Catalyst concentration, ethanol content and initial pH effects on hydrogen production by photocatalytic water splitting.

• Pd-TiO 2 /ZSM-5 catalyst was used in water splitting under UV light. • Empirical models were obtained for effects of operational conditions on H 2 production rate. • H 2 production was mainly affected by catalyst concentration and ethanol content. • Initial pH presented negative effect on photocatalytic H 2 production. Operational variables effects on hydrogen production in photocatalytic water splitting system were evaluated using Pd-TiO 2 /ZSM-5. This material was synthetized and had its physicochemical properties properly characterized. Using experimental design techniques allowed the simultaneous evaluation of the effects of catalyst concentration, ethanol (sacrificial reagent) content and initial solution pH on hydrogen production rate. It was verified that an increase in catalyst concentration or ethanol content has a positive influence on system productivity until a maximum point is reached, from which a decrease on gas evolution rate occurs. In contrast, an increase in the initial solution pH presented a linear negative effect on hydrogen production in all analyzed experimental region. Among evaluated conditions, the highest total hydrogen production rate, 712 μmol h−1 (791 μmol g cat −1 h−1), was obtained using a catalyst concentration of 1.5 g L−1, a 16% ethanol content and initial solution pH equal to 4. [ABSTRACT FROM AUTHOR]