Electrocatalytic Reduction of Nitrate to Ammonia on Low-Cost Ultrathin CoO_x Nanosheets

Abstract

The electrochemical nitrate reduction reaction (NITRR) is an appealing method for ammonia synthesis, owing to the ambient conditions as well as its abundant sources, low dissociation energy, and high solubility of nitrate. The hydrogen evolution reaction is a competing process of the NITRR, which should be properly suppressed to achieve a high Faradaic efficiency of the NITRR. Herein, ultrathin CoO x nanosheets with abundant surface oxygen are designed as a low-cost NITRR catalyst, which delivers an ultrahigh ammonia yield of 82.4 ± 4.8 mg h −1 mg cat −1 with a Faradaic efficiency of 93.4 ± 3.8% at −0.3 V versus the reversible hydrogen electrode. Theoretical calculation reveals that the surface oxygen on cobalt sites can stabilize the adsorbed hydrogen on cobalt oxide, which hampers the evolution of hydrogen and leads to an enhanced NITRR activity. This work demonstrates that surface modification plays a critical role in suppressing the HER and facilitating the NITRR through a NHO pathway with a lower energy barrier.

Ultrahigh oxygen evolution reaction activity in Au doped co-based nanosheets

“…2c . 26,27 MA of Au–Co(OH) 2 is 177 A g −1 , which is much higher than 3.89 A g −1 , 7 A g −1 , 22.56 A g −1 , and 5.66 A g −1 of Co(OH) 2 , Co 3 O 4 , CoOOH, and IrO 2 , respectively. The TOF of Au–Co(OH) 2 is 27 s −1 , which is much higher than 0.6 s −1 , 1.07 s −1 , 3.45 s −1 , and 0.87 s −1 of Co(OH) 2 , Co 3 O 4 , CoOOH, and IrO 2 , respectively.…”

Enhanced electrocatalytic nitrate reduction to ammonia using plasma‐induced oxygen vacancies in CoTiO3 − x nanofiber

“…Supporting Information: Figure S2 shows the Co 2p spectrum, with four peaks around 780.0, 781.5, 796.5, and 798.6 eV correspond to Co 3+ 2p 3/2 , Co 2+ 2p 3/2 , Co 3+ 2p 1/2 , and Co 2+ 2p 1/2 , respectively. [43,44] Ti 2p spectrum (Supporting Information: Figure S3) is divided into four peaks at 457.4, 458.9, 463.1, and 464.6 eV, assigning to Ti 3+ 2p 3/2 , Ti 4+ 2p 3/2 , Ti 3+ 2p 1/2 , and Ti 3+ 2p 1/2 , respectively. [45] In O 1s region of CoTiO 3 and CoTiO 3 − x (Figure 1h), the binding energies at 529.8 and 532.03 are attributed to the lattice oxygen and V O , respectively.…”

Interfacial engineering of Cu–Fe2O3 nanotube arrays with built-in electric field and oxygen vacancies for boosting the electrocatalytic reduction of nitrates

“…31 In addition, as the most basic form of defect, OVs have been widely used in the ENRA field. [32][33][34][35] For example, OVs in TiO 2 can not only capture nitrate and weaken N-O bond energy, but also inhibit the generation of by-products, thus significantly improving the efficiency of electrocatalytic ammonia production. 36 OVs in the amorphous RuO 2 phase effectively regulates the d-band center and hydrogen affinity, thereby reducing the energy of the potentialdetermination step.…”