The following proposal aims to ellucidate the role of ammonium ions in sulfite oxidation reaction. The key step in the sulfur-ammonia photothermochemical cycle, which is one of the potential processes capable to exploit a pollutant as sulfur dioxide to provide solar hydrogen at large scale and ammonium sulfate, an energy carrier, and a potential fertilizer respectively.Inelastic Neutron Scattering Experiments will be vital to monitor and label deuterated species at different stages of the abovementioned reaction, which in this particular proposal will be electrochemically induced. Thus, in principle, these experiments in tandem with Raman and Nuclear Magnetic Resonance spectroscopy observations will confirm the participation of ammonium as an intermediate during water splitting.