Importance of surface roughness of TiO₂ photoanodes in promoting photoelectrochemical activities with and without sacrificial agent

This paper is intended to highlight the importance of surface roughness of TiO₂ photoanodes in a photoelectrochemical (PEC) cell with and without sacrificial agents. TiO₂ films were synthesized via a spray pyrolysis method in the presence of PEG₂₀₀ as a surface-roughening agent. The rough-surface photoanode led to excellent photo-voltammetric output by doubling the limiting photocurrent of its smooth-surface counterpart (from 0.11 mA/cm² to 0.23 mA/cm² at 0.8 V vs HgO|Hg). The function of glycerol as an anodic sacrificial agent is also exploited more effectively in the use of rough-surface TiO₂. When the smooth-surface TiO₂ is used, the presence of glycerol promotes additional photocurrent densities of as low as 0.037 mA/cm² and 0.043 mA/cm² at −0.7 V vs HgO|Hg and at 0.8 V vs HgO|Hg, respectively. At the same respective potentials, the use of rough-surface TiO₂ gives rise to remarkably higher additional photocurrent density of 0.16 mA/cm² and 0.11 mA/cm² – favoring less anodic potential, that is. Hence, we conclude that surface roughening of the photoanode is an effective, albeit simple, strategy to significantly improve PEC responses and make the most use of anodic sacrificial agents.