NH₃ transformations are achieved in alkaline electrolytes, which not only require a large power supply but also pose additional challenges for accurate quantification and large-scale separation of NH₃. Herein, the silicon nanowire (black silicon) uniformly modified with Cu nanoparticles (Cu–Si NWs) is designed for the photoelectrochemical nitrate reduction reaction (PEC NO₃RR) in strong acidic electrolyte. Under AM 1.5G illumination, the Cu–Si NWs achieve a remarkably positive onset potential of 0.3 V vs. the RHE and an impressive saturated photocurrent density of −34.29 mA cm⁻² in 0.5 M H₂SO₄. More importantly, the faradaic efficiency of ammonium (NH₄⁺) and corresponding solar-to-NH₄⁺ efficiency reach up to 97.03% and 51.07%, respectively. Mechanistic investigations uncover the appropriate Schottky contact in Cu/Si interfaces, which facilitates charge transfer effectively, contributing to the low onset potential and high photocurrent density. In situ experiments and theoretical analysis have further confirmed that the incorporation of Cu effectively accelerates the activation and protonation steps of NO₃⁻. Moreover, this PEC system exhibits excellent stability and great potential for environmental remediation in simulated industrial wastewater treatment experiments. This work introduces a strategy for fabricating highly efficient PEC devices for removing nitrate contaminants in strong acidic media.

中文翻译：

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铜装饰黑硅上光电化学硝酸盐反硝化反应向酸性氨合成


硝酸盐电还原制氨作为能源密集型 Haber-Bosch 工艺的补充路线具有广阔的前景。目前，大多数电催化 NO₃ ^到 NH₃ 的转化是在碱性电解质中实现的，这不仅需要大电源，而且对 NH₃ 的准确定量和大规模分离提出了额外的挑战。在此，用 Cu 纳米颗粒 （Cu-Si NWs） 均匀改性的硅纳米线 （black silicon） 设计用于在强酸性电解质中进行光电化学硝酸盐还原反应 （PEC NO₃RR）。在 AM 1.5G 照明下，Cu-Si NW 实现了 0.3 V 的显著正起始电位。RHE 和 0.5 M H₂SO₄ 中令人印象深刻的 −34.29 mA ^cm-2 饱和光电流密度。更重要的是，铵 （NH₄⁺） 的法拉第效率和相应的太阳能到 NH₄⁺ 的效率分别达到 97.03% 和 51.07%。机理研究揭示了 Cu/Si 界面中合适的肖特基接触，这有效地促进了电荷转移，有助于实现低起始电位和高光电流密度。原位实验和理论分析进一步证实，Cu 的掺入有效地加速了 NO₃⁻ 的活化和质子化步骤。 此外，该 PEC 系统在模拟工业废水处理实验中表现出优异的稳定性和巨大的环境修复潜力。这项工作介绍了一种制造高效 PEC 装置的策略，用于去除强酸性介质中的硝酸盐污染物。