Doped Diamond Films with Nanostructured Surfaces for Ammonia Synthesis via Electrochemical Nitrogen Fixation under Ambient Conditions

Project: Research

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Synthesis of ammonia through electrochemical reduction of nitrogen by using electrocatalysts under ambient conditions has been proposed as a dramatic alternative to the conventional Haber–Bosch process that requires high temperature and pressure. However, the ammonia yield rate and Faradic efficiency of the current electrochemical nitrogen reduction processes are unsatisfactorily enslaved by the weak nitrogen adsorption on the active sites of an electrocatalyst and the difficulty in N≡N cleavage there. Thus, developing an electrocatalyst with high-efficiency active sites for promoting nitrogen reduction reaction (NRR) has important scientific and application values. Basically, an ideal NRR electrocatalyst should possess the features such as high intrinsic catalytic reactivity and selectivity toward NRR, large active surface, and outstanding mechanical and chemical stabilities. Due to the fact that transition metals have commonly higher activity for hydrogen evolution reaction (HER) which competes with NRR and leads to a poor NRR selectivity, metal-free electrocatalysts have attracted broad interest as a promising candidate for NRR.Diamond has a series of inherent properties favorable for electrocatalytic NRR; and more importantly, it has a large electrochemical potential window, which enables to suppress the competitive HER and thus to achieve a high NRR selectivity. Nevertheless, the research on utilizing diamond as an electrocatalyst for NRR is still in its infancy. In this project, we propose to develop new high-efficiency electrocatalysts for ammonia synthesis based on nanostructured diamond films. The basic idea is to endow diamond with balanced electrical conductivity and NRR efficiency (activity and selectivity) through doping, and as well to increase the active area and improve the NRR performance based on field-induced enhancement effects through surface nanostructuring of diamond films. To accomplish the targets of this project, we will prepare boron-doped and boron/nitrogen co-doped diamond nanostructure arrays by microwave plasma chemical vapor deposition and subsequent in situ reactive ion etching. The effects of the factors such as the doping concentration of heteroatoms, and the geometry, aspect ratio, and distribution density of diamond nanostructure arrays on the NRR performance will be elucidated. Through comprehensive characterization and theoretical simulation, the origin of NRR activity and reaction paths on doped diamond will be revealed, and the catalytic enhancement mechanism associated with the surface nanostructuring will be demonstrated. Implementation of this project will provide further understanding for the design and development of new metal-free carbon-based electrocatalysts for high-efficiency nitrogen fixation and promote the advance of ammonia synthesis technology. 


Project number9042885
Grant typeGRF
Effective start/end date1/10/19 → …