Superior overall water splitting performance in polypyrrole photoelectrode by coupling NrGO and modifying electropolymerization substrate

We prepare photoelectrodes with mixed metal oxides (TiO₂-RuO₂), polypyrrole (PPy) and N-doped reduced graphene oxide (NrGO) on titanium (Ti) substrate for overall water splitting and methylene blue degradation during two steps; including a sol–gel deposition of mixed metal oxide (MMO) and electrodeposition of PPy or PPy-NrGO films. The as-prepared photoelectrodes are characterized by physical and photoelectrochemical measurements. Ti/MMO/PPy-NrGO photoelectrode exhibit a considerably photocurrent density of −6.97 mA cm⁻² (at 0 V vs. reversible hydrogen electrode [RHE]) and 12.89 mA cm⁻² (at 1.23 V vs. RHE) for hydrogen and oxygen generations, respectively. However, promotion in the H⁺/H₂ efficiency (40.25%) is about 28 orders of magnitude while in the case of H₂O/O₂ (13.77%) is 10 times. The electrochemical impedance spectroscopy and Mott–Schottky measurements reveal that the simultaneous incorporation of MMO and NrGO nanosheets in PPy coating leads to the lowest charge transfer resistance at the photoelectrode/electrolyte interface and an improvement in charge carrier density.