Pulsed Electrocatalysis Enabling High Overall Nitrogen Fixation Performance for Atomically Dispersed Fe on TiO₂

Abstract

Atomically dispersed Fe was designed on TiO2 and explored as a Janus electrocatalyst for both nitrogen oxidation reaction (NOR) and nitrogen reduction reaction (NRR) in a two‐electrode system. Pulsed electrochemical catalysis (PE) was firstly involved to inhibit the competitive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Excitingly, an unanticipated yield of 7055.81 μmol h−1 g−1cat. and 12 868.33 μmol h−1 g−1cat. were obtained for NOR and NRR at 3.5 V, respectively, 44.94 times and 7.8 times increase in FE than the conventional constant voltage electrocatalytic method. Experiments and density functional theory (DFT) calculations revealed that the single‐atom Fe could stabilize the oxygen vacancy, lower the energy barrier for the vital rupture of N≡N, and result in enhanced N2 fixation performance. More importantly, PE could effectively enhance the N2 supply by reducing competitive O2 and H2 agglomeration, inhibit the electrocatalytic by‐product formation for longstanding *OOH and *H intermediates, and promote the non‐electrocatalytic process of N2 activation.

Material descriptors for thermoelectric performance of narrow-gap semiconductors and semimetals

“…Guo et al recently reported experimentally measured zT 300 K of 0.2 without optimizing the carrier concentration. 85 The highest zT of the material was found to be 1.3 at 673 K.…”

Oxygen Vacancies‐Rich Metal Oxide for Electrocatalytic Nitrogen Cycle

“…Ding et al synthesized atomically dispersed Fe loaded on TiO 2 (Fe–TiO 2 ) via hydrothermal reaction ( Figure 12 a). [ 106 ] The introduction of Fe increases the concentration of Ov, and the average valence state of Fe is between Fe 2+ and Fe 3+ (Figure 12b). Figure 12c describes the mechanism of NOR process, and the activation of N 2 to produce * NN(OH) is the underlying determining step, just ≈2.99 eV input is required to start this reaction over Fe–TiO 2 surface, lower than that over TiO 2 (4.23 eV).…”

Controlling the Metal–Ligand Coordination Environment of Manganese Phthalocyanine in 1D–2D Heterostructure for Enhancing Nitrate Reduction to Ammonia

“…Nitrogen in nitrate ions has an oxidation state of +5, which can form a number of nitrogenous products in oxidation states from +3 to −3, including nitrite (+3, NO 2 – ), nitric oxide (+2, NO), nitrous oxide (+1, N 2 O), nitrogen (0, N 2 ), hydroxylamine (−1, NH 2 OH), hydrazine (−2, N 2 H 4 ), and ammonia (−3, NH 3 ). ,− Development of numerous electrocatalytic systems using a variety of heterogeneous catalysts including Cu, Ag, Au, Rh, Ru, Ir, Pd, Pt, etc. often converts NO 3 – to N 2 via a five-electron transfer process. − Several research groups have also shown that electrochemically NO 3 – can be converted to hydroxylamine, nitrite, and hydrazine. − Electrocatalytic nitrate to ammonia conversion [NO 3 – + 6H 2 O + 8e – → NH 3 + 9OH – ] via an eight-electron transfer process using metal, nonmetal, and transition-metal-based electrocatalysts would be an alternative option for next-generation ammonia production. − The selectivity toward ammonia synthesis was unsatisfactory, and generally a broad range of products is obtained. This is due to the complexity of the process, strong competition from HER, and the production of various byproducts, which reduce the faradaic efficiency (FE) and selectivity of ammonia .…”