3.4% Solar‐to‐Ammonia Efficiency from Nitrate Using Fe Single Atomic Catalyst Supported on MoS2 Nanosheets

Ji Li,Manish Chhowalla,Antoine Tiberj,Eddy Petit,Luc Lajaunie,Lirong Zheng,Huali Wu,Yuan Zhang,Wensen Wang,Ruohan Yu,Chao Liu,Xuechuan Wang,Kun Qi,Damien Voiry,Yang Zhang

doi:10.1002/adfm.202108316

Abstract

AbstractElectrochemical synthesis of NH3 is a carbon‐free alternative to the traditional Haber–Bosch process. Obtaining NH3 from environmental pollutants, such as nitrates or nitrites, is a more practical route than from the nitrogen reduction reaction (NRR) due to the difficult cleavage of the inert triple bond of nitrogen gas. Here, a novel heterogeneous catalyst is reported based on iron (Fe) single‐atoms supported on 2D MoS2 (Fe‐MoS2) for the nitrate reduction reaction (NO3RR). Fe‐MoS2 exhibits remarkable performance with a maximum Faradaic efficiency of 98% for NO3RR to NH3 at an onset potential of −0.48 V versus the reversible hydrogen electrode (RHE) as confirmed by the isotopic nuclear magnetic resonance (NMR) analyses. Density functional theory (DFT) calculations reveal that the enhanced selectivity for the production of NH3 from single Fe atoms supported on MoS2 is attributed to a reduced energy barrier of 0.38 eV associated with de‐oxidation of *NO to *N. The catalysts are coupled to an InGaP/GaAs/Ge triple‐junction solar cell to demonstrate a solar‐to‐ammonia (STA) conversion efficiency of 3.4% and a yield rate of 510 µg h−1 cm−2. The results open new avenues for the design of single‐atom catalysts (SAC) for the realization of solar‐driven ammonia production.

Highlights

Ammonia (NH3) is an important industrial chemical that is widely applied as a nitrogenrich fertilizer for agriculture, textiles, plastics, and the pharmaceutical industry.[1,2] The N cycle perturbation is among the 3 identified planetary boundaries that have already been transgressed by humanity.[3]
For renewable energy and net-zero carbon emission, ammonia has been identified as a promising energy carrier because of its high hydrogen content of 17.7 wt % and its high gravimetric energy density at 3 kWh kg-1.4–7 The synthesis of NH3 via the Haber-Bosch reaction is done under harsh conditions with temperatures and pressures exceeding 400 °C and bar, respectively
The direct electrochemical reduction of N2 for the production of ammonia under mild conditions is severely limited by several bottlenecks such as: i) the high energy barrier required for cleavage of inert N≡N triple bond;[13,14] ii) nonpolar nature of nitrogen molecules that results in a weak interaction between N2 and active sites of catalysts;[15] iii) the very low solubility of N2 in water leading to slow reaction rates.[16,17]

Summary

Introduction

Ammonia (NH3) is an important industrial chemical that is widely applied as a nitrogenrich fertilizer for agriculture, textiles, plastics, and the pharmaceutical industry.[1,2] The N cycle perturbation is among the 3 identified planetary boundaries that have already been transgressed by humanity.[3]. Fe atoms supported on MoS2 nanosheets (Fe-MoS2) for the electrocatalytic NO3RR, which exhibits excellent performance with a Faradaic efficiency of 98 % toward NH3 at a low overpotential of -0.48 V versus the reversible hydrogen electrode (vs RHE) and a cathodic energy efficiency of 31% at vs RHE and -0.28 V vs RHE, respectively.

Results

Conclusion