Plasmon-enhanced Water Splitting Research Articles

Solar-driven plasmonic heterostructure Ti/TiO2-x with gradient doping for sustainable plasmon-enhanced catalysis.

Plasmon-enhanced harvesting of photons has contributed to the photochemical conversion and storage of solar energy. However, high dependence on noble metals and weak coupling in heterostructures constrain the progress towards sustainable plasmonic enhancement. Here earth-abundant Ti is studied to achieve the plasmonic enhancement of catalytic activity in a solar-driven heterostructure Ti/TiO2-x. The heterostructure was fabricated by engineering an intense coupling of a surface-etched Ti metal and a gradient-based TiO2-x dielectric via diffusion doping. Ti/TiO2-x exhibits a highly resonant light absorption band associated with surface plasmon resonances that exhibit strong near-field enhancement (NFE) and hot electron injection effects. In a photoelectrochemical system, intense interaction of the resonant plasmons with a vicinal TiO2-x dielectric accelerates the transfer of solar energy to charge carriers for plasmon-enhanced water splitting reactions. Moreover, the plasmonic Ti/TiO2-x structure presents sustained enhanced redox activities over 100 h. The intense coupling by gradient doping offers an effective approach to enable the plasmon resonances of Ti excited by visible light. The Ti-based plasmonic heterostructure potentially opens an alternative avenue towards sustainable plasmon-enhanced catalysis.

Plasmon-enhanced Water Splitting Utilizing the Heterojunction Synergistic Effect between SrTiO3 and Rutile-TiO2

Abstract A plasmon-enhanced water splitting system using a gold nanostructured strontium titanate (SrTiO3) single-crystal photoelectrode with a titanium dioxide (TiO2) thin film heterojunction was developed. Simultaneous evolution of hydrogen and oxygen was observed in separate reaction chambers under visible light irradiation. The substrate composed of single-crystal SrTiO3 with a rutile TiO2 thin film heterojunction exhibited enhanced water splitting activity compared with the electrode without the TiO2 thin film because the synergistic effect may prevent the back-electron-transfer reaction.

Plasmon enhanced water splitting mediated by hybrid bimetallic Au-Ag core-shell nanostructures.

In this work, we employed wet chemically synthesized bimetallic Au-Ag core-shell nanostructures (Au-AgNSs) to enhance the photocurrent density of mesoporous TiO2 for water splitting and we compared the results with monometallic Au nanoparticles (AuNPs). While Au-AgNSs incorporated photoanodes give rise to 14× enhancement in incident photon to charge carrier efficiency, AuNPs embedded photoanodes result in 6× enhancement. By varying nanoparticle concentration in the photoanodes, we observed ∼245× less Au-AgNSs are required relative to AuNPs to generate similar photocurrent enhancement for solar fuel conversion. Power-dependent measurements of Au-AgNSs and AuNPs showed a first order dependence to incident light intensity, relative to half-order dependence for TiO2 only photoanodes. This indicated that plasmonic nanostructures enhance charge carriers formed on the surface of the TiO2 which effectively participate in photochemical reactions. Our experiments and simulations suggest the enhanced near-field, far-field, and multipolar resonances of Au-AgNSs facilitating broadband absorption of solar radiation collectively gives rise to their superior performance in water splitting.

Enhanced electrocatalytic activity for hydrogen evolution reaction from self-assembled monodispersed molybdenum sulfidenanoparticles on an Au electrode

Ultrasmall molybdenum sulfide nanoparticles with diameters of 1.47 ± 0.16 nm were fabricated from bulk MoS2 by a combination of ultrasonication and centrifugation. The nanoparticles were then assembled on an Au surface to form a film with high electrocatalytic activity for hydrogen evolution reaction (HER). A Tafel slope of 69 mV per decade was measured for this film and the onset potential was estimated to be −0.09 V. The small loading (1.03 μg cm−2) and the high current density (0.92 mA cm−2 at η = 0.15 V) demonstrated extremely high catalytic efficiency. X-ray photoelectron spectroscopic results revealed that the assembled nanoparticle film was sulfur enriched with abundant S edges and a structural rearrangement of the S rich particles might occur during the self-assembly process, resulting in significantly enhanced electrocatalytic activity for HER. Electrochemical impedance measurements suggested that the assembling process optimized the conductivity of the nanoparticle film, which contributed to the enhanced HER catalytic activity. Our research has provided a new way to synthesize active molybdenum sulfide nanoparticles for HER and a new approach to achieve enrichment of S edges on molybdenum sulfide, which might have potential use not only for electrocatalytic HER, but also for photoelectrocatalytic HER and plasmon-enhanced water splitting.

Plasmonic solar water splitting

The study of the optoelectronic effects of plasmonic metal nanoparticles on semiconductors has led to compelling evidence for plasmon-enhanced water splitting. We review the relevant physics, device geometries, and research progress in this area. We focus on localized surface plasmons and their effects on semiconductors, particularly in terms of energy transfer, scattering, and hot electron transfer.