Energy Efficiency in Photocatalytic Reactors for the Full Span of Reaction Times

Abstract

OH • radicals react in photocatalytic reactors via adsorbed species on the catalytic surface through complex reaction mechanisms leading to complete mineralization of organic molecules. Our research group has recently contributed with kinetic modeling of the photocatalytic network using a parallel-series reaction network. This kinetic approach helps toward the assessment of the photocatalytic thermodynamic efficiency factors (PTEF) and quantum yields (QY). Efficiency calculations consider stoichiometric relationships involving observable chemical species and OH • groups. These stoichiometric equations set the OH • requirements for reaching a particular intermediate species and for the complete mineralization of them. On this basis, the PTEF and QY factors for phenol photoconversion point toward a high degree of photon utilization as in the case of Photo-CREC units and, as a result, confirm the value of photocatalysis for the conversion of organic pollutants in water.

Efficiency Factors in Photocatalytic Reactors: Quantum Yield and Photochemical Thermodynamic Efficiency Factor

“…In this respect, if one would like to analyze mechanisms in photocatalysis using QY s, it should be checked that the QY s do not surpass the QY max = 1.33 upper limit, with this being in compliance with the overall 1 vacant site/1 electron mechanism. It is interesting to notice that this stoichiometric limit for QY or QY max is an observed constraint for the photocatalysis of organic pollutants both in air and water, as reported by Garcia Hernandez et al 20 and Serrano et al 21.…”

“…In this context, there are a number of studies that consider photocatalytic efficiencies, however, with significant differences in their definitions 7–21. For instance, one could use the empirical/semi‐empirical factors, such as the electrical energy per order (EE/O) for efficiency calculations.…”

“…Consequently, by including Eqs. 45–47 in the analysis of chemical species adsorption phenomena, the total consumption rate of OH • radicals can be alternatively represented at any time during irradiation as follows 21: …”

Photocatalytic degradation of malic acid using a thin coated TiO2‐film: Insights on the mechanism of photocatalysis

“…The apple juice was tested using the Photo‐CREC Water‐II. This reactor unit has been previously used for photodegradation of organic compounds in water treatment showing its high quantum efficiency . However, Photo‐CREC Water II reactor is not adequate for opaque fluids.…”

“…The methodology reported by Serrano et al was used to calculate the quantum yield for RN2. This methodology uses the RN along with the stoichiometric amount of hydroxyl radicals required in each reaction step.…”