Selective optimisation of catalytic activity by tuning the structural composition in nanoparticulate CuFe2O4

The tailored development of highly active and selective electrocatalysts based on abundant and non-toxic elements will be key to the rigorous implementation of sustainable processes in industry. In this context, spinel-type CuFe2O4 is regarded as a promising candidate. We synthesised CuFe2O4 nanoparticles with various Cu:Fe ratios via a microwave-assisted solvothermal route. The compositional effect on the material properties and performance in multiple electrochemical reactions, including HER, OER, ORR and CO2RR, is investigated, in order to obtain valuable insights about those parameters that drive the improvement of catalytic activities. An increase in lattice strain and surface area is observed for compositions deviating from the ideal 1:2 stoichiometry, which goes in hand with an improved performance in alkaline water splitting. For the CO2RR on the other hand, the Cu-content is determined to be the most important factor, with a Cu-excess being highly beneficial. The suitability of CuFe2O4 as a bifunctional water splitting catalyst was demonstrated by full cell measurements using the spinel catalyst at both the anode and cathode side at the same time. Moreover, we showed the applicability of CuFe2O4 in bifunctional gas-diffusion electrodes for rechargeable Zn-air batteries.