Dye-sensitized photoelectrochemical water oxidation through a buried junction

Abstract

Water oxidation has long been a challenge in artificial photosynthetic devices that convert solar energy into fuels. Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) provide a modular approach for integrating light-harvesting molecules with water-oxidation catalysts on metal-oxide electrodes. Despite recent progress in improving the efficiency of these devices by introducing good molecular water-oxidation catalysts, WS-DSPECs have poor stability, owing to the oxidation of molecular components at very positive electrode potentials. Here we demonstrate that a solid-state dye-sensitized solar cell (ss-DSSC) can be used as a buried junction for stable photoelectrochemical water splitting. A thin protecting layer of TiO grown by atomic layer deposition (ALD) stabilizes the operation of the photoanode in aqueous solution, although as a solar cell there is a performance loss due to increased series resistance after the coating. With an electrodeposited iridium oxide layer, a photocurrent density of 1.43 mA cm was observed in 0.1 M pH 6.7 phosphate solution at 1.23 V versus reversible hydrogen electrode, with good stability over 1 h. We measured an incident photon-to-current efficiency of 22% at 540 nm and a Faradaic efficiency of 43% for oxygen evolution. While the potential profile of the catalyst layer suggested otherwise, we confirmed the formation of a buried junction in the as-prepared photoelectrode. The buried junction design of ss-DSSs adds to our understanding of semiconductor-electrocatalyst junction behaviors in the presence of a poor semiconducting material.

Janus‐Structured Co‐Ti3C2 MXene Quantum Dots as a Schottky Catalyst for High‐Performance Photoelectrochemical Water Oxidation

“…To the best of our knowledge, the PEC water oxidation and stability of as constructed Co‐MQD photoelectrocatalyst are comparable or even superior to the works on other classical high performance photoanode materials, such as TiO 2 , [ 44,45 ] BiVO 4 , [ 46 ] Fe 2 O 3 , [ 47–52 ] ZnO, [ 53 ] and MoS 2 . [ 54 ] As shown in Table S5, Supporting Information, at a bias potential of 1.23 V versus RHE, the Co‐MQD‐48 photoanode achieves almost the highest current density of 2.99 mA cm −2 , making it among the state‐of‐the‐art performance in PEC water oxidation.…”

Excitation energy-dependent photocurrent switching in a single-molecule photodiode

“…S20. The 1 H NMR, 13 C NMR, and electrospray ionization mass spectrometry (ESI-MS) are given in SI Appendix, Figs. S1-S3.…”

“…The final product (47 mg; 25% yield based on ZnRuCl 3 ) was obtained following removal of acetone under reduced pressure. The 1 H NMR, 13 C NMR, and ESI-MS are given in SI Appendix, Figs. S4-S6.…”

“…With those devices, electrical and electronic processes can be modified by varying functional electrode elements and integrating individual molecular components that respond to external stimuli, such as electrochemical redox potentials, optical excitation, and magnetic fields (3)(4)(5)(6)(7). Photoresponsive molecular diodes have been used in dye-sensitized photoelectrodes to generate electron-hole pairs for catalytic and optoelectronic applications (8)(9)(10)(11)(12)(13)(14). They convert solar energy into electrical signals and chemical energy by transfer of photogenerated electrons following optical excitation.…”

A conductive metal–organic framework photoanode

“…[1][2][3][4][5][6][7][8] Interfacial charge transfer at the electrode surface allows separation of the photogenerated electron-hole pair, transferring the electron (or, the hole) across the interface. [9][10][11][12][13][14][15][16] The chargeseparation process has been extensively studied in photoanodes of dye-sensitized photoelectrochemical cells [17][18][19][20] where photoexcited molecular dyes inject electrons into the conduction band of a metal oxide, leaving electron-holes on the dyes anchored to the electrode surface. The holes are then transferred to an oxidation catalyst to perform, for example, water oxidation.…”