Plasmonic CoO-Decorated Au Nanorods for Photoelectrocatalytic Water Oxidation

Abstract

Harvesting the full bandwidth of the solar spectrum, especially the near-infrared portion, remains a challenge for solar-to-fuel conversion technology. Plasmonic nanostructures have recently attracted attention in this connection due to their enhanced yet tunable broadband absorption and photochemical stability. Here we report a nanoplasmonic photocatalytic construct by decorating plasmonic Au nanorods with CoO for harvesting visible and NIR light via the photoelectrochemical water oxidation reaction (WOR). In contrast to previous reports of plasmonic photocatalyst constructs, our structure does not require complicated fabrication or rely on rare-earth heavyatom elements and exhibits excellent photostability without leaching of either cobalt or gold into the reaction solution under photoelectrochemical conditions. This catalytic construct triggered photoelectrochemical WOR with the generation of significant photocurrent (∼100 μA cm −2 ) while producing photogenerated oxygen at 18.1 mmol h −1 and hydrogen at 40.2 mmol h −1 (on the counter electrode) per milligram of cobalt under broadband excitation of 410−1700 nm with photon-tooxygen conversion efficiency of ∼0.05% in neutral aqueous conditions. The broadband photocatalytic activity of CoOdecorated Au nanorods was attributed to the hot holes generated by the photoexcitation of plasmonic gold nanorods.

Gold Nanorods: The Most Versatile Plasmonic Nanoparticles

“…The formation of metal oxide shells mainly involves the nucleation, growth, or crystallization of metal oxide precursors on Au NRs. Reducing agents such as AA and HQ can directly react with the precursor to form semiconductor NPs on the Au NR surface through Ostwald ripening. , Several types of metal oxide shells are produced by the reduction or the hydrolysis of the precursor. For example, the preparation of (Au NR core)@(MnO 2 shell) nanostructures undergoes the ligand exchange with PEG-SH and the reduction of KMnO 4 .…”

“…Owing to the widely adjustable l-SPR frequency of Au NRs, the combination of Au NRs and semiconductors can greatly expand the responsive range of semiconductor photocatalysts and thereby increase the efficiency of photocatalysis. Some studies take advantage of the heat generated from Au NRs upon plasmon excitation. ,, Some works employ Au NRs not for direct photocatalysis but for powering photoelectrochemical reactions. ,,, The incident light is first converted to electricity, which is in turn used to power electrochemical reactions. The representative works on Au-NR-enabled photocatalysis from 2013 are summarized in Table .…”

“…533,1150,1153 Some works employ Au NRs not for direct photocatalysis but for powering photoelectrochemical reactions. 420,430,1154,1155 The incident light is first converted to electricity, which is in turn used to power electrochemical reactions. The representative works on Au-NR-enabled photocatalysis from 2013 are summarized in Table 4.…”

BiVO4 Microparticles Decorated with Cu@Au Core-Shell Nanostructures for Photocatalytic H2O2 Production

“…Based on the above analysis, in this work, selective modification of the Cu@Au core-shell nanostructured cocatalyst on the electron-enriched (010) facet of the BiVO 4 microparticle was synthesized by selective photodeposition of low-cost Cu nanoparticles and subsequent in situ galvanic displacement of Cu by the nano-Au cocatalyst, where metallic Cu nanocore facilitates the photogenerated electron transfer of BiVO 4 and simultaneously reduces the negative charge density of the Au nanoshell. − Specifically, owing to the low work function of Cu (Φ Cu = 4.7 eV), the ohmic contact can be formed between Cu and BiVO 4 (Φ BiVO4 = 4.9 eV) to effectively transfer the photogenerated electrons. − Then, the photogenerated electrons are transferred from the inner Cu to the outermost Au where the catalytic reaction of two-electron O 2 reduction takes place. Meanwhile, owing to the ohmic contact between Cu and BiVO 4 , negative charge accumulation of the nano-Au cocatalyst in Cu@Au/BiVO 4 is less than that in Au/BiVO 4 , and even positive charge accumulation of the nano-Au cocatalyst is possible in Cu@Au/BiVO 4 (Figure D), which could generate stronger adsorption of O 2 and HOO* on the Au surface of Cu@Au/BiVO 4 and thus accelerate its catalytic activity for two-electron O 2 reduction to H 2 O 2 (Figure C). − In addition, our strategy of crystal engineering and selective modification of nano-cocatalyst for the BiVO 4 photocatalyst can achieve directional transport of photogenerated carriers and effectively catalytic activity sites to accelerate the photocatalytic H 2 O 2 production.…”

Silver-Copper Oxide Heteronanostructures for the Plasmonic-Enhanced Photocatalytic Oxidation of N-Hexane in the Visible-NIR Range

“…The reduced dimensions of the heteronanostructures minimize the probability of undergoing another relaxation/recombination process [68]. While the injection of hot electrons (using n-type semiconductors such as TiO 2 ) is the most accepted plasmon-driven charge transfer mechanism, there exist recent interesting studies claiming the importance of hot holes in other plasmonic-based systems [73,86,92,97,134,135,136,137] such as Au-NiO x , Au-pGaN [73], Au nanorods coated with a CoO nanoshell [138], Au nanostructures [101,139,140], or Ag-BiOCl hybrids [86,137].…”