Pyrite mesocrystals reconstruct into OER catalysts
Oleylamine-grown (NiFe)S2 porous cubes form by cluster aggregation; Fe-doped samples reach η10 < 260 mV after converting to S-doped (oxy)hydroxides.
Source
The formation of (NiFe)S<sub>2</sub> pyrite mesocrystals as efficient pre-catalysts for water oxidation
Study at a glance
- Design
- Other — NiFeS2 pyrite mesocrystal growth and OER pre-catalyst evaluation
- N
- Materials synthesis and electrocatalysis — no sample N
- Population
- Fe-doped NiS2 pyrite mesocrystals on GCEs
- Outcome
- OER overpotential and post-CV transformation to active (oxy)hydroxide
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Inspect source passages
Pyrite mesocrystals reconstruct into OER catalysts
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
Fe-doped PCs showed η10 less than 260 mV on GCEs.
As for the OER performance, the Fe-doped PCs showed an overpotential ( η ) of less than 260 mV to reach a current density of 10 mA cm –2 ( η 10 ) on glassy carbon electrodes (GCEs).
PC-1 showed an η10 of 351 mV with iR correction.
PC-1 showed an η 10 of 351 mV (with iR correction, where solution resistance was obtained by impedance analysis, Fig.
What they did
Authors heated Ni(NO3)2/TAA in oleylamine, doped Fe, used TEM/SAED to map mesocrystal growth, then measured OER and post-CV spectroscopy.
What they found
40–50 nm nearly single-crystalline porous cubes grow from <2 nm clusters at 180 °C. Fe-doped PCs have η10 < 260 mV vs 351 mV for NiS2. After CVs the real catalyst is amorphous S-doped metal (oxy)hydroxide; Fe helps retain S.
The limits
What it doesn't show
Atomic OER cycle on the reconstructed surface is not solved; GCE η10 is not a device metric.
Key terms
- Mesocrystal
- Crystal of aligned nanocrystal building blocks with a common orientation.
- OER
- Oxygen evolution reaction, 4OH– → O2 + 2H2O + 4e– in alkali.
- Pre-catalyst
- As-synthesized phase that reconstructs into the true active material under anodic bias.
- η10
- Overpotential needed for 10 mA cm–2.
- Pyrite
- MS2 structure (Pa3) used here as (NiFe)S2.
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Growth mode of the PCs:
Common questions
How do the cubes grow?
Non-classical aggregation of <2 nm nickel sulfide clusters.
What is the working OER phase?
Amorphous S-doped metal (oxy)hydroxide after CV.
Role of Fe?
Lowers η10 and helps retain S under anodic conditions.
NiS2-only η10?
351 mV vs <260 mV with Fe.
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