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

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 mu g center dot h-1 center dot mgcat-1 and Faradaic efficiency (FE) of 19.8% +/- 0.9% at -0.2 V vs. reversible hydrogen electrode (RHE) in 0.1 mol center dot L-1 HCl electrolyte. Moreover, it delivers a high NH3 yield rate of 17.1 +/- 0.8 mu g center dot h-1 center dot mgcat-1 with an FE of 15.9% +/- 0.6% at -0.2 V vs. RHE in 0.1 mol center dot L-1 Na2SO4 solution, which is superior to those of PC/Zn3P2, C/ZnO, and many other non-noble-metal-based diffraction (XRD) studies were conducted to monitor the changes in the composition and structure of hPC/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.