School of Chemical and Biological Engineering, Institute of Chemical Process (ICP), Institute of Engineering Research, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea.
School of Chemical and Biological Engineering, Institute of Chemical Process (ICP), Institute of Engineering Research, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea.
Chemosphere. 2024 Apr;353:141537. doi: 10.1016/j.chemosphere.2024.141537. Epub 2024 Feb 24.
Despite the great potential of electrochemical nitrate reduction as a hydroxylamine production method, this strategy has not been sufficiently examined, and the effects of electrode material type on the selectivity and efficiency of this reduction remain underexplored. To bridge this gap, the present study evaluated six metals (Ag, Cu, Ni, Sn, Ti, and Zn) as cathode materials for the electrochemical reduction of nitrate to hydroxylamine, showing that the selectivity of hydroxylamine production was maximal for Sn, while the corresponding faradaic and energy utilization efficiencies were maximal for Ti. Although all tested materials favored nitrate reduction over hydrogen evolution, the disparity in the onset potentials of these reactions did not adequately explain the variations in nitrate removal efficiency, which was found to be influenced by material resistance and charge-transfer properties. The rate constants of elementary nitrate reduction steps determined from the time-dependent concentrations of nitrate and its reduction products (nitrous acid, hydroxylamine, and ammonium) were used to calculate the selectivity and efficiency of hydroxylamine production for each electrode. In turn, these selectivities and efficiencies were correlated with the density functional theory-computed adsorption energies of a key hydroxylamine precursor on different electrodes to afford a volcano-type plot with Ti and Sn at its pinnacle. Thus, this study introduces valuable descriptors and methods for the further screening of electrocatalysts for hydroxylamine generation and the establishment of more environmentally friendly hydroxylamine production techniques utilizing sustainable electricity.
尽管电化学还原硝酸盐作为生产羟胺的方法具有巨大的潜力，但该策略尚未得到充分研究，电极材料类型对这种还原的选择性和效率的影响仍未得到充分探索。为了弥补这一空白，本研究评估了六种金属（Ag、Cu、Ni、Sn、Ti 和 Zn）作为阴极材料，用于电化学还原硝酸盐生成羟胺，结果表明 Sn 对羟胺生成的选择性最高，而 Ti 的相应法拉第效率和能量利用率最高。尽管所有测试的材料都有利于硝酸盐还原而不利于氢气析出，但这些反应的起始电位差异并不能充分解释硝酸盐去除效率的变化，而硝酸盐去除效率受材料电阻和电荷转移特性的影响。通过测定硝酸盐及其还原产物（亚硝酸、羟胺和铵）的浓度随时间的变化，确定了基本硝酸盐还原步骤的速率常数，从而计算出每个电极生成羟胺的选择性和效率。反过来，这些选择性和效率与密度泛函理论计算的关键羟胺前体在不同电极上的吸附能相关联，得到了一个火山型图，其中 Ti 和 Sn 处于顶点位置。因此，本研究为进一步筛选用于生成羟胺的电催化剂以及建立利用可持续电力的更环保的羟胺生产技术提供了有价值的描述符和方法。
