Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1%

Abstract

Photocatalytic water splitting using particulate semiconductors is a potentially scalable and economically feasible technology for converting solar energy into hydrogen. Z-scheme systems based on two-step photoexcitation of a hydrogen evolution photocatalyst (HEP) and an oxygen evolution photocatalyst (OEP) are suited to harvesting of sunlight because semiconductors with either water reduction or oxidation activity can be applied to the water splitting reaction. However, it is challenging to achieve efficient transfer of electrons between HEP and OEP particles. Here, we present photocatalyst sheets based on La- and Rh-codoped SrTiO3 (SrTiO3:La, Rh; ref. ) and Mo-doped BiVO4 (BiVO4:Mo) powders embedded into a gold (Au) layer. Enhancement of the electron relay by annealing and suppression of undesirable reactions through surface modification allow pure water (pH 6.8) splitting with a solar-to-hydrogen energy conversion efficiency of 1.1% and an apparent quantum yield of over 30% at 419 nm. The photocatalyst sheet design enables efficient and scalable water splitting using particulate semiconductors.

Engineering oxygen vacancy on rutile TiO2 for efficient electron-hole separation and high solar-driven photocatalytic hydrogen evolution

“…In a typical, 4 g of commercial rutile TiO 2 (denoted as i, 98.8%, CAS: 13463-67-7) was mixed with 1.5 g of NaBH 4 (98%, CAS: 16940-66-2, Aladdin Reagent Company). After thoroughly ground for 30 min, the mixture was heated from room temperature (RT) to 250, 300, and 350°C (denoted as ii, iii and iv) for 1 h under nitrogen atmosphere with a heating rate of 5°C min −1 , respectively.…”

“…After thoroughly ground for 30 min, the mixture was heated from room temperature (RT) to 250, 300, and 350°C (denoted as ii, iii and iv) for 1 h under nitrogen atmosphere with a heating rate of 5°C min −1 , respectively. After naturally cooling to RT, the obtained product was dispersed into water with vigorous stirring for 30 min and then aged for 24 h. The powder was washed with ethanol and deionized water for several times to remove unreacted NaBH 4 , and dried at 60°C overnight, and finally the rutile TiO 2 with different contents of oxygen vacancy were obtained. Deionized water was used for all experiments.…”

“…Hence, photocatalytic hydrogen production attracts much more attention recently [2][3][4]. Since Fujishima and Honda [5][6][7] discovered hydrogen production from water splitting on TiO 2 for the first time, it is considered as the most promising photocatalyst candidate due to nontoxicity, high stability and low-cost [8][9][10].…”

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.…”

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

“…Recent technoeconomic analyses [35][36][37] make evident the need for fixed-electrode PEC devices to be operated at STH efficiencies greater than 25% to reach price parity with hydrogen produced from fossil fuels. However, the electrode-based devices that were stable for at least one day have exhibited STH efficiencies of at best 2% and they utilized designs that were inherently unsafe due to the generation of an explosive mixture of the H 2 and O 2 reaction products [20,38,39].…”