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Transient Behavior of Ni@NiO x Functionalized SrTiO 3 in Overall Water Splitting

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ABSTRACT

Transients in thecomposition of Ni@NiOx core–shellco-catalysts deposited on SrTiO3 arediscussed on the basis of state-of-the-art continuous analysis ofphotocatalytic water splitting, and post-XPS and TEM analyses. Theformation of excessive hydrogen (H2:O2 ≫2) in the initial stages of illumination demonstrates oxidation ofNi(OH)2 to NiOOH (nickel oxyhydroxide), with the lattercatalyzing water oxidation. A disproportionation reaction of Ni andNiOOH, yielding Ni(OH)2 with residual embedded Ni, occurswhen illumination is discontinued, which explains repetitive transientsin (excess) hydrogen and oxygen formation when illumination is reinitiated.

No MeSH data available.


Transient behavior in H2 and O2 evolutionduring photocatalytic water splitting of 25 mg of BSTO-1000-NiOx (black trace, hydrogen; red trace, oxygen).
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fig2: Transient behavior in H2 and O2 evolutionduring photocatalytic water splitting of 25 mg of BSTO-1000-NiOx (black trace, hydrogen; red trace, oxygen).

Mentions: To obtainfurther insights into the transient behavior in the initialphase of photocatalytic water splitting, variable times between illuminationand dark conditions were applied. The obtained results are shown in Figure 2. The initial transientsare in good agreement with the results presented in Figure 1. After purging of the reactorwith pure helium for 1 h in dark conditions, a new maximum (72% ofthe initial maximum) in activity of H2 evolution was obtained,when illumination was reinitiated. Consecutive dark–light cyclesshow that the initial H2 evolution rate is dependent onthe duration of the dark treatment. After treatment in dark conditionsfor 48 h, the initial H2 evolution rate can be fully recovered,although the duration of the transient appears shorter than for thefresh catalyst. The consecutive transient again shows that ∼73%of the initial hydrogen activity can be recovered after 1 h in darkconditions. The oxygen evolution rate is significantly larger afterkeeping the reactor for 48 h in darkness (without reaching a maximum)than that obtained for the fresh catalyst, and at the end of the finaltransient, the catalyst is providing a H2:O2 ratio close to 2:1.


Transient Behavior of Ni@NiO x Functionalized SrTiO 3 in Overall Water Splitting
Transient behavior in H2 and O2 evolutionduring photocatalytic water splitting of 25 mg of BSTO-1000-NiOx (black trace, hydrogen; red trace, oxygen).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384480&req=5

fig2: Transient behavior in H2 and O2 evolutionduring photocatalytic water splitting of 25 mg of BSTO-1000-NiOx (black trace, hydrogen; red trace, oxygen).
Mentions: To obtainfurther insights into the transient behavior in the initialphase of photocatalytic water splitting, variable times between illuminationand dark conditions were applied. The obtained results are shown in Figure 2. The initial transientsare in good agreement with the results presented in Figure 1. After purging of the reactorwith pure helium for 1 h in dark conditions, a new maximum (72% ofthe initial maximum) in activity of H2 evolution was obtained,when illumination was reinitiated. Consecutive dark–light cyclesshow that the initial H2 evolution rate is dependent onthe duration of the dark treatment. After treatment in dark conditionsfor 48 h, the initial H2 evolution rate can be fully recovered,although the duration of the transient appears shorter than for thefresh catalyst. The consecutive transient again shows that ∼73%of the initial hydrogen activity can be recovered after 1 h in darkconditions. The oxygen evolution rate is significantly larger afterkeeping the reactor for 48 h in darkness (without reaching a maximum)than that obtained for the fresh catalyst, and at the end of the finaltransient, the catalyst is providing a H2:O2 ratio close to 2:1.

View Article: PubMed Central - PubMed

ABSTRACT

Transients in thecomposition of Ni@NiOx core–shellco-catalysts deposited on SrTiO3 arediscussed on the basis of state-of-the-art continuous analysis ofphotocatalytic water splitting, and post-XPS and TEM analyses. Theformation of excessive hydrogen (H2:O2 ≫2) in the initial stages of illumination demonstrates oxidation ofNi(OH)2 to NiOOH (nickel oxyhydroxide), with the lattercatalyzing water oxidation. A disproportionation reaction of Ni andNiOOH, yielding Ni(OH)2 with residual embedded Ni, occurswhen illumination is discontinued, which explains repetitive transientsin (excess) hydrogen and oxygen formation when illumination is reinitiated.

No MeSH data available.