NaBH4 raises Ni3+ and speeds NiFe LDH OER

Treating NiFe layered double hydroxide with NaBH4 lifts Ni3+/Ni2+ from 0.39 to 1.32 and gives 95.9% faradaic efficiency for O2.

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What does NaBH4 do to NiFe LDH?

It enriches Ni3+, which is crucial for OER catalysis.

How did Ni3+/Ni2+ and Fe2+/Fe3+ change?

Ni3+/Ni2+ 0.39 → 1.32; Fe2+/Fe3+ 0.40 → 1.49.

What O2 faradaic efficiency was calculated?

95.9%.

How much O2 was collected in the FE experiment?

7.48 × 10−5 mol at 50 mA for 10 min.

What atomic picture do the authors give?

Hydride deprotonates Ni–OH and makes an oxygen vacancy near Fe, yielding Ni3+ and Fe2+.

Why is Ni3+ thought to help OER?

Lower coordination and stronger H2O adsorption promote OOH deprotonation to O2.

What EXAFS change marks Fe-site vacancies?

Fe–O coordination falls from 6.0 to 5.6 with a larger Debye–Waller factor.

Does Ni–O coordination change as much?

Barely: N ≈ 6.0 to 5.9.

Is the strategy only for NiFe LDH?

Authors say it generalizes to other transition-metal LDHs.

What XPS Ni 2p fits were used?

Ni3+ at 856.2 eV and Ni2+ at 855.1 eV.

Why is OER the bottleneck of water splitting?

Its four-electron transfer imposes a high overpotential.