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.

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What mesocrystals were made?

(NiFe)S2 pyrite porous cubes, nearly single-crystalline.

What is the particle size?

About 40–50 nm.

How are they synthesized?

Ni(NO3)2 and thioacetamide in oleylamine heated at 180 °C.

What growth mechanism?

Non-classical aggregation of <2 nm clusters, not classical ion-by-ion growth.

What happens at 140 °C vs 180 °C?

PCs are poorly defined and clusters still add on; 180 °C gives 40–50 nm PCs in 30 min.

η10 of Fe-doped PCs?

Less than 260 mV at 10 mA cm–2 on GCE.

η10 of undoped PC-1?

351 mV after iR correction.

What is the true OER material?

Amorphous S-doped metal (oxy)hydroxides after reconstruction.

Does Fe help keep sulfur?

Yes—after η = 300 mV, 1 h, remaining S is higher with more Fe.

What happens to undoped PCs after CV?

Cubes are destroyed into irregular particles and nanowires.

Pyrite space group?

Pa3, face-centered cubic.