Abstract
N-doped graphene samples with different N species contents were prepared by a two-step synthesis method and evaluated as electrocatalysts for the nitrate reduction reaction (NORR) for the first time. In an acidic solution with a saturated calomel electrode as reference, the pyridinic-N dominant sample (NGR2) had an onset of 0.932 V and a half-wave potential of 0.833 V, showing the superior activity towards the NORR compared to the pyrrolic-N dominant N-doped graphene (onset potential: 0.850 V, half-wave potential: 0.732 V) and the pure graphene (onset potential: 0.698 V, half-wave potential: 0.506 V). N doping could significantly boost the NORR performance of N-doped graphene, especially the contribution of pyridinic-N. Density functional theory calculation revealed the pyridinic-N facilitated the desorption of NO, which was kinetically involved in the process of the NORR. The findings of this work would be valuable for the development of metal-free NORR electrocatalysts.
Highlights
N-doped graphene samples with different N species contents were prepared by a two-step synthesis method and evaluated as electrocatalysts for the nitrate reduction reaction (NORR) for the first time
We demonstrated that pyridinic-N played the dominant role in the enhanced NORR activity and density functional theory (DFT) calculations were further conducted to reveal the mechanism
After heating at 180 ◦ C for 12 h and cooling down to room temperature, the as-prepared sample was washed by DI water and dried overnight to obtain the N-doped graphene named as NGR1
Summary
N-doped graphene samples with different N species contents were prepared by a two-step synthesis method and evaluated as electrocatalysts for the nitrate reduction reaction (NORR) for the first time. Reducing the nitrate emission from industry effluents is an effective way to limit nitrate pollution since nitric acid is widely used in several industries, such as the nuclear industry and the explosives industry [6,7]. The wastewater from these industries could be strongly acidic with a high concentration of nitrate, which is hardly treated by traditional biological treatments [7]. The sluggish kinetics of the nitrate reduction reaction (NORR) leads to an extreme demand for robust electrocatalysts [9,10,11]
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