Outstanding stability and photoelectrochemical catalytic performance of (Fe, Ni) co-doped Co3O4 photoelectrodes for solar hydrogen production

In this work, pure and (Fe, Ni) co-doped Co3O4 nanostructured photoelectrodes of different doping levels and thicknesses were manufactured at constant substrate temperature (450 degrees C) using the spray pyrolysis technique. In addition to the chemical compositions; the structural, optical, electrical, and photoelectrochemical (PEC) properties were investigated through the use of various analysis techniques. By increasing the codpoing ratio to 6%, the low energy band gap is decreased from 1.43 to 1.3 eV and the high energy bandgap is increased from 2.63 to 2.87 eV, in addition to the reduction in particle size from 30.2 to 12.0 nm. The high energy gap vanishes by increasing the codoped film's spread volume to 60 ml. X-ray photoelectron spectroscopy of 6%(Fe, Ni)-60ml Co3O4 confirms the existence of Ni-2+,Ni-3+ and Fe-2+,Fe-3+. Among the studied photoelectrodes, the 6%(Fe, Ni)-60ml Co3O4 photoelectrode displays a photocatalytic hydrogen output rate of 150 mmol/h.cm(2) @-1V in 0.3M Na2SO4 electrolyte. The photocurrent density of 6%(Fe, Ni)-60ml photoelectrode reached up to 13.6 mA/cm(2)@-1V with an IPCE (incident photon to current conversion efficiency) of similar to 42%@405 nm and STH (solar to hydrogen conversion efficiency) of similar to 11.37%, which are the highest values yet for Co3O4-based photocatalysts. The value of ABPE(applied bias photon-to-current efficiency) is 0.34%@(-0.28V and 636 nm). Interestingly, this photoelectrode shows a photogenerated current density of similar to 0.14 mAcm(-2) at 0 V and a PEC current onset over 0.266V. The thermodynamic parameters, corrosion parameters, PEC surface areas, Tafel slopes, and impedance spectroscopies are also being studied to confirm and classify the PEC H-2 production mechanism. The 6%(Fe, Ni)-60ml Co3O4 photoelectrode stability/reusability shows only a 6.6% reduction in PEC performance after ten successive runs at -1V with a corrosion rate of 1.2 nm/year. This work offered a new codoping strategy for the design of a highly active Co3O4 based photocatalyst for the generation of solar light-driven hydrogen. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, nanostructured photoelectrodes of pure and (Fe, Ni) co-doped Co3O4 with varying doping levels and thicknesses were manufactured using the spray pyrolysis technique. By increasing the codoping ratio, the energy band gaps decreased, particle size reduced, and the existence of different elements confirmed. Among them, the 6%(Fe, Ni)-60ml Co3O4 photoelectrode exhibited the highest photocatalytic hydrogen output rate and photocurrent density, displaying promising potential for solar light-driven hydrogen generation.