S-Doped NiII-Triazolate Derived Ni-S-C Catalyst for Electrochemical CO2 Reduction to CO

Metal heteroatom doped carbon materials display remarkable catalytic performance in the electrochemical CO2 reduction (ECR) because the doped heteroatoms can significantly change the local density of state and electronic structure of carbon, which induces charge polarization or structural defects. Herein, we synthesized S-doped NiII-triazolate precursors with high purity and crystallinity through a simple one-step hydrothermal method. The high-temperature pyrolysis process produced a series of Ni-S-CT (T = 800, 900, 1000 degrees C) materials with Ni3S2 as the main component. It resulted in significant carbon structure defects in the catalyst, which increased the specific surface area and pore volume, providing a basis for improving the ECR activity. Through the structural characterizations of powder X-ray diffraction (PXRD), Raman, X-ray photoelectron (XPS), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), and electrochemical characterizations of linear sweep voltammetry (LSV), chronoamperometry (i-t curve), electrochemical impedance spectroscopy (EIS), and electrochemical active surface area (ECSA), as well as gaseous product analysis, we can build the structural-performance relationship. Ni-S-CT catalysts all reached the highest CO Faraday efficiency at -1.5 V vs Ag/AgCl potential, among which Ni-S-C1000 exhibited the best catalytic activity (FECO of 66.6% and jCO of 1.28 mA/ cm2). It also displayed excellent stability and recyclability, which could realize the efficient reuse of the catalyst. In addition, the density functional theory (DFT) calculation was carried out on Ni3S2 to illustrate the ECR activity origination. It is the first report on Ni3S2-based catalysts in the application of ECR.

Automated summary

Metal heteroatom doped carbon materials show remarkable catalytic performance in the electrochemical CO2 reduction due to changes in the local density of state and electronic structure of carbon. S-doped NiII-triazolate precursors were synthesized, and pyrolysis produced Ni-S-CT materials with Ni3S2 as the main component, resulting in carbon structure defects that improve the catalytic activity. Ni-S-C1000 exhibited the best activity with high CO Faraday efficiency and stability. Density functional theory calculations on Ni3S2 were performed to understand the origin of the catalytic activity.