Photocatalytic Hydrogen Evolution from Water Using Copper Gallium Sulfide under Visible-Light Irradiation

Abstract

Copper gallium sulfide with a chalcopyrite-type structure (CuGa 3 S 5 ) and a band gap of ca. 2.4 eV was prepared by a solid-state reaction. The as-prepared CuGa 3 S 5 exhibited photocatalytic hydrogen evolution activity in an aqueous solution containing Na 2 S and Na 2 SO 3 as sacrificial electron donors under visible-light irradiation (λ > 420 nm), even without a cocatalyst, such as platinum (Pt). The photocatalytic activity, however, was improved by the deposition of noble metal cocatalysts. Among the noble metals tested, rhodium (Rh) was found to be the most effective cocatalyst to improve the H 2 evolution activity, which was 2.5 times that achieved without a cocatalyst. Dispersion of base sulfides, including nickel sulfide (NiS) and iron sulfide (FeS), into the reactant solution containing CuGa 3 S 5 also increased the activity. The activity under optimized conditions (5.0 wt % NiS/CuGa 3 S 5 ) was 3 times that of a similarly optimized Rh/CuGa 3 S 5 . The results of electrochemical measurements and photocatalytic reactions suggested that NiS suspended in the reactant solution accepts electrons from the excited state of CuGa 3 S 5 to reduce H + into H 2 when NiS and CuGa 3 S 5 particles collide with each other in the reactant solution.

Solvent-induced deposition of Cu–Ga–In–S nanocrystals onto a titanium dioxide surface for visible-light-driven photocatalytic hydrogen production

“…The Ru sulfide species was deposited on the CGIS outer surface and acted as a co-catalyst, consistent with the recent literature [21], although we failed to identify Ru species in TEM images probably due to their low contrast between Ru and CGIS material. Figure 3 and 4 here performed in the range where the photocatalytic H2 evolution rate increases with an increasing amount of photocatalyst, i.e., before saturation.…”

Nickel-based cocatalysts for photocatalytic hydrogen production

“…Ni-based sulfides, such as NiS and NiS 2 , also serve as efficient cocatalysts for photocatalytic H 2 production by coupling with proper photocatalysts [50][51][52][53][54][55][56][57][58][59][60][61]. As a p-type semiconductor, NiS has been applied in a wide range of areas due to its unique properties.…”

“…In particular, Ni-based materials demonstrate excellent activity and have received much attention as H 2 -evolution cocatalysts. Many kinds of Ni-based cocatalysts, such as metallic Ni [38][39][40][41][42][43][44][45][46][47][48][49], sulfides [50][51][52][53][54][55][56][57][58][59][60][61], phosphides [62], oxides [63][64][65][66][67][68][69], hydroxides [70][71][72][73][74][75][76][77], hydrogenases [78][79][80][81], as well as molecular complexes [81][82][83][84][85][86]…”

Electronic structure and photocatalytic activity of wurtzite Cu–Ga–S nanocrystals and their Zn substitution

“…Cu−Ga−S ternary compounds can absorb light up to 550 nm, which makes them good candidates as visible-light responsive photocatalysts. 4 To enhance the H 2 production rate and reduce the photocorrosion commonly observed for sulfur containing photocatalysts, a S 2− /SO 3 2− solution has been employed. 5,6 S 2− reagents irreversibly react with the photogenerated holes to produce polysulfides typically, and the photogenerated electrons promote the H 2 evolution reaction.…”