Efficient Ammonia Electrosynthesis and Energy Conversion through a Zn‐Nitrate Battery by Iron Doping Engineered Nickel Phosphide Catalyst

Abstract

reformed hydrogen as feedstock under harsh conditions. [3] Ambient electrocatalytic N 2 reduction reaction (NRR) has emerged as an attractive alternative for NH 3 production, which however suffers from unsatisfactory Faradaic efficiencies (FE) (mostly <50%) and very low NH 3 partial current densities (mostly <1 mA cm -2 ) due to extremely stable triple NN bond (941 kJ mol -1 ) and low N 2 solubility. [4,5] Nitrate reduction into NH 3 (NO 3 -RR) is considered as a promising alternative with large attainable yields owing to the high solubility of NO 3 and low NO bond energy (204 kJ mol -1 ). [6] Furthermore, NO 3 is one of the most widespread groundwater pollutants in the world due to the discharge of industrial wastewater, livestock excrements, and chemical fertilizers, imposing a threat to the health of human beings. [7] Therefore, it is highly attractive to harness NO 3 contaminants to produce the value-added NH 3 from the energy and environmental perspectives.In addition to the chemicals, electricity is one other key pillar of human society. [8][9][10][11][12][13][14][15][16] Notably, the NO 3 -RR involves proton-assisted eightelectron transfer process and its equilibrium potential is 0.69 V versus the reversible hydrogen electrode (RHE), higher than the 0.4 V of the oxygen reduction reaction in Zn-air/oxygen batteries. [17] It is thus highly attractive to combine the NO 3 -RRbased cathode with metal anode as a galvanic cell for electricity production. Such metal-NO 3 battery as a "killing three birds with one stone" strategy is capable of energy supply, ammonia production, and removal of pollutant in ground water. As some possible byproducts such as nitrite and hydrazine may lower the efficiency of such battery, catalyst cathodes with high NH 3 selectivity is highly desired for practical use. [18][19][20] First row transition metal phosphides, as alloy materials of metal and phosphorus, are active catalysts in hydrotreating (HDX, X = S, O, N) and hydrogenation reactions. [21,22] The metal centers in phosphides with partial positive charge can adsorb nitrate and nitrite anions effectively while the partial negative charge centers, i.e., phosphorus, are the proton-acceptor centers. [23] Further, heteroatom doping can well modulate the electronic structure of the catalyst and boost the catalytic activity. [24] The The electrocatalytic nitrate reduction reaction (NO 3 -RR) to ammonia (NH 3 ) offers a promising alternative approach for NH 3 production and nitratebased voltaic cells which can deliver both electricity and NH 3 as products, are also highly attractive. However, nitrate-to-NH 3 conversion involves a proton-assisted multiple-electron transfer process with considerable kinetic barrier, underlying the need for efficient catalysts for the NO 3 -RR. A Zn-nitrate battery is reported to enable a "killing three birds with one stone" strategy for energy supply, ammonia production and removal of pollutants with the iron doped nickel phosphide (Fe/Ni 2 P) as a NO 3 -RR catalyst electrode. Iron doping induces a d...

Recent advances in nanostructured heterogeneous catalysts for N-cycle electrocatalysis

“…Co2AlO4/CC 0.1 M PBS + 0.1 M NaNO3 Yield: 7.9 mg•h −1 •cm −2 , FE: 92.6% [415] Co-Fe@Fe2O3 0.1 M Na2SO4 + 500 ppm NO3 − Yield: 880.52 μg•h −1 •cm −2 , FE: 85.23%, selectivity of 94% [446] Fe-Co3O4 0.1 M PBS + 50 ppm NO3 − Yield: 0.624 mg•h −1 •mgcat. −1 , FE: 95.5% [411] Fe3O4/SS 0.1 M NaOH + 0.1 M NaNO3 Yield: 10,145 μg•h −1 •cm −2 , FE: 91.5% [421] Fe/Ni2P 0.2 M K2SO4 + 50 × 10 −3 M NO3 -Yield: 4.17 mg•h -1 •cm -2 , FE: 94.3% at −0.4 V [447] NiFe2O4/CC 0.1 M PBS + 0.1 M NaNO3 Yield: 10.6 mg•h -1 •cm -2 , FE: 96.6% [448] a Ru-ST-5: strained Ru nanoclusters; PA-RhCu cNCs: polyallylamine functionalized frame-like concave RhCu bimetallic nanocubes; Co-NAs: Co nanoarrays; Fe-cyano NSs: Fe-based cyano-coordination polymer nanosheets; TiO2−x: TiO2 nanotubes with oxygen vacancies; pCuO-5: CuO plasmatreated for 5 min; Co/CoO NSAs: Co/CoO nanosheet arrays.…”

A Zn–nitrite battery as an energy-output electrocatalytic system for high-efficiency ammonia synthesis using carbon-doped cobalt oxide nanotubes

“…13 It is worth noting that the reductions of NO 2 − and NO 3 − have the most positive potentials, which are considered as the potentially cathodic reaction to assemble an energy-output electrocatalytic system. 5,14 However, the predominant product of NO 3 − reduction at low potentials is a two-electron reduction product, NO 2 − , and the competing HER occurs at high potentials, which would lower the performance of NH 3 production and the efficiency of the batteries. 15 Notably, NO 2 − possesses the highest solubility in water and its reduction (NO 2 − + 8H + + 6e = NH 4 + + 2H 2 O) has the highest reduction potential calculated to be 0.897 V vs. RHE at pH 0.…”

“…13 It is worth noting that the reductions of NO 2 À and NO 3 À have the most positive potentials, which are considered as the potentially cathodic reaction to assemble an energy-output electrocatalytic system. 5,14 However, the predominant product of NO 3 À reduction at low potentials is a two-electron reduction product, NO 2…”

Controlled Growth of the Interface of CdWOx/GDY for Hydrogen Energy Conversion

“…As shown in Figure 5f + could be observed with the electrolyte after 1h electrolysis under −1.0 V versus SCE using CdWO x /GDY as the cathode in an H-type cell. Moreover, isotopic labeling tests of 15 NO 3 were conducted (Figure 5h), confirming the generated NH 3 originated from the reduction of the nitrates from water rather than other contaminations. The long-term durability of the CdWO x /GDY in the system was evaluated with consecutive electrolysis cycles.…”