Zeolitic imidazolate framework ZIF-67 grown on NiAl-layered double hydroxide/graphene oxide as cathode catalysts for oxygen reduction reaction in microbial fuel cells

In this study, the cathode catalysts for microbial fuel cells (MFCs) were successfully synthesized by two-step feeding method. NiAl-layered double hydroxide (LDH) nanoparticle was attached efficiently on the surface of graphene oxide (GO) in situ, zeolitic imidazolate framework (ZIF-67) was modified on LDH surface layer; Highly crystalline NiAl-LDH/GO@ZIF-67 composite was flawlessly prepared, nano-hybrid had (003), (006), (011), (112) and (222) characteristic crystal planes attribute to NiAl-LDH/GO and ZIF-67 by X-ray diffraction (XRD), and the sheet-like structure and polyhedral structure were observed. The NiAl-LDH/GO@ZIF-67 nano-hybrid was rich in metal elements and provides a wealth of electrochemical active sites by EDS test. The study displayed that the maximum output voltage of NiAl-LDH/GO@ZIF-67-MFC was 516 mV and the stabilization time could last for about 8 d. The maximum output power was 501.26 mW/m², which was 1.31 times of NiAl-LDH/GO-MFC (381.92 mW/m²) and 2.76 times of ZIF-67-MFC (181.48 mW/m²). The GO with high conductivity was used as the substrate to ensure the stability of electrode cycle and the efficiency of power generation, the laminar structure of NiAl-LDH provided the specific surface area for the reaction, which facilitated the transport of electrons. The good structure of ZIF-67 increased the active sites of the composite. The excellent properties of the composites promoted the electrochemical stability and electricity production output of MFC. This study provided a method for the further application of MFC in the wastewater field.