The
electrochemical oxidation of sulfite ions offers encouraging
advantages for large-scale hydrogen production, while sulfur dioxide
emissions can be effectively used to obtain value-added byproducts.
Herein, the performance and stability during sulfite electrolysis
under alkaline conditions are evaluated. Nickel foam (NF) substrates
were functionalized as the anode and cathode through electrochemical
deposition of palladium and chemical oxidation to carry out the sulfite
electro-oxidation and hydrogen evolution reactions, respectively.
A combined analytical approach in which a robust electrochemical flow
cell was coupled to different in situ and ex situ measurements was successfully implemented to monitor
the activity and stability during electrolysis. Overall, satisfactory
sulfite conversion and hydrogen production efficiencies (>90%)
at
10 mA·cm–2 were mainly attributed to the use
of NF in three-dimensional electrodes with a large surface area and
enhanced mass transfer. Furthermore, stabilization processes associated
with electrochemical dissolution and sulfur crossover through the
membrane induced specific changes in the chemical and physical properties
of the electrodes after electrolysis. This study demonstrates that
NF-based electrocatalysts can be incorporated in an efficient electrochemical
flow cell system for sulfite electrolysis and hydrogen production,
with potential applications at a large scale.