Ni–Mo modified metal–organic frameworks for high-performance supercapacitance and enzymeless H2O2 detection

Abstract

In this work, we synthesized A(B)-Ni_xMo_y-MOFs@AAC hybrids with different molar ratios of nickel and molybdenum through a liquid phase method and a hydrothermal method. The irregularly shaped Ni/Mo nanoparticles are closely anchored on the surface of the MOFs and the A(B)-Ni_xMo_y-MOFs are supported on the acidified activated carbon (AAC) with a size of ∼6 nm. Interestingly, the MOF particles are hexahedral under mild liquid conditions and present a cubic shape under hydrothermal conditions. The A(B)-Ni_xMo_y-MOFs@AAC hybrids were tested using transmission electron microscopy (TEM), contact angle measurements, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analytical techniques. The prepared A(B)-Ni_xMo_y-MOFs@AAC hybrids were then used as electrode materials. In particular, the A(B)-Ni₁Mo_0.5-MOFs@AAC electrode exhibited excellent electrochemical properties, with a high specific capacitance (1178 F g⁻¹ at 0.5 A g⁻¹ for the A-Ni₁Mo_0.5-MOFs@AAC electrode and 1145.7 F g⁻¹ at 0.5 A g⁻¹ for the B-Ni₁Mo_0.5-MOFs@AAC electrode), and exceptional stability (83.40% maintenance of specific capacitance for the A-Ni₁Mo_0.5-MOFs@AAC electrode and 78.31% maintenance for the B-Ni₁Mo_0.5-MOFs@AAC electrode at 15 A g⁻¹). Meanwhile, the as-obtained A(B)-Ni₁Mo_0.5-MOFs@AAC//AAC achieved a high energy density of 85.83 W h kg⁻¹ to 54.05 W h kg⁻¹ (A-Ni₁Mo_0.5-MOFs@AAC//AAC) and from 68.26 to 36.07 W h kg⁻¹ (B-Ni₁Mo_0.5-MOFs@AAC//AAC) based on the total mass of active material at a current density in the range of 1 to 25 A g⁻¹. In addition, the A(B)-Ni_xMo_y-MOFs@AAC hybrids were also employed as nonenzymatic sensors for the electrochemical detection of H₂O₂, and exhibited high sensitivity (0.277 μA μM⁻¹ for the A-Ni₁Mo_0.5-MOFs@AAC sensor and 0.188 μA μM⁻¹ for the B-Ni₁Mo_0.5-MOFs@AAC sensor) and noteworthy low detection limits of 0.185 and 0.303 μM based on 3 signal–noise ratios, respectively. Therefore, we expect that the A(B)-Ni₁Mo_0.5-MOFs@AAC electrodes as electrode materials would have potential applications in supercapacitors and the nonenzymatic detection of H₂O₂.