# Highly Active under VIS Light M/TiO\({}_{2}\) Photocatalysts Prepared by Single-Step Synthesis
## 3 Results and Discussion
### N\({}_{2}\) Absorption Studies  
The porosity and the specific surface area are of high importance for materials used as substrates. For that purpose, the three different titania substrates and the samples 0.1 Cu/TiO\({}_{2}\) (R), 0.25 Cu/TiO\({}_{2}\) (R), 0.5 Cu/TiO\({}_{2}\) (R), and 0.25 Cu/TiO\({}_{2}\) (A) were subjected to N\({}_{2}\) physisorption tests at \(-\)195.850 \({}^{\circ}\)C. The Brunauer-Emmett-Teller (BET) method was used for the specific surface area, pore volume, and pore size determination, and Barrett, Joyner, and Halenda (BJH) absorption was used for pore distribution determination.  
All the obtained isotherms were similar to the one that is described in Figure 5b. There are six types of isotherm curves according to the IUPAC classification: ones that are typical of microporous adsorbents (type I), nonporous or macroporous adsorbents (types II, III, and VI), or mesoporous adsorbents (types IV and V). According to that classification of the porous material isotherms [39; 40], this type of isotherm has the same shape as type II isotherms (Figure 5a) that are complex in nature to obtain information about the pore morphology [41]. In this type of isotherms of combined micro-/mesoporous adsorbents, the interactions which are involved are due to the combination of adsorbent-adsorbate and adsorbate-adsorbate interactions.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Photocatalysts’ Name** & **Metal** & **Metal Loading, wt\%** & **Substrate Composition** & \multicolumn{2}{c}{**Metal Concentration**} \\  & & & & **Determined by XRF, ppm** \\ \hline  
\hline \hline \end{tabular}
\end{table}
Table 1: List of as-prepared photocatalysts and their metal loading determined by XRF.  
The adsorption hysteresis curves are also empirically classified by IUPAC. It is widely accepted that there is a correlation between the shape of the hysteresis loop and the pore geometry of a mesoporous material. The hysteresis loop of our materials suggests the existence of cylindrical pores.  
The specific surface area, the cumulative pore volume, and the pore size are summarized in Table 2 for all measured samples.  
It appears that there are no major changes in the specific surface area (SSA) values of the derived photocatalysts, and these values are similar to their corresponding substrate. This can be attributed to the synthetic route that was employed and the small metal concentration in the resulting material. Titania rutile has the lowest SSA (4.38 m\({}^{2}\)/g), while anatase exhibits the highest value (9.93 m\({}^{2}\)/g). It is also observed that increasing the metal loading from 0.1 to 0.5 results in an increase in the average pore diameter.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Sample Name**} & **BET** & **BJH Adsorption Cumulative** & **Adsorption Average Pore** \\  & **m\({}^{2}\)/g** & **Pore Volume, cm\({}^{3}\)/g** & **Diameter, Å** \\ \hline TiO\({}_{2}\)—Anatase & 9.93 & 0.025 & 127 \\ \hline TiO\({}_{2}\)—Rutile & 4.38 & 0.009 & 100 \\ \hline
0.1 Cu/TiO\({}_{2}\) (R) & 3.91 & 0.010 & 110 \\ \hline
0.25 Cu/TiO\({}_{2}\) (R) & 3.91 & 0.010 & 109 \\ \hline
0.5 Cu/TiO\({}_{2}\) (R) & 3.89 & 0.010 & 131 \\ \hline
0.25 Cu/TiO\({}_{2}\) (A) & 9.40 & 0.027 & 142 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Pore analysis characteristics.  
Figure 5: (a) Type II isotherm according to IUPAC (prepared according to [39]). And (b) Isotherm curve of sample 0.5 Cu/TiO\({}_{2}\) (R).