###### Abstract
It is challenging to meet all of the needs, using only a semiconductor, for photocatalysis, such as having a wide visible-light response, long-term stability and a strong redox capacity, as well as preventing fast electron-hole recombination. A beneficial means that can be applied to enhance the properties of semiconductors is the type-II heterojunction, shown in Figure 1[20]. The latter is formed when two semiconductors capable of absorbing light with different energy bands are put in contact. In this arrangement, the valence band (VB) of photocatalyst-I (PC-I) is more positive than the VB of PC-II, while the conduction band (CB) of PC-II is more negative compared to the CB of PC-I, as reported in Figure 1. When light irradiates the semiconductor surfaces, each generates an excited electron that transitions from the VB to the CB. In type-II heterojunctions, photo-promoted electrons tend to accumulate in the material with a more positive CB potential. On the other hand, holes tend to accumulate in the semiconductor with a more negative VB [21]. This kind of heterojunction differs from the so-called Z-scheme ones, where after two excited electrons and holes are generated, the electrons from the lower conduction band can recombine with the holes in the highest energy band, following the Z-scheme and making the potential differences between the holes and electrons higher than each of the materials alone [20; 22]. Flame spray pyrolysis (FSP) is a promising route, but other well-established techniques have been widely explored in the literature to synthetize type-II heterojunctions with tunable properties as well. For the sake of completeness, some papers on different techniques that appeared of interest to the authors are given below. [PERSON] et al. reported the synthesis of Zn\({}_{x}\)In\({}_{y}\)S\({}_{z}\) by the hydrothermal method, and the relative Zn\({}_{x}\)In\({}_{y}\)S\({}_{z}\)/ZnO composites with internal type-II heterojunctions prepared by a solvent-assisted interface,highlighting how the latter significantly enhanced the separation of the photocarriers [23]. Lately, electrospinning has gained attention as a method for fabricating one-dimensional (1D) nanostructured photocatalysts. This technique allows for the formation of nanofibers with high ratios, as well with large surface areas, for catalytic reactions. Experiments performed on TiO\({}_{2}\)/CdS nanofiber heterojunctions have reported significant improvements as H\({}_{2}\) production photocatalysts, due to the formation of type-II heterojunctions that facilitate charge separation [24]. Despite the higher redox potential of the Z-scheme, type-II heterojunctions are able to improve photocatalytic efficiency when two materials are placed in intimate contact. It is well known that TiO\({}_{2}\)'s performance as a photocatalyst is highly affected by its extremely short e lifetime [25]. In this sense, the WO\({}_{3}\)/TiO\({}_{2}\) type-II heterojunction can play a crucial role in enhancing charge separation and supporting CO\({}_{2}\) reduction. [PERSON] et al. investigated WO\({}_{3}\)/TiO\({}_{2}\) heterostructures towards organic contaminant degradation, reporting a particular improvement in the catalytic activity of the material for the 40 wt% WO\({}_{3}\)/TiO\({}_{2}\) sample due to the larger interface and contact between the two phases [26]. In this study, we present a novel TiO\({}_{2}\)/WO\({}_{3}\) hybrid material, synthetized though the flame spray pyrolysis (FSP) technique, that has been characterized in-depth and tested for CO\({}_{2}\) photoreduction in a high-pressure photoreactor. The FSP technique allows us to place different materials in intimate contact as a strategy to favor the electron-hole transfer, improving the performances of the single photocatalysts.