FeOOH上掺入Ni和Cu引起的羟基和含氮中间物的共吸附行为实现加速氨氧化反应中的脱氢过程

Modulating the coadsoption of hydroxyl and nitrogenous groups induced by Ni and Cu doping on FeOOH for accelerating dehydrogenation in the ammonia oxidation reaction

氨是一种很有前途的能源载体,由于其高氢含量和无碳的特点,可用于燃料电池,并可作为电解水制氢装置中水的替代氧化底物.然而,人们对氨电氧化反应(AOR)的机理认识不足,且缺乏廉价、高效的AOR催化剂,因而阻碍了氨基能源系统的发展.在这项工作中,我们通过光诱导化学沉淀法合成的新型Ni和Cu共掺杂的多孔FeOOH纳米棒(NiCu-FeOOH)可以作为AOR催化剂,其具有高效的催化活性(阳极电流密度达到10 mA cm^(-2)时执行电压为1.41 V)和在氨碱溶液中优异的稳定性.实验数据和理论计算结果表明,异质的Ni和Cu原子的协同作用使得NiCu-FeOOH表面的Ni和Fe位点表现出更合适的电子结构,他们可以共同吸附含氮中间产物和羟基,并使其吸附自由能位于火山形曲线的顶部,从而加速AOR脱氢.决速步骤的后移(*NH_(2)+*OH形成步骤移至*N_(2)H_(3)+*OH形成步骤)和决速步骤较低的能垒(0.86 eV)揭示了Ni和Cu的共掺策略使FeOOH晶体对催化AOR更具活性.本文创新地提出了涉及含氮中间物和羟基的共吸附反应途径,以更好地描述和模拟AOR过程,这为设计低成本和稳定的AOR催化剂开辟了新的路径.

Owing to its high hydrogen content and carbonfree nature,ammonia is a promising energy carrier used in powering fuel cells and an alternative oxidation substrate to water in electrolytic hydrogen production devices.However,the insufficient mechanistic understanding and the lack of inexpensive and efficient catalysts for the ammonia electrooxidation reaction(AOR)have hampered the development of the ammonia-based energy system.In this work,novel Ni and Cu co-doped porous FeOOH nanorods(NiCu-FeOOH)synthesized by a light-induced chemical precipitation method can serve as the AOR catalyst with efficient catalytic activity(1.41 V at an anodic current density of 10 mA cm^(−2))and enhanced stability in an aqueous ammonia solution.According to the experimental data and theoretical calculation results,the synergistic effect of heterogeneous Ni and Cu atoms makes Ni and Fe sites on the surface of NiCu-FeOOH exhibit a suitable electronic structure to coadsorb nitrogenous intermediates and hydroxyl groups at the top of the volcano plot and thereby accelerate dehydrogenation in the AOR.The backward shift of the rate-determining step(RDS)(*NH_(2)+*OH formation step shifts to*N_(2)H_(3)+*OH formation step)and the lower energy barrier of the RDS(0.86 eV)reveal that the Ni and Cu co-doping makes FeOOH crystals active for the AOR.The coadsorption reaction pathway involved in nitrogenous intermediates and hydroxyl groups has been innovatively proposed to effectively describe and simulate the AOR process,which opens a new horizon to design low-cost and stable AOR catalysts.