We bundle our expertise in heterogeneous and molecular catalyst design further towards photoelectrochemical (PEC) systems. Following our 3d transition metal thread, we explored fundamentally unresolved issues of photoanode design for hematite (α-Fe2O3) as a low-cost and promising material.


Nat. Commun2021 (12) 255 

Specifically, we zoomed in on understanding the function of surface states whose role in the OER process is still controversially debated. We focused on the two surface states of hematite (S1 and S2) and their reaction kinetics as well as their dynamic interactions under simulated solar irradiation and real operational conditions, covering a wide range of experimental parameters (potential, light intensity, pH…). Two complementary techniques, namely PEIS and TPS, provided new insight into the hitherto unassigned chemical identity of S2 through detailed kinetic analyses. For the first time, we could assign S2 to an iron-peroxo OER intermediate based on a wide range of data sets and monitor its kinetic interplay with S1. These results highlighted enhanced oxo species migration on photoanode surfaces as a key optimization parameter (Nat. Commun. 2021 (12) 255).


J. Am. Chem. Soc. 2019, 141, 32, 12839–12848

We also combined our expertise on cubane catalysts and hematite monitoring to address the controversial role of molecular co-catalysts, which keep attracting attention for photoanode optimization. Complementary PEIS/TPS monitoring of hematite photoanodes loaded with several {Co(II)4O4} cubanes shed new light on the dynamic role of molecular co-catalysts. We discovered that they change their roles from hole reservoirs to active catalytic centers as a function of the applied bias. In line with hematite surface states, stabilization of high valent metal-oxo species was identified as an overarching design guideline (J. Am. Chem. Soc. 2019, 141, 12839).


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