Visible electroluminescence (EL) from cathodically biased n-Si in an electrolyte solution containing S2O82- has been studied. EL from the porous n-Si samples fabricated by photoelectrochemical etching over a wide range of current densities (J(a)) shows both blueshift and peak broadening with increasing J(a), which can be attributed to the progressive participation of more silicon hydride species, Si-H-n, with larger n in the emitting progress. Based on analysis of spectral changes and resolution of the EL peak into components, a revised mechanism of the EL, where silicon hydrides are considered to donate electrons to sulfate radical anions, is proposed. EL is produced by recombination of the resulting radical, Si-H-n(+), with an accumulated electron in the conduction band. The radicals would lead to competing reactions that strip off hydrogens from the surface silicon hydrides. Si-H-n with larger n is subject to the earlier EL.