研究背景
Scheme 1. Schematic diagram of industrial production and proposed artificial photosynthesis of ammonia.
本文要点
1. 通过金属辅助化学刻蚀法和光沉积法合成了铜负载的硅纳米线阵列(Cu-Si NWs), 从而实现了酸性介质中高效光电催化硝酸盐还原。
2. 揭示了Cu/Si肖特基界面可有效促进电荷转移，抑制载流子复合，增强电子-空穴对分离和扩散，从而实现低起始电位和高光电流密度。
3. 原位ATR-FTIR和DFT分析表明，Cu位点可优化中间体吸附并促进水解离，从而为含氮中间体的高效氢化提供大量*H物种。
图文内容
Fig. 1. Morphology and structure characterization. Side-view SEM image of (a) Si NWs and (b, c) Cu-Si NWs. (d, e) HRTEM image and (f) the corresponding HADDF and EDS images of Cu-Si NWs. (Scale bars: a. 1 µm, b. 1 µm, c. 200 nm d. 5 nm, e. 1 nm, f. 200 nm) (g) XRD pattern and XPS spectra (h) Cu 2p, (i) Cu LMM of Cu-Si NWs.
Fig. 2.PEC NO3RR performance. (a) LSV plots of p-Si, Si NWs, and Cu-Si NWs for PEC NO3RR in 0.5 M H2SO4 with and without (w/o) 100 mM NO3− (scan rate: 20 mV s−1). (b) Transient photocurrent responses of p-Si, Si NWs, and Cu-Si NWs at −0.4 V in 0.5 M H2SO4 with 100 mM NO3−. (c) 1H NMR spectra of the electrolytes collected after PEC NO3RR electrolysis using K14NO3 and K15NO3 feedstocks and the referenced spectrum of 14NH4Cl and 15NH4Cl. (d) Faradaic efficiency and (e) yield rate of NH4+ for Si NWs and Cu-Si NWs at various potentials. (f) Comparison of NH4+ yield rates at −0.4 V vs. RHE using indophenol blue method and 1H NMR. (g) IPCE spectrum and solar-to-NH4+ efficiency of Si NWs and Cu-Si NWs. (h) Stability test of large-scale Cu-Si NWs photocathode (4 cm2) for PEC NO3RR at −0.4 V vs. RHE in 0.5 M H2SO4 with 100 mM NO3−.
Fig. 3. The mechanism of Cu-Si NWs for PEC NO3RR. (a) UV-Vis diffuse reflection spectrum and (b) EIS plots of p-Si, Si NWs, and Cu-Si NWs. (c) Calculated ABPE curves, (d) charge injection efficiency, and (e) time-resolved photoluminescence (TR-PL) spectra of p-Si, Si NWs and Cu-Si NWs. (f) Mott-Schottky curves and (g) UPS plots of Si NWs and Cu-Si NWs. (h) The electron transfer mechanism of the Cu-Si NWs in 0.5 M H2SO4 with 100 mM NO3− under AM 1.5 G solar irradiation.
Fig. 4. Operando infrared spectrocopic studies and DFT calculations. In-situ ATR-FTIR spectra of (a) Cu-Si NWs and (b) Si NWs in 0.5 M H2SO4 with 100 mM NO3−. (c) Differential charge density of Cu/Si NWs interface. ISO surface values of the blue and red are +0.04 and –0.04 e–1, respectively. (d) The Gibbs free energy for nitrate reduction to ammonia on Si NWs and Cu-Si NWs. The inset reprents the corresponding adsorption configurations of intermediates on the electrodes. (e) The Gibbs free energy for hydrogen evolution reaction on Si NWs and Cu-Si NWs.
Fig. 5. PEC NO3RR performance of Cu-Si NWs in real wastewater treatment. (a) PEC NO3RR stability tests in simulated wastewater containing various interfering species. The inset: the anti-interference studies performed in the presence or absence of electrolytes chemical oxygen demand (COD), Cl–, PO43–, CO32–, Ca2+, Mg2+, Fe3+, Mn2+, and Zn2+ (see Supplementary Materials for detailed concentrations). (b) Global warming potential (GWP) of ammonia production from wastewater by conventional Haber-Bosch process, electrocatalysis, thermal-assisted electrocatalysis, and photoelectrocatalysis.
总结与展望
本文利用Cu-Si NWs光阴极成功实现了硝酸盐污染物高效还原为高附加值的铵盐。这种光电阴极表现出优异的酸性PEC NO3RR性能，具备高达−34.29 mA cm−2的光电流密度，97.03%的法拉第效率和65.91 µmol h−1 cm−2的氨产量。在大面积制备Cu-Si NWs光阴极合成氨过程中展示了其具有持续36小时良好稳定性。本工作证明在Si NWs上引入Cu可以降低界面电荷转移电阻，并提升电荷分离效率，从而显著增强起始电位、光电流密度以及对NO3−选择性生成NH3的能力。通过原位ATR-FTIR和DFT相结合，验证了Cu位点可优化中间体吸附并促进水解离反应，从而为含氮中间体高效加氢提供丰富的*H物种。此外，在模拟废水处理方面，成功地证明了Cu-Si NWs光阴极有效地将NO3−转化为NH3，显示出实际应用前景。本研究揭示了酸性PEC NO3RR在碳中性合成NH3领域具备显著的应用潜力。
文献信息
Yuchan Li, Qi Zhang, Huan Dai, Dong He, Zunjian Ke, Xiangheng Xiao, Photoelectrochemical nitrate denitrification towards acidic ammonia synthesis on copper-decorated black silicon, Energy Environ. Sci. 2024.
DOI: 10.1039/d4ee04438j
https://doi.org/10.1039/d4ee04438j
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