The effect of operating conditions on the stability of BiVO4 photoelectrodes

The development of photoelectrochemical (PEC) systems for solar fuel production has been focused mainly on the fabrication and study of highly efficient materials. However, when the main target is to increase performance in terms of photocurrent densities, the selection of operating conditions becomes inconsistent due to ad hoc approaches preferred by researchers to maximise photocurrent densities at the expense of stability, scalability and practical application. The operating conditions for increased stability and for improved solar-to-fuel efficiency are usually at odds. For example, BiVO4 photoelectrodes report higher stability when used in near-neutral electrolytes, although photocurrent densities are higher when alkaline electrolytes are used. Similarly, chronoamperometries performed at low electrode potentials usually register more stable, although lower, photocurrent densities compared to those at high electrode potentials. For BiVO4 photoelectrodes, the effect of different operating condition has been studied separately, e.g. irradiance, temperature and pH, although with a focus on performance instead of stability. More recently, the authors decoupled the effect of increased irradiance and temperature on the dissolution of BiVO4 by examining the competing behaviour between these two factors. However, the effect of other relevant operating conditions such as electrolyte concentration, pH, electrode potential and electrolyte flow, and their interactions, has yet to be reported.