Core/Shell Structured La- and Rh-Codoped SrTiO₃ as a Hydrogen Evolution Photocatalyst in Z-Scheme Overall Water Splitting under Visible Light Irradiation

Abstract

The effects of preparation methods, calcination times, and La doping concentrations on the crystallinity, visible light absorption, and photocatalytic water splitting performance of Rh- and La-codoped SrTiO3 (SrTiO3:La/Rh) were investigated. Applying a two-step solid state reaction in which SrTiO3 acted as a perovskite-type host produced core/shell structured SrTiO3:La/Rh, the surface of which was enriched with the dopants. La doping suppressed the formation of oxygen vacancies and inactive Rh4+ species. Under visible light irradiation (λ > 420 nm), SrTiO3:La/Rh exhibited 3.5 and 3.8 times higher rates of H2 evolution in an aqueous methanol solution and during redox-free Z-scheme overall water splitting in combination with Ir/CoO x /Ta3N5, respectively, compared to SrTiO3:Rh. The solar-to-hydrogen efficiency of the Z-scheme system as measured under illumination with simulated sunlight (AM1.5G) was found to have improved by a factor of 3.

All-in-one synthesis of mesoporous silicon nanosheets from natural clay and their applicability to hydrogen evolution

“…Furthermore, because of the abundance of the raw materials, the low fabrication cost and excellent hydrogen production performance, SiNSs have great potential for use as a photocathode material that compares favorably with other top-down-processed Si materials for PEC water-splitting systems. 7,40 …”

Evaluating particle-suspension reactor designs for Z-scheme solar water splittingviatransport and kinetic modeling

“…For Option I, the OER material was TiO 2 ( E bg = 3.1 eV [59], average value of its two most common crystal structures) and for Option II the OER material was BiVO 4 ( E bg = 2.5 eV) [20,60], both materials with high reported activities for the light-driven OER in Z-scheme designs [41,49,50,61]. The HER material for both these options was rhodium-doped SrTiO 3 , with a lowest-energy absorption onset of 2.5 eV, due to [74,75] excitation from a Rh 3+ defect band to the SrTiO 3 conduction band [62], and one-of-thebest reported activities for the light-driven HER in Z-scheme designs [45,48,51]. Table 1 shows the band gaps of the selected photocatalysts, which have suitable band-edge positions for the valence and conduction bands (denoted by E vb and E cb in Table 2) relative to the desired redox reaction potentials.…”

“…The predominant focus in the aforementioned studies was the identification of semiconductor materials [40][41][42][43][44][45][46][47][48] with enhanced activities for implementing the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), development of surface treatment techniques and selection of redox shuttles to suppress undesired interfacial electron-transfer reactions [41,49], and evaluation of the effectiveness of cocatalyst [50] and coating materials [51]. In prior work, device-scale design and performance dependences on the transport and kinetic processes of the system were not considered.…”

Hydrogen Generation through Solar Photocatalytic Processes: A Review of the Configuration and the Properties of Effective Metal-Based Semiconductor Nanomaterials

“…Nevertheless, "metal-semiconductor" heterojunctions mostly provide photoactivation under light irradiation with wavelengths shorter than 400 nm. Amongst recently-developed "metal-semiconductor" heterojunctions with a narrow band gap and band edges suitable for water photosplitting, Pt/PbBi 2 Nb 2 O 9 [42], (V,Rh)/SrTiO 3 [43], (Zn,Rh,Cr)/Ga 2 O 3 [41], (La,Rh,Au)/SrTiO 3 [44], Au/CeO 2 [45], (Mo,Au)/BiVO 4 [46], sulfide-based materials [22], CoO [47] and cadmium chalcogenides [48] have to be noted.…”