物理化学学报 >> 2024, Vol. 40 >> Issue (3): 2304044.doi: 10.3866/PKU.WHXB202304044

所属专题： 能源电催化

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磷掺杂碳负载ZnxPyOz常温常压下高效电催化合成氨

王佳, 秦清*(), 王哲, 赵旭浩, 陈云菲, 候利强, 刘尚果, 刘希恩*()   

  1. 青岛科技大学化工学院, 山东 青岛 266042
  • 收稿日期:2023-04-24 修回日期:2023-06-13 录用日期:2023-06-14 发布日期:2023-06-27
  • 通讯作者: Email: liuxien@qust.edu.cn (刘希恩)qinqing@qust.edu.cn (秦清)
  • 基金资助:
    山东省泰山学者人才工程(ts201712045); 山东省泰山学者人才工程(tsqn202211162); 国家自然科学基金(22102079); 山东省自然科学基金(ZR2021YQ10)

P-Doped Carbon-Supported ZnxPyOz for Efficient Ammonia Electrosynthesis under Ambient Conditions

Jia Wang, Qing Qin*(), Zhe Wang, Xuhao Zhao, Yunfei Chen, Liqiang Hou, Shangguo Liu, Xien Liu*()   

  1. College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042, Shandong Province, China
  • Received:2023-04-24 Revised:2023-06-13 Accepted:2023-06-14 Published:2023-06-27
  • Contact: Email: liuxien@qust.edu.cn (Xien Liu)qinqing@qust.edu.cn (Qing Qin)
  • Supported by:
    the Taishan Scholar Program of Shandong Province(ts201712045); the Taishan Scholar Program of Shandong Province(tsqn202211162); the National Natural Science Foundation of China(22102079); the Natural Science Foundation of Shandong Province(ZR2021YQ10)

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摘要：

合成氨(NH3)的发展是现代工业进程和人类生存的基石。受氮气(N2)化学惰性的限制，当前的合成氨工业能源消耗高并且排放大量的二氧化碳。电化学氮气还原反应(NRR)，是有望取代高能耗的Haber-Bosch (HB)合成法的一种绿色可持续的合成氨工艺。然而，因氮气以及析氢竞争副反应(HER)导致电催化氮气还原极低的NH3产率和能量转换效率一直是目前人工固氮领域面临的挑战。在本文中，我们报道了一种具有丰富孔结构的磷掺杂碳(PC)负载Zn3(PO4)2/Zn2P2O7纳米复合材料(h-PC/Zn3(PO4)2/Zn2P2O7)，在酸性和中性介质中将N2高效催化转化为NH3。其独特的分级多孔结构提高了表面粗糙度并加快了氮气在催化剂体相中的扩散，这有利于延长氮气在催化剂表面的停留时间以及提高活性位点的利用效率；而多组分的均匀分布可以调节电子结构并优化反应中间体的吸附行为，进而提高活性位点的本征活性。在0.1 mol∙L−1 HCl电解液中，h-PC/Zn3(PO4)2/Zn2P2O7在−0.2 V vs.可逆氢电极(RHE)电位下NH3的产率可以达到38.7 ± 1.2 μg∙h−1∙mgcat−1，法拉第效率为19.8% ± 0.9%。此外，h-PC/Zn3(PO4)2/Zn2P2O7在0.1 mol∙L−1 Na2SO4溶液中同样展现出优异的电催化氮气还原合成氨性能，NH3产率及法拉第效率分别为17.1 ± 0.8 μg∙h−1∙mgcat−1和15.9% ± 0.6%，明显优于PC/Zn3P2、C/ZnO和大多数报道的非贵金属电催化剂。这种优异的性能主要归因于多孔结构有利于传质及多组分活性位点协同效应。此外，我们采用非原位X射线光电子能谱(XPS)、透射电子显微镜(TEM)和X射线衍射(XRD)等表征手段对NRR测试前后h-PC/Zn3(PO4)2/Zn2P2O7的组成和结构变化进行了剖析。在反应后检测到了新增的N物种信号，证明催化剂表面确实发生了氮气还原反应。本研究提供了一种通过同步构建传质通道并耦合不同的活性位点以协同增强NRR活性和选择性的新思路，这对加快绿色制氨工业化具有重大意义。

关键词: 氮气还原反应, 电催化剂, 孔结构, 多活性中心, 协同效应

Abstract:

The development of efficient synthetic routes for ammonia (NH3) production is the cornerstone of the modern industrial processes and human survival. Owing to the chemical inertness of nitrogen, the current ammonia industry suffers from high energy consumption and high CO2 emission. Electrochemical nitrogen reduction reaction (NRR) provides a promising alternative to the energy-intensive Haber-Bosch (HB) process, enabling green and sustainable NH3 production. However, a low NH3 yield and limited energy conversion efficiency due to the chemical inertness of N2 and competitive hydrogen evolution reaction (HER) are still critical challenges in artificial nitrogen fixation using the electrochemical NRR. Herein, we report a hole-enriched P-doped carbon (PC)-supported Zn3(PO4)2/Zn2P2O7 nanocomposite (h-PC/Zn3(PO4)2/Zn2P2O7) for efficient electrocatalytic conversion of N2 to NH3 in both acidic and neutral media. Remarkably, the unique hierarchical porous structure of the h-PC/Zn3(PO4)2/Zn2P2O7 catalyst improves the surface roughness and facilitates the diffusion of N2 within the catalyst layer, thereby prolonging the residence time of N2 and improving the utilization of active sites. The uniform distribution of multiple components modulates the electronic structure of the active sites and optimizes the adsorption behavior of various reaction intermediates, enhancing the intrinsic activity of the catalyst. Benefiting from the porous structure and multicomponent active sites, including the Zn species and PC, the h-PC/Zn3(PO4)2/Zn2P2O7 achieves an excellent NRR performance with an NH3 yield rate of 38.7 ± 1.2 μg∙h−1∙mgcat−1 and Faradaic efficiency (FE) of 19.8% ± 0.9% at −0.2 V vs. reversible hydrogen electrode (RHE) in 0.1 mol∙L−1 HCl electrolyte. Moreover, it delivers a high NH3 yield rate of 17.1 ± 0.8 μg∙h−1∙mgcat−1 with an FE of 15.9% ± 0.6% at −0.2 V vs. RHE in 0.1 mol∙L−1 Na2SO4 solution, which is superior to those of PC/Zn3P2, C/ZnO, and many other non-noble-metal-based electrocatalysts. Ex situ X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) studies were conducted to monitor the changes in the composition and structure of h-PC/Zn3(PO4)2/Zn2P2O7 after being used in NRR. In particular, a new signal of N appeared in the XPS profile after NRR, confirming the occurrence of NRR. This work provides a new strategy for synchronously constructing mass transfer channels and coupling different active sites to synergistically enhance the NRR activity and selectivity of a catalyst, which is of great significance in progressing the industrialization of green ammonia production.

Key words: Nitrogen reduction reaction, Electrocatalyst, Porous structure, Multiple active center, Synergistic effect