Spectrally Resolved Single Particle Photoluminescence Microscopy Reveals Heterogeneous Photocorrosion Activity of Cuprous Oxide Microcrystals

Abstract

Photocorrosion of cuprous oxide (Cu2O) has notably limited its application as an efficient photocatalyst. We report a facile approach to visualize in situ formation of copper and oxygen vacancies on the Cu2O surface under ambient condition. By imaging photoexcited single Cu2O particles, the resultant photoluminescence generated at Cu2O surface enable effective localization of copper and oxygen vacancies. Single particle photoluminescence imaging showed substantial heterogeneity in the rate of defect formation at different facets with the truncated corners achieving the fastest initial rate of photooxidation before subsequently changing to the face and edge sites as the photocorrosion proceeds. The generation of copper or oxygen vacancy is proportional to the photoexcitation power, while pH-dependent studies rationalized alkaline conditions for the formation of copper vacancy. Reaction in an electron–hole scavenger system showed that photooxidation and photoreduction will simultaneously occur, yet heterogeneously on the surface of Cu2O, with rate of copper vacancy formation being fastest.

Understanding Photo(electro)catalysts for Energy Conversion via Operando Functional Imaging

“…Another study also utilized single-particle photoluminescence microscopy to investigate defects, revealing heteroge-neous photocorrosion activity on Cu 2 O. 49 The emission of photoluminescence photons at 615, 710, 820, and 900 nm arises from distinct recombination processes involving photoexcited electrons, valence band holes, and vacancies in Cu 2 O. Specifically, the 615 nm emission results from electron−hole recombination in the bands, the 710 and 820 nm emissions arise from doubly ionized (VO 2+ ) and singly ionized (VO + ) oxygen vacancies, and the 900 nm emission stems from copper vacancies (V Cu ).…”

“…Another study also utilized single-particle photoluminescence microscopy to investigate defects, revealing heterogeneous photocorrosion activity on Cu 2 O . The emission of photoluminescence photons at 615, 710, 820, and 900 nm arises from distinct recombination processes involving photoexcited electrons, valence band holes, and vacancies in Cu 2 O.…”

Nanoscale Luminescence Imaging/Detection of Single Particles: State-of-the-Art and Future Prospects

“…131 Likewise, single-particle PL microscopy has been reported for investigating the defects of single Cu 2 O microcrystals, revealing their corresponding heterogeneous photocorrosion activity (Figure 7c, d). 132 Understanding the photogenerated hole and electron pair behavior, photocatalytic active sites, and reaction processes on a single particle (catalyst) level is promising for developing efficient catalysts. In particular, titanium oxide (TiO 2 ) with various morphologies and different crystal structures has been documented as a powerful photocatalyst for diverse catalytic processes due to its high reactivity, nontoxicity, and chemical stability.…”

“…(c, d) PL images of single Cu 2 O microcrystals over different periods of time for revealing their corresponding heterogeneous photocorrosion activity. Reprinted from ref from American Chemical Society, copyright 2022, .…”

Spatial separation of photogenerated charges on the anisotropic facets of cuprous oxide

“…27,28 However, the charge separation capability of Cu 2 O is poor, which strongly limits its solar energy conversion efficiencies and further potential applications. 29,30 It has been reported that Cu 2 O crystals with different exposed facets show various photocatalytic performances, [31][32][33] for instance, cubic Cu 2 O with {100} facets shows a lower performance in photocatalytic H 2 evolution than rhombic dodecahedral Cu 2 O with {110} facets. 34 In addition, {100} and {110} facets were considered more unstable than the {111} facet under a photocatalytic process.…”