The development of upscalable oxygen
evolving electrocatalysts from earth-abundant metals able to operate
in neutral or acidic environments and low overpotentials remains a
fundamental challenge for the realization of artificial photosynthesis.
In this study, we report a highly active phase of heterobimetallic
cyanide-bridged electrocatalysts able to promote water oxidation under
neutral, basic (pH < 13), and acidic conditions (pH > 1). Cobalt–iron
Prussian blue-type thin films, formed by chemical etching of Co(OH)1.0(CO3)0.5·nH2O nanocrystals, yield a dramatic enhancement of the catalytic
performance toward oxygen production, when compared with previous
reports for analogous materials. Electrochemical, spectroscopic, and
structural studies confirm the excellent performance, stability, and
corrosion resistance, even when compared with state-of-the-art metal
oxide catalysts under moderate overpotentials and in a remarkably
large pH range, including acid media where most cost-effective water
oxidation catalysts are not useful. The origin of the superior electrocatalytic
activity toward water oxidation appears to be in the optimized interfacial
matching between catalyst and electrode surface obtained through this
fabrication method.
Atom-thin transition metal dichalcogenides (TMDs) have emerged as fascinating materials and key structures for electrocatalysis. So far, their edges, dopant heteroatoms and defects have been intensively explored as active sites for the hydrogen evolution reaction (HER) to split water. However, grain boundaries (GBs), a key type of defects in TMDs, have been overlooked due to their low density and large structural variations. Here, we demonstrate the synthesis of wafer-size atom-thin TMD films with an ultra-high-density of GBs, up to ~1012 cm−2. We propose a climb and drive 0D/2D interaction to explain the underlying growth mechanism. The electrocatalytic activity of the nanograin film is comprehensively examined by micro-electrochemical measurements, showing an excellent hydrogen-evolution performance (onset potential: −25 mV and Tafel slope: 54 mV dec−1), thus indicating an intrinsically high activation of the TMD GBs.
Titanium improves water oxidation yields over hematite photoanodes, tailoring its surface state density (kinetics) and hematite-pseudobrookite heterojunctions (energetics).
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