NOVELTY - A system (S1) of photoanodes in tandem comprises photoanode based on titanium dioxide (TiO2) and cadmium compound selected from cadmium sulfide (CdS) and cadmium selenide (CdSe), and photoanode based on titanium dioxide and bismuth sulfide (Bi2S3).    USE - As system of photoanodes in tandem (claimed).    ADVANTAGE - The system allows the handling with low environmental impact, of gaseous streams having low content of H2S of wide range of productive origins; allows production of high-purity H2; allows the production of S which can be used in the production of chemicals, which can be recovered according to various methods; does not require costly investments; does not require high temperatures, it is possible to operate at room temperature; does not produce CO2; does not require separation or purification steps; does not use adsorbing materials with regeneration passages; uses direct solar light, it does not require UV irradiation sources, as described in other methods of the prior art; does not produce waste-products to be managed; does not require the use of additional oxidizing gases; is not only possible to avoid the use of toxic gas H2S, but also to treat higher concentrations in solution, rather than operating directly with H2S.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) photoelectrolytic cell comprising the system (S1);    (2) process (P1) for the photoproduction of H2 from aqueous solutions containing sulfides, effected using the system (S1);    (3) photoanode (A1) based on TiO2 and Bi2S3, where the Bi2S3 possibly being in a continuous or discontinuous thin layer; and    (4) preparing photoanodes based on TiO2 and cadmium compound selected from CdS and CdSe, involving mixing CdS powder with an aqueous gel of nanocrystalline TiO2 in the presence of an organic binder, obtaining a suspension, distribution of the suspension on conductor substrate by means of the blade casting technique, drying and sintering at 400-550 degrees C for 30-60 minutes.