Gd-doped BiVO4 microstructure and its composite with a flat carbonaceous matrix to boost photocatalytic performance

Fabrication of semiconductor-based photocatalysts with excellent charge separation efficiency has gained substantial attention due to their notable performance for water treatment applications. Herein, we synthesized a flat reduced graphene oxide-based gadolinium-doped bismuth vanadate (rGO/Gd/BiVO4) composite by a facile hydrothermal and ultra-sonication approach. By examining the photodegradation of Methylene Blue (MB) dye from an aqueous solution under visible light, we compared the photocatalytic behavior of the rGO/Gd/BiVO4 composite to that of pristine BiVO4 and Gd/BiVO4. The photo-excited electron/hole pair recombination was suppressed by adding Gd and rGO to BiVO4. This led to rGO/Gd/BiVO4 having a faster rate (k = 0.027 min−1) of MB degradation than Gd/BiVO4 (k = 0.0095 min−1) and pure BiVO4 (k = 0.006 min−1). In particular, the rGO/Gd/BiVO4 degraded almost 97% of the MB dye under visible-light irradiation in 100 min, whereas the BiVO4 and Gd/BiVO4 samples removed only 53% and 69% of the MB dye, respectively. The rGO/Gd/BiVO4 composite displayed 16-fold and 2.40-fold larger transient photocurrent responsiveness than the BiVO4 and Gd/BiVO4 samples. Subsequently, the BiVO4 and Gd/BiVO4 showed a charge recombination rate of 2.18 and 3.62 s, separately, which was relatively smaller than the rGO/Gd/BiVO4 result (= 8.41 s). The increased photocatalytic activity of rGO/Gd/BiVO4 is due to the development of heterojunction between Gd/BiVO4 and the rGO sheets, which facilitates the absorption of photons as well as the separation of photogenerated electrons and holes.