Solar Water Splitting Utilizing a SiC Photocathode, a BiVO₄ Photoanode, and a Perovskite Solar Cell

Abstract

We have successfully demonstrated solar water splitting using an ewly fabricated photoelectrochemical system with aP tloaded SiC photocathode, aC oO x -loaded BiVO 4 photoanode, and ap erovskite solar cell. Detection of the evolvedH 2 and O 2 with a1 00 %F aradaic efficiencyi ndicates that the observed photocurrent was used for water splitting.T he solar-to-hydrogen (STH) efficiency was 0.55 %under no additional bias conditions.Photoelectrochemical water splitting is an attractive reaction to convert solar energy to chemical energy,t he so-called artificial photosynthesis. In ap hotoelectrode system, electric bias can be applied between ap hotoanode and ap hotocathode. Moreover,H 2 is obtained separately from O 2 in the photoelectrode system.T here are many visible-light-driven photocathodes such as Cu I -containing metal sulfides [1][2][3][4][5][6] and selenides, [7,8] Rh-doped SrTiO 3 , [9] CaFe 2 O 4 , [10] and SiC; [11][12][13] and photoanodes such as WO 3 , [14][15][16] BiVO 4 , [17][18][19][20][21][22][23][24] Fe 2 O 3 , [25][26][27] SnNb 2 O 6 , [28] TaON, [29] Ta 3 N 5 , [30][31][32][33] LaTiO 2 N, [34,35] BaTaO 2 N, [36,37] and SrNbO 2 N. [38,39] Herein, we focusedo nS iC as ap hotocathode and BiVO 4 as a photoanode. To construct ap hotoelectrode system;t he photocurrentd ensity,onset potential of the photocurrent, and stability are importantf actors. Cu I -containing metal sulfides and selenides give excellent cathodic photocurrents, although their onset potentials are not very positive. [1][2][3][4][5][6][7][8] Moreover,t he chemical instability in water of metal sulfides and selenides still remains an issue. [2,6,7] Chemically stable metal oxides of RhdopedS rTiO 3 and CaFe 2 O 4 possess largely positive onset potentials,w hereas the photocurrents are low. [9,10] From this point of view,t he SiC with relativelyp ositive onset potential (1.15 Vvs. RHE), high photocurrent, and high stability is asuitable candidate as ap hotocathode in the photoelectrochemical water splitting system.[13] Regardingt he photoanode candidate, BiVO 4 shows the most negative onset potential and high photocurrent under simulated sunlight irradiation.To achieve high solar energy conversion efficiency,t he use of aw ider ange of sunlight, especially visible light, is important. Aw eak point of the SiC and BiVO 4 is the relativelyw ide band gap of 2.4-2.5 eV (about 500 nm) as visible-light-responsive materials. Because transparent SiC and BiVO 4 photoelectrodes can be prepared, [12,20] we focus on their combination with ap erovskite solarc ell to overcome this issue. [40,41] In more detail, the perovskite solar cell can absorb transmitted light through the transparent SiC and/or BiVO 4 photoelectrodes, because it can utilize visible light up to about 800 nm. Moreover, the photovoltage of about 1.1 Vc an be used for the photoelectrochemical system to assist water splitting. Actually,t here are some reports about the combined system of ap erovskite solar cell with aB iVO 4 photoelectrode for water oxidation to

Multilayered Hematite Nanowires with Thin‐Film Silicon Photovoltaics in an All‐Earth‐Abundant Hybrid Tandem Device for Solar Water Splitting

“…After 28 h continuous PEC‐WS operation, the hybrid tandem device showed good robustness, and 94 % of the initial bias‐free photocurrent density was retained (4.3 mA cm −2 ). Referring to the state‐of‐the‐art oxide‐based PEC‐WS devices in the literature, this is an outstanding bias‐free photocurrent density, outperforming similar tandem device approaches, which usually operate at current densities below 1 mA cm −2 (for 1 sun illumination intensity) and use noble‐metal catalysts . Table S2 (Supporting Information) summarizes recent studies on hybrid tandem devices for unassisted water splitting.…”

“…Referring to the state-of-the-arto xide-based PEC-WS devices in the literature, this is an outstanding bias-free photocurrent density, outperforming similar tandem device approaches, which usually operate at current densities below 1mAcm À2 (for 1sun illuminationi ntensity) and use noble-metal catalysts. [7][8][9][22][23][24][25][26][27][28][29] Ta ble S2 (Supporting Information) summarizesr ecent studies on hybrid tandem devices for unassisted water splitting. A long-term stabilityt est confirmed that the Ni foil/Nif oam catalyst structure, as well as the hematite nanowires tructures, ensured excellent protectiono ft he photocathode andp hotoanode in harsh basic solutions (1 m NaOH), respectively.…”

Metal halide perovskite: a game-changer for photovoltaics and solar devices via a tandem design

“…Analogous to the multi-junction tandem solar cell, perovskite can behave as an ideal wide bandgap top absorber in PV/PEC tandem device. So far, perovskite PVs have been paired with some of the widely studied photoelectrodes made of materials like hematite [167], BiVO 4 [169][170][171][172][173], and Cu 2 O [174] for solar water splitting in PV/PEC configuration. The highest unbiased photocurrent density of ~5.7 mA/cm 2 corresponding to STH efficiency of 6.3% has been realized when used in tandem with BiVO 4 photoanode [169,170].…”

Spin‐Coated Bismuth Vanadate Thin Film as an Alternative Electron Transport Layer for Light‐Emitting Diode Application

“…[15] Ternary metal oxide systems such as Zn 2 SnO 4 , Mn 2 SnO 4 , BaSnO 3 , and BiVO 4 possess excellent electrical transport properties compared with binary oxide systems. [16][17][18][19] The ternary metal oxides possess higher carrier concentration and higher mobility, which can promote the charge transfer process more effectively. Recently, ternary bismuth vanadate (BVO) material has been explored for potential applications due to its easily tunable electrical and optical properties.…”

“…[24] Many articles are available in the literature which describes for the BiVO 4 on dye degradation and water splitting applications. [18,19] BiVO 4 is widespread for water splitting and photocatalysis applications because of its low bandgap and the possibility to promote electron injection into other semiconductors. [25][26][27] To the best of our knowledge, investigation of the BiVO4 thin film layer as an ETL has not been performed so far.…”