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@INPROCEEDINGS{LunaBarron:1020298,
      author       = {Luna Barron, Ana Laura and Azua Humara, Ana Daniela and
                      Eichel, Rüdiger-A. and Mechler, Anna},
      title        = {{I}nsights into {E}fficient {E}lectrochemical {N}itrate
                      {R}eduction to {A}mmonia: {R}eaction {E}nvironment and
                      {M}etal {E}lectrode},
      reportid     = {FZJ-2024-00043},
      year         = {2023},
      abstract     = {The ammonia economy is mainly driven by the inorganic
                      fertilizer demand. Around $70\%$ of worldwide ammonia
                      production is used as feedstock for fertilizers. The global
                      ammonia production is about 176 Mt per year, and it is
                      expected to increase by $40\%$ by 2050. 1,2 However, the
                      actual ammonia economy seriously pollutes the air, soil, and
                      water, contradicting climate neutrality goals. Pollution
                      comes from different parts of the ammonia value chain, from
                      its production to its transformation as fertilizers. While
                      fertilizers are essential in providing sufficient food to
                      feed our planet, they have been the main cause of water
                      pollution. Fertilizers are the source of nitrogen nutrients
                      (nitrates, NO3- ), which allow crops to grow. However, less
                      than $50\%$ of the applied nitrates nurture crops, while the
                      rest inevitably leaches to the groundwater, polluting water.
                      A high level of nitrates makes water unsuitable to drink and
                      harms the natural environment, particularly via
                      eutrophication.3 Therefore, it is of vital importance to
                      develop sustainable technologies that allow treating water
                      from nitrates. Electrocatalysis is a promising technology
                      for such a challenge. Electrocatalysis could not only
                      eliminate nitrates from water, but also conveniently convert
                      them back into ammonia, generating an added value apart from
                      nitrogen remediation. Although electrocatalytic nitrogen
                      reduction to ammonia is promising, its practical application
                      is hindered by the lack of an electrocatalyst that
                      simultaneously can show high stability, activity, and
                      selectivity. For instance, some transition metal-based
                      electrocatalysts (e.g., Rh, Pt, Cu, Ir) have shown
                      appreciable activity, but not simultaneously selectivity
                      towards ammonia in acidic or alkaline media.4,5 Clearly, the
                      development of a “champion electrocatalyst” for such a
                      reaction is not trivial. Our primary research focus is to
                      tailor electrocatalyst properties for nitrates to ammonia
                      rationally by identifying active sites favorable for
                      efficient ammonia evolution and understanding the effect of
                      the reaction environment (nitrate concentration, pH, applied
                      voltage, and presence of other ions) on activity and
                      selectivity.As the initial phase of our research, the
                      electrochemical investigation was carried out using metal
                      foil electrodes (Ti, Ag, Au, Cu, Bi, Pd, Zn, Ta, and Mo). We
                      observed that in a reaction environment rich in protons
                      (i.e., pH 1), selectivity towards ammonia increases with
                      nitrate concentration. In such an acidic media, the highest
                      faradaic efficiencies (FE) to NH3 were reached at an applied
                      potential of -1V versus RHE for most of the tested metal
                      foils. For example, Ti reached a faradaic efficiency of
                      $34\%$ with a current partial density to ammonia of -36 mA
                      cm-2 using 0.4M [NO3-] at pH 1. Because an acid media of pH
                      1 with a high concentration of nitrated (0.4 M) favored the
                      formation of ammonia, the intrinsic activity of the metals
                      was investigated at such conditions at -1V vs. RHE, Figure
                      shown. Ti, Au, and Cu showed the highest efficiency with
                      notable corrosion resistance. The effect of higher pH was
                      also investigated, showing Cu, Au, Ti, and Ag can also
                      catalyze ammonia formation in specific pH conditions.},
      month         = {Dec},
      date          = {2023-12-04},
      organization  = {GeCatS Infoday "Electrification of
                       catalytic processes", Frankfurt
                       (Germany), 4 Dec 2023 - 4 Dec 2023},
      subtyp        = {Outreach},
      cin          = {IEK-9},
      cid          = {I:(DE-Juel1)IEK-9-20110218},
      pnm          = {1232 - Power-based Fuels and Chemicals (POF4-123) / iNEW2.0
                      (BMBF-03SF0627A)},
      pid          = {G:(DE-HGF)POF4-1232 / G:(DE-Juel1)BMBF-03SF0627A},
      typ          = {PUB:(DE-HGF)24},
      doi          = {10.34734/FZJ-2024-00043},
      url          = {https://juser.fz-juelich.de/record/1020298},
}