Electrochemistry
NaBH4 raises Ni3+ and speeds NiFe LDH OER
Open access · cc by · source: Europe PMC
Treating NiFe layered double hydroxide with NaBH4 lifts Ni3+/Ni2+ from 0.39 to 1.32 and gives 95.9% faradaic efficiency for O2.
Study at a glance
- Design
- Other — NaBH4 reduction of NiFe LDH to raise Ni3+/Ni2+ and oxygen vacancies for OER
- N
- Electrocatalysis materials study — no sample N
- Population
- NiFe layered double hydroxide electrocatalysts
- Outcome
- OER activity and O2 faradaic efficiency after hydride treatment
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Ni3+/Ni2+ rises from 0.39 to 1.32 and Fe2+/Fe3+ from 0.40 to 1.49. Hydride deprotonates Ni–OH and leaves oxygen vacancies near Fe, making Ni3+ and Fe2+ together. O2 FE is 95.9% (7.48×10−5 mol O2 at 50 mA for 10 min). The trick extends to other TM LDHs.
Methodology
Authors reduced NiFe LDH with NaBH4, quantified Ni/Fe valence by XPS and XAS, mapped oxygen vacancies by EXAFS, and measured OER current and O2 faradaic efficiency.
Limitations
A full electrolyzer lifetime and a complete microkinetic OER mechanism beyond correlating Ni3+ with activity are not provided.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
This library holds 17 empirical chemistry papers on electrochemistry with isolated findings, rates or spectra rather than reviews.
Evidence for the claim as stated.
Treating NiFe layered double hydroxide with NaBH4 lifts Ni3+/Ni2+ from 0.39 to 1.32 and gives 95.9% faradaic efficiency for O2.
Evidence for the claim as stated.
Faradaic efficiency and overpotential trade off; a high FE at impractical potential is not a working electrolyser.
Evidence for the claim as stated.
Valence ratios from XPS/XAS can be the design handle for OER. NaBH₄ reduction of NiFe LDH raises Ni³⁺/Ni²⁺ from 0.39 to 1.32 and Fe²⁺/Fe³⁺ from 0.40 to 1.49, with oxygen vacancies near Fe by EXAFS. O₂ faradaic efficiency is 95.9% (7.48×10⁻⁵ mol O₂ at 50 mA for 10 min). A full electrolyzer lifetime and a complete microkinetic OER cycle are not provided.
Evidence for the claim as stated.
A surface Ni³⁺/Ni²⁺ ratio is a descriptor, not the OER mechanism. NaBH₄-treated LDH correlates Ni³⁺ (0.39 → 1.32) with activity and reports 95.9% O₂ FE, but does not solve the atomic OER cycle. BiOBr's 0.38 mA cm⁻² photocurrent is a different electrochemical question (PEC of a halide film) that XPS characterisation does not make interchangeable with LDH OER.
Evidence for the claim as stated.
NaBH₄-treated NiFe LDH reports a surface-valence descriptor rather than an impedance fit. Ni³⁺/Ni²⁺ rises from 0.39 to 1.32 and Fe²⁺/Fe³⁺ from 0.40 to 1.49; hydride deprotonates Ni–OH and leaves oxygen vacancies near Fe. O₂ faradaic efficiency is 95.9% (7.48×10⁻⁵ mol O₂ at 50 mA for 10 min). A full electrolyzer lifetime and a complete microkinetic OER cycle are not provided — and no Nyquist Rct is in the teaching summary.
Evidence for the claim as stated.
Capacitance-derived ECSA, galvanostatic capacity, and an XPS Ni³⁺ ratio are three different electrochemical claims that students lump as 'impedance showed it was better.' CoP uses 40 μF cm⁻² to normalise HER current (56 mV at 10 mA cm⁻²). Stibnite quotes 455.8 versus 190.1 mA h g⁻¹ after 100 cycles. LDH quotes Ni³⁺/Ni²⁺ 0.39 → 1.32 and 95.9% O₂ FE. Those are not replications of one EIS equivalent circuit.
Evidence for the claim as stated.
Stability means different things, and none is a fitted EIS ageing study in these summaries. CoP claims 20 h HER stability and ~100% FE; stibnite claims 70.8% capacity retention over 100 cycles versus sodium metal; LDH quantifies O₂ for 10 min at 50 mA without an electrolyzer lifetime. A Nyquist plot taken once does not equal those tests.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Faradaic efficiency and overpotential trade off; a high FE at impractical potential is not a working electrolyser.
A surface Ni³⁺/Ni²⁺ ratio is a descriptor, not the OER mechanism. NaBH₄-treated LDH correlates Ni³⁺ (0.39 → 1.32) with activity and reports 95.9% O₂ FE, but does not solve the atomic OER cycle. BiOBr's 0.38 mA cm⁻² photocurrent is a different electrochemical question (PEC of a halide film) that XPS characterisation does not make interchangeable with LDH OER.
- Supports · Bismuth oxyhalide films as photoelectrodes
Capacitance-derived ECSA, galvanostatic capacity, and an XPS Ni³⁺ ratio are three different electrochemical claims that students lump as 'impedance showed it was better.' CoP uses 40 μF cm⁻² to normalise HER current (56 mV at 10 mA cm⁻²). Stibnite quotes 455.8 versus 190.1 mA h g⁻¹ after 100 cycles. LDH quotes Ni³⁺/Ni²⁺ 0.39 → 1.32 and 95.9% O₂ FE. Those are not replications of one EIS equivalent circuit.
- Supports · Ultrathin porous CoP nanosheets drive HER
- Supports · Stibnite in carbon sheets stores sodium better
Stability means different things, and none is a fitted EIS ageing study in these summaries. CoP claims 20 h HER stability and ~100% FE; stibnite claims 70.8% capacity retention over 100 cycles versus sodium metal; LDH quantifies O₂ for 10 min at 50 mA without an electrolyzer lifetime. A Nyquist plot taken once does not equal those tests.
- Supports · Ultrathin porous CoP nanosheets drive HER
- Supports · Stibnite in carbon sheets stores sodium better
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