Nickel substituted cobalt nanoferrites for advanced photocatalytic and electrocatalytic green hydrogen generation

Green hydrogen emerges as a particularly promising candidate for a sustainable future. It shows large calorific values while also being free of carbon emission. Also, hydrogen production methods like electrocatalysis and photocatalysis could produce hydrogen without the need of fossil fuel and doesn't cause formation of any other harmful gases. Here, we prepared a series of nickel-modified cobalt ferrite nanocatalysts with the composition Co_1-xNi_xFe₂O₄ (x = 0.1–0.5) through sol-gel auto-combustion route to investigate their electro/photo catalytic water splitting characteristics. XRD analysis affirms the spinel cubic phase for the prepared materials, while Rietveld refinement indicates the successful formation of a single-phase system in the developed compositions. The FESEM images of CoNi1 (x = 0.1) and CoNi3 (x = 0.5) specimens reveals the presence of agglomerated grains exhibiting spherical and cubic morphologies. With Ni doping there is an increment in the band gap from 1.75 to 2.11 eV. Raman and XPS studies corroborate the presence of the spinel structure and confirm the elemental states within the nanomaterials. As per photocatalytic analysis, the CoNi3 catalyst attains the highest photocatalytic hydrogen generation of 19.43 mmolg_cat⁻¹ in 8 h. Also, with the increasing Ni doping concentration, there is an increase in overpotential at 10 mA/cm³, which shows that the CoNi2 electrocatalyst have maximum HER electrocatalytic performance. Consequently, due to its remarkable catalytic performance in water splitting, nickel-doped CoFe₂O₄ presents significant advantages for the generation of clean and renewable hydrogen.