Promoting the formation of Co (III) electrocatalyst with diamond anodes

Escalona-Durán, Florymar; Muñoz-Morales, M.; Souza, F.L.; Sáez, Cristina; Cañizares, Pablo; Martínez‐Huitle, Carlos A.; Rodrigo, Manuel A.

doi:10.1016/j.jelechem.2021.115007

Cited by 7 publications

(2 citation statements)

References 19 publications

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“…3d). Moreover, it has been reported that Co 3+ is highly unstable in water and is converted into Co 2+ species [38,39]. Therefore, we propose that the photogenerated holes may oxidize Co 2+ at the electrode interface to Co 3+ , which oxidizes water to O 2 while reducing to Co 2+ in the bulk electrolyte.…”

Section: Co 2+ Ions As a Homogeneous Oer Catalystmentioning

confidence: 85%

Improving WO3/SnO2 photoanode stability by inhibiting hydroxyl radicals with cobalt ions in strong acid

Shi

Cui

2022

Sci. China Mater.

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Photoelectrochemical (PEC) water splitting in acid is promising, but its development has been hindered by the lack of stable photoanodes and effective nonprecious cocatalysts. WO 3 is one of the few acid-stable semiconductors, but its fast performance decay under illumination remains elusive and unsolved. Herein, we present that the fast photocurrent decreases of both WO 3 and WO 3 /SnO 2 photoanodes were caused by the hydroxyl radicals (OH•) generated at the electrode/electrolyte interfaces, and we solved this issue by introducing cobalt (Co 2+ ) ions into the electrolyte at pH 0.3, allowing for the efficient oxidation of H 2 O to O 2 rather than to detrimental OH• radicals, with the Faradaic efficiency toward oxygen evolution increasing from 40% to 95% and the photocurrent density increasing from 0.6 to 0.8 mA cm −2 and being stable for 25 h at 1.2 V (reversible hydrogen electrode). Importantly, the scavenging of OH• radicals by vitamin C demonstrated the same photocurrent stability as the introduction of Co 2+ ions, further implying the crucial inhibiting role of Co 2+ ions. In-situ ultraviolet-visible and Raman spectroscopy indicated the trapping of surface holes by the oxidation of Co 2+ to Co 3+ , and electron paramagnetic resonance revealed the role of Co 2+ ions in the inhibition of OH• radicals. This study provides an ideal model for combining a homogeneous redox-active Co 2+ /Co 3+ couple with a photoanode for water oxidation in strong acid.

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Section: Co 2+ Ions As a Homogeneous Oer Catalystmentioning

confidence: 85%

Improving WO3/SnO2 photoanode stability by inhibiting hydroxyl radicals with cobalt ions in strong acid

Shi

Cui

2022

Sci. China Mater.

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“…In literature [30][31][32], it is reported a very positive effect in the efficiency of the electroscrubbers by adding into the absorbent/electrolyte Co(II) salts, because they become precursors or electrochemical mediators of Co(III) [33]. As the generation of this mediator was previously confirmed [39], to verify this potential improvement in novel systems developed, Figure 4 focused on the effect of the addition of cobalt mediators with both electro-scrubbers. As observed, and opposite to what initially expected, the effect is not positive, but negative in the case of the jet-mixer and almost neutral in the case of the packed column electro-scrubber.…”

Section: Resultsmentioning

confidence: 89%