Effects of Surfactants on the Size Distribution and Electrocatalytic Nitrite Reduction of Uniformly Dispersed Au Nanoparticles

The electrocatalytic nitrite reduction reaction (NO2–RR) occurs under mild conditions at ambient temperature and pressure and can convert nitrite pollution into recycled ammonia. This method has great application potential in the purification of the water environment and the field of synthetic ammonia. In this article, we present a method to synthesize relatively uniformly dispersed gold nanoparticles on the surface of carbon cloth fibers (Au@CC) by hydrothermal self-assembly growth and calcination without the use of adhesive in the process. We studied the influence of different surfactants on the distribution and particle size of gold nanoparticles on carbon cloth by mechanism study and explored their effects on NO2–RR performance. The results showed that Au@CC with gold nanoparticles relatively uniformly dispersed on the surface of carbon cloth fibers and small particle size (≈86.2 nm) could be obtained when the sample was synthesized by the surfactant sodium dodecyl sulfate (SDS). This is mainly due to the strong coordination between SDS and the gold precursor and that the hydrophobic group of SDS can interact with the surface carbon cloth. When performed in the 0.1 M phosphate buffered saline (PBS) (with 0.1 M NaNO2) solution, the Au@CC-SDS electrode gave a high NH3 yield of 1249.1 μg h–1 cm–2 and faradaic efficiency of 80.7%. The density functional theory (DFT) calculations clarified the electrocatalytic reaction mechanism of the NO2–RR to NH3 on the Au active site. Thus, this study demonstrated that SDS is beneficial to the formation of relatively uniformly dispersed gold nanoparticles supported on carbon fiber cloth (Au@CC) and proved that gold-based nanomaterials are a promising catalyst for electrocatalytic NO2–RR ammonia synthesis.

电催化亚硝酸根还原反应（electrocatalytic nitrite reduction reaction, NO2–RR）可在常温常压的温和条件下进行，能够将亚硝酸根污染物转化为可回收利用的氨。该方法在水环境净化及合成氨领域具备优异的应用潜力。本文报道了一种无需使用粘结剂，通过水热自组装生长结合煅烧工艺，在碳纤维布纤维表面合成分散性相对均匀的金纳米颗粒（Au@CC）的方法。我们通过机理研究考察了不同表面活性剂对碳纤维布表面金纳米颗粒分布与粒径的影响，并探究了其对NO2–RR催化性能的调控作用。研究结果表明，当以十二烷基硫酸钠（sodium dodecyl sulfate, SDS）作为表面活性剂合成样品时，可获得金纳米颗粒分散均匀、粒径约为86.2 nm的Au@CC复合材料。这一现象主要源于SDS与金前驱体之间的强配位作用，同时SDS的疏水基团可与碳纤维布表面发生相互作用。在含有0.1 M NaNO2的0.1 M磷酸盐缓冲溶液（phosphate buffered saline, PBS）中进行测试时，Au@CC-SDS电极展现出1249.1 μg h–1 cm–2的高氨产率以及80.7%的法拉第效率。密度泛函理论（density functional theory, DFT）计算阐明了Au活性位点上NO2–RR转化为氨的电催化反应机理。综上，本研究证实SDS有助于实现金纳米颗粒在碳纤维布表面的均匀分散，并证明金基纳米材料是一类极具应用前景的电催化NO2–RR合成氨催化剂。