Efficient Nitrate Conversion to Ammonia on f-Block Single-Atom/Metal Oxide Heterostructure via Local Electron-Deficiency Modulation

Abstract

Exploring single-atom catalysts (SACs) for the nitrate reduction reaction (NO3 –; NitRR) to value-added ammonia (NH3) offers a sustainable alternative to both the Haber–Bosch process and NO3 –-rich wastewater treatment. However, due to the insufficient electron deficiency and unfavorable electronic structure of SACs, resulting in poor NO3 –-adsorption, sluggish proton (H*) transfer kinetics, and preferred hydrogen evolution, their NO3 –-to-NH3 selectivity and yield rate are far from satisfactory. Herein, a systematic theoretical prediction reveals that the local electron deficiency of an f-block Gd single atom (GdSA) can be significantly regulated upon coordination with oxygen-defect-rich NiO (GdSA-D-NiO400) support. Thus, facilitating stronger NO3 – adsorption via strong Gd5d–O2p orbital coupling and further improving the protonation kinetics of adsorption intermediates by rapid H* capture from water dissociation catalyzed by the adjacent oxygen vacancy site along with suppressed H* dimerization synergistically boosts the NH3 selectivity/yield rate. Motivated by DFT prediction, we delicately stabilized electron-deficient (strongly electrophilic) GdSA on D-NiO400 (∼84% strong electrophilic sites), which exhibited excellent alkaline NitRR activity (NH3 Faradaic efficiency ∼97% and yield rate ∼628 μg/(mgcat h)) along with superior structural stability, as revealed by in situ Raman spectroscopy, significantly outperforming weakly electrophilic Gd nanoparticles, defect-free GdSA-P-NiO400, and reported state-of-the-art catalysts.

Understanding the role of Ce sites for boosting PEC-NIRR without externally applied potentials

“…8–10 However, in practical PEC-NIRR, the complexity of the 8-electron transfer process and the diversity of high-energy intermediates often cause low selectivity and yield of NH 3 . 11,12 As shown in previous reports, the nature of bulk phase and surface has been confirmed as the predominant factor controlling the energy transfer and reaction barrier. Recently, some promising catalysts have been constructed, but there is still a great challenge in the structural tailoring to reach the intrinsic property of PEC-NIRR.…”

Nanorod Array-Based Hierarchical NiO Microspheres as a Bifunctional Electrocatalyst for a Selective and Corrosion-Resistance Seawater Photo/Electrolysis System

“…The Ni 2p spectrum consists of four peaks located at 854.9, 860.4, 872.5, and 878.1 eV assigned to Ni 2p 3/2 , Ni 2p 3/2 satellite, Ni 2p 1/2 , and Ni 2p 1/2 satellite peaks, respectively. 45,46 attributed to metal-O, the peak at ∼530.9 eV can be assigned to metal-OH, and the peak at ∼532.2 eV corresponds to the adsorbed H 2 O contribution. The observed results are entirely compatible with previous reports on nickel oxy/hydroxide.…”

“…The formation of the NiO structure is verified by the binding energies of high-resolution Ni 2p and O 1s spectra. The Ni 2p spectrum consists of four peaks located at 854.9, 860.4, 872.5, and 878.1 eV assigned to Ni 2p 3/2 , Ni 2p 3/2 satellite, Ni 2p 1/2 , and Ni 2p 1/2 satellite peaks, respectively. , Figure c displays the XPS profile of O 1s, in which the peak centered at ∼531 eV can be deconvoluted into three peaks: the peak at ∼529.4 eV is attributed to metal-O, the peak at ∼530.9 eV can be assigned to metal-OH, and the peak at ∼532.2 eV corresponds to the adsorbed H 2 O contribution. The observed results are entirely compatible with previous reports on nickel oxy/hydroxide …”

Multifunctional Na-enriched Ni–Fe/Ni–P plates for highly efficient photo- and electrocatalytic water splitting reactions

“…71 Sodium entrapped in the entire system could generate oxygen vacancies that significantly enhanced the OER activity as the doping of cation (sodium) or anion could generate oxygen vacancies. [37][38][39][40][41] Furthermore, NiP existing in the system acts as an excellent charge carrier as well as a functional substrate. On NiP, phosphide-oxide or phosphide hydroxide interface layers are formed when it is in contact with water molecules that maintain the continuous charge transfer.…”

“…[32][33][34] Recent reports in the literature have evidenced that in sodium-incorporated Ni-based catalyst systems, faster electron transfer occurs than in sodium-free catalyst systems and also induces the formation of new active sites for photocatalytic reactions. 35,36 Oxygen vacancies play a vital role in the photocatalytic process, [37][38][39][40][41] and the incorporation of sodium metals can also increase the number of oxygen vacancies, which enhance the catalytic process, and in the presence of alkali metals, the formation of oxygen vacancies occurs faster. Sodium-incorporated metal oxides have been reported to show a higher photocatalytic activity due to the formation of oxygen vacancies.…”