Multicomponent TiO₂/Ag/Cu₇S₄@Se Heterostructures Constructed by an Interface Engineering Strategy for Promoting the Electrocatalytic Nitrogen Reduction Reaction Performance

Abstract

The electrocatalytic nitrogen reduction reaction (ECNRR) is a sustainable and environmentally friendly method for NH 3 synthesis under environmental conditions relative to the Haber−Bosch process; however, its low selectivity (Faradaic efficiency (FE)) and low NH 3 yield impede the progress. Herein, benefiting from the application of the interface engineering strategy, a multicomponent TiO 2 /Ag/Cu 7 S 4 @Se-CC heterogeneous electrocatalyst with a unique structure was successfully fabricated, generating a unique sandwich structure by using a Ag layer as an electric bridge intercalated between TiO 2 and Cu 7 S 4 , in which the optimized catalyst can accelerate the electron transfer efficiency. Moreover, through the electronic structure adjustment, an electron-deficient region was constructed, which can inhibit the H 2 adsorption but enhance the N 2 adsorption, thereby improving the selectivity and the catalytic activity. Significantly, the FE and NH 3 yield of TiO 2 /Ag/Cu 7 S 4 @Se-CC reached 51.05 ± 0.16% and 39.16 ± 2.31 μg h −1 cm −2 , in which the FE is among the highest non-precious metalbased NRR electrocatalysts in alkaline electrolytes reported. This study provides insight into the rational design and construction of NRR electrocatalysts for electrocatalytic applications.

Cu2+1O/Ag Heterostructure for Boosting the Electrocatalytic Nitrate Reduction to Ammonia Performance

“…41,42 In contrast to the peak displacement of Cu, the main peak of Ag moves toward the high binding energy, indicating that Ag is the electron donor. 35,40 To further indicate the valence state in which the copper element is located, a Cu LMM (a transition form producing the Auger spectrum) Auger spectrum test was performed, as shown in Figure S4, where the peak appearing at 570 eV is attributed to Cu + , while the presence of Cu 0 was not observed, 43,44 being consistent with the XRD results. The peak at 573.1 eV represents different transition states of the Cu LMM spectrum.…”

“…31,39 After forming a heterogeneous interface by introducing Ag, the peak position of the Cu 2p orbital is shifted, while the peak of Cu is shifted toward the lower binding energy, indicating that Cu is the electronic acceptor. 35,40 The satellite peak of Cu 2p can be mounted at 944.1 eV. The Ag 3d spectra of Cu 2+1 O/Ag-CC, Cu 2+1 O-CC, and Ag-CC are given in Figure 2c, where the XPS spectrum can be decomposed into two peaks centered at 374.1 and 368.05 eV, which are attributed to Ag 3d 3/2 and Ag 3d 5/2 , respectively.…”

“…As shown in Figure S3, the XPS survey spectra of Cu 2+1 O/Ag-CC show the presence of Cu, Ag, and O elements, which is consistent with the energy-dispersive spectrometry energy spectra results. Figure b shows the high-resolution Cu 2p spectra of Cu 2+1 O/Ag-CC, Cu 2+1 O-CC, and Ag-CC, where for Cu 2+1 O/Ag-CC and Cu 2+1 O-CC, the XPS spectra can be deconvoluted into two peaks centered at 934.7 and 932.7 eV, assigned to Cu 2+ and Cu + or Cu 0 , respectively. , After forming a heterogeneous interface by introducing Ag, the peak position of the Cu 2p orbital is shifted, while the peak of Cu is shifted toward the lower binding energy, indicating that Cu is the electronic acceptor. , The satellite peak of Cu 2p can be mounted at 944.1 eV. The Ag 3d spectra of Cu 2+1 O/Ag-CC, Cu 2+1 O-CC, and Ag-CC are given in Figure c, where the XPS spectrum can be decomposed into two peaks centered at 374.1 and 368.05 eV, which are attributed to Ag 3d 3/2 and Ag 3d 5/2 , respectively. , In contrast to the peak displacement of Cu, the main peak of Ag moves toward the high binding energy, indicating that Ag is the electron donor. , To further indicate the valence state in which the copper element is located, a Cu LMM (a transition form producing the Auger spectrum) Auger spectrum test was performed, as shown in Figure S4, where the peak appearing at 570 eV is attributed to Cu + , while the presence of Cu 0 was not observed, , being consistent with the XRD results.…”

“…To improve the efficiency of electrocatalysis, some strategies have been applied to increase the active sites of the catalysts by regulating the compositions, forming the specific morphologies and structures. Among various strategies, the construction of a heterogeneous interface has been considered as an effective strategy to increase the interfacial electron transfer and electrocatalytic active sites. − For example, Sun and co-workers reported a NO 3 RR electrocatalyst with FeS 2 nanoparticles on a TiO 2 nanobelt array (FeS 2 @TiO 2 ), which showed excellent electrocatalytic activity with a large NH 3 yield of 860 μmol h –1 cm –2 and a high FE of 97.0% in 0.1 M NaOH and 0.1 M NO 3 – . Additionally, it is known that element Ag is a good conductor of electricity and the introduction of Ag can improve the conductivity of the catalyst .…”

Co-Doped Fe3S4 Nanoflowers for Boosting Electrocatalytic Nitrogen Fixation to Ammonia under Mild Conditions

“…The electrochemical impedance spectrum test (Figure S18) was performed on pristine Fe 3 S 4 and Fe 3 S 4 with different Co doping concentrations. The results manifest that 4% Co–Fe 3 S 4 possesses the minimum R t value in comparison with other samples, which imply that faster interfacial charge-transfer characteristics as well as more facile electrode dynamics are achieved in 4% Co–Fe 3 S 4 during the NRR process. − Accordingly, an appropriate amount of doping can accelerate the electron transfer effectively, which is conducive to the enhancement of NRR activity. In order to further study the reasons for the improvement of electrocatalytic ammonia production performance, nitrogen adsorption–desorption test (BET) and electrochemical double capacitance ( C dl ) test of Fe 3 S 4 , 4% Co–Fe 3 S 4 , and 15% Co–Fe 3 S 4 were carried out.…”