La₅Ti₂Cu_1−xAg_xS₅O₇photocathodes operating at positive potentials during photoelectrochemical hydrogen evolution under irradiation of up to 710 nm

Abstract

Photoelectrodes of Al-doped La5Ti2Cu1−xAgxS5O7powder generate a photocathodic current attributable to the hydrogen evolution reaction at +0.7 Vvs.RHE.

Sunlight‐Driven Overall Water Splitting by the Combination of Surface‐Modified La5Ti2Cu0.9Ag0.1S5O7 and BaTaO2N Photoelectrodes

“…Figure presents the quantities of evolved gases obtained using this PEC cell without applying an external bias voltage under irradiation by a 300 W Xe lamp equipped with filters. The H 2 and O 2 generation rates were approximately three times higher than those previously reported for a PEC cell composed of a Pt/Al‐LTCA photocathode and a Co/BTON photoanode in an aqueous sulfate solution . Moreover, the PEC cell composed of the Pt/TiO 2 /CBT/Al‐LTCA and the Ir/Co/BTON photoelectrodes could generate an order of magnitude greater gas evolution rate compared to the PEC cell composed of the Pt/Al‐LTCA and the Co/BTON photoelectrodes in strongly alkaline aqueous phosphate solution (see Figure S11).…”

“…Photoelectrochemical (PEC) water splitting is a promising means of obtaining renewable hydrogen directly from water, utilizing sunlight. A typical PEC cell for two‐step water splitting is composed of a photocathode and a photoanode which are connected to one another . This combination of photoelectrodes can relax the strict requirements for each individual photoelectrode, such as the conduction band minimum and valence band maximum, through the additive effect of the two driving forces.…”

“…The photocurrent and working potential ( E work ) for a PEC cell are determined by the intersection of the current–potential ( i – E ) curves for the photocathode and photoanode that are used . A solar‐to‐hydrogen energy conversion efficiency (STH) of at least 10 % is required to be cost‐competitive with a steam‐reforming process . However, it is still a challenging task to achieve this sufficient level of STH.…”

“…Our group recently reported that a PEC cell composed of Al‐doped La 5 Ti 2 Cu 0.9 Ag 0.1 S 5 O 7 (Al‐LTCA) and BaTaO 2 N (BTON) photoelectrodes fabricated through particle‐transfer (PT) methods is capable of spontaneous overall water splitting under visible light with a high Faradaic efficiency . Al‐LTCA and BTON are photocatalytic materials with absorption edges at λ =710 and 660 nm, respectively .…”

“…One of the main reasons for this low photocurrent is believed to have been the use of a non‐optimal electrolyte, since the pH 11 aqueous sulfate solution employed in the PEC cell is not preferable for both the photoelectrodes . It is important to note that an Al‐LTCA photocathode can show a relatively high photocurrent in a weakly alkaline aqueous sulfate solution, but the photocurrent will decrease significantly in strongly alkaline aqueous phosphate solutions . In contrast, a BTON photoanode can exhibit a relatively large photocurrent in a strongly alkaline aqueous phosphate solution …”