Combination of atom probe tomography, isotope-labelling and online electrochemical mass spectrometry provides direct correlation of atomic scale structure of Ir oxide catalysts with the mechanism of oxygen formation from the lattice atoms.

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Photocorrosion imposes a fundamental limit to the longevity of devices that harvest energy from photons. As one of the best performing electrode materials for photoelectrochemical water oxidation reaction, BiVO 4 undergoes photocorrosion with various postulated mechanisms under debate. We present time-resolved dissolution measurements to advance the mechanistic understanding, enabled by the recent development in illuminated scanning flow cell coupled to inductively coupled plasma mass spectrometry. The contact dissolution of predominantly V was distinguished from the stoichiometric photoelectrochemical dissolution of Bi and V. The citrate electrolyte was utilized to form soluble complexes with dissolved Bi and to act as hole scavengers that provide photocurrents at a wide range of potentials. The photoelectrochemical dissolution rates remain similar between 0.4 and 1.6 V vs reversible hydrogen electrode and become lower at the open circuit potential, 0.2 V. The time-resolved measurements support oxidation of Bi(III) by photogenerated holes as the main mechanism for photocorrosion.

Photoelectrochemical water splitting is a promising route to produce hydrogen from solar energy. However, corrosion of photoelectrodes remains a fundamental challenge for their implementation. Here, we reveal different dissolution behaviors of BiVO 4 photoanode in pH-buffered borate, phosphate, and citrate (hole-scavenger) electrolytes, studied in operando employing an illuminated scanning flow cell. We demonstrate that decrease in photocurrents alone does not reflect the degradation of photoelectrodes. Changes in dissolution rates correlate to the evolution of surface chemistry and morphology. The correlative measurements on both sides of the liquid–semiconductor junction provide quantitative comparison and mechanistic insights into the degradation processes.