Fabrication and evaluation of [Ru(bpy)2(MPyTMPP)Cl]+-photoelectrocatalyzed TiO2/ITO anode and [Cu(phen)2Cl]+-electrocatalyzed SWCNTs/C cathode for photo-stimulated SO32−/H2O2 fuel cells

• Ru(II)/TiO2/ITO anode shows good photoelectrocatalysis for sulfite oxidation.
• Cu(II)/SWCNTs/C cathode shows excellent electrocatalytic reduction response to H2O2.
• Photoanode is evaluated by using in situ spectroelectrochemical monitoring.
• The photo-stimulated SO32−/H2O2 fuel cell exhibits attractive performance.

An anisomerous ruthenated porphyrin [Ru(bpy)2(MPyTMPP)Cl]+ (designated as Rub2P, bpy = 2,2′-bipyridine and MPyTMPP = 5-(4-pyridyl)-10,15,20-tris(4-metylphenyl)porphyrin) is first applied to the photoelectrocatalytic oxidation of sulfite on a nano-TiO2 modified indium-tin oxide (ITO) electrode. The Rub2P/TiO2/ITO electrode shows a pair of well-defined redox peaks and good linear electrocatalytic response toward the oxidation of sulfite between 0.02 and 10.0 mM. Both absorption and emission of Rub2P depleted by an anode potential (+0.9 V vs. Ag–AgCl/0.05 M NaCl) are found to be effectively restored by the electrocatalytic oxidation of sulfite. A [Cu(phen)2Cl]+/SWCNTs/C electrode (phen = 1,10-phenanthrothine, SWCNTs = single-walled nanotubes and C = graphite) is also fabricated, showing an excellent linear electrocatalytic reduction response to H2O2 between 0.05 and 1.0 mM. On the basis of photoelectrocatalysis of Rub2P and electrocatalysis of [Cu(phen)2Cl]+, a photo-stimulated SO32−/H2O2 fuel cell with a saturated KCl salt-bridge is elaborately assembled. The proposed hybrid fuel cell upon 0.1 mW cm−2 UV light has attractive performances, which indicate open-circuit photovoltage (Voc) of 0.612 V, short-circuit photocurrent (Isc) of 153.96 μA cm−2 and maximum power density (Pmax) of 33.55 μW cm−2 at 0.46 V, fill factor (ff) of 0.36 and photoenergy conversion efficiency (η) of 35.6%, respectively. The results from this study provide an effective method for better designing and building photo-stimulated enzyme-free fuel cells.

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