Youn Jeong Jang

Selective CO production by Au coupled ZnTe/ZnO in the photoelectrochemical CO2 reduction system

A gold-coupled ZnTe/ZnO-nanowire array is a new photocathode for selective CO2 reduction to CO. At −0.7 VRHE under simulated 1 sun illumination, its photocurrent (−16.0 mA cm−2) and incident photon-to-current conversion efficiency (97%) represent the highest among reported ZnTe photocathodes for CO2 reduction and dramatic enhancement from those of a bare electrode (−7.9 mA cm−2, 68%). In addition, the Au nanoparticles convert mainly-hydrogen-producing bare ZnTe/ZnO-nanowires into mainly-CO-producing photocathodes in photoelectrochemical CO2 reduction. The remarkable effects of the Au co-catalyst originate from the formation of a Schottky junction with ZnTe to improve charge separation and to provide reaction centers for CO2 reduction suppressing competing water reduction.

Aqueous‐Solution Route to Zinc Telluride Films for Application to CO2 Reduction

As a photocathode for CO2 reduction, zinc-blende zinc telluride (ZnTe) was directly formed on a Zn/ZnO nanowire substrate by a simple dissolution-recrystallization mechanism without any surfactant. With the most negative conduction-band edge among p-type semiconductors, this new photocatalyst showed efficient and stable CO formation in photoelectrochemical CO2 reduction at -0.2--0.7 V versus RHE without a sacrificial reagent.

Unbiased Sunlight-Driven Artificial Photosynthesis of Carbon Monoxide from CO2 Using a ZnTe-Based Photocathode and a Perovskite Solar Cell in Tandem

Solar fuel production, mimicking natural photosynthesis of converting CO2 into useful fuels and storing solar energy as chemical energy, has received great attention in recent years. Practical large-scale fuel production needs a unique device capable of CO2 reduction using only solar energy and water as an electron source. Here we report such a system composed of a gold-decorated triple-layered ZnO@ZnTe@CdTe core-shell nanorod array photocathode and a CH3NH3PbI3 perovskite solar cell in tandem. The assembly allows effective light harvesting of higher energy photons (>2.14 eV) from the front-side photocathode and lower energy photons (>1.5 eV) from the back-side-positioned perovskite solar cell in a single-photon excitation. This system represents an example of a photocathode-photovoltaic tandem device operating under sunlight without external bias for selective CO2 conversion. It exhibited a steady solar-to-CO conversion efficiency over 0.35% and a solar-to-fuel conversion efficiency exceeding 0.43% including H2 as a minor product.

Solar Hydrogen Production from Zinc Telluride Photocathode Modified with Carbon and Molybdenum Sulfide.

A zinc telluride (ZnTe) film modified with MoS2 and carbon has been studied as a new photocathode for solar hydrogen production from photoelectrochemical (PEC) water splitting. The modification enhances PEC activity and stability of the photocathode. Thus, the MoS2/C/ZnTe/ZnO electrode exhibits highly improved activity of -1.48 mA cm(-2) at 0 VRHE with a positively shifted onset potential up to 0.3 VRHE relative to bare ZnO/ZnTe electrode (-0.19 mA cm(-2), 0.18 VRHE) under the simulated 1 sun illumination. This represents the highest value ever reported for ZnTe-based electrodes in PEC water splitting. The carbon densely covers the surface of ZnTe to protect it against photocorrosion in aqueous electrolyte and improves charge separation. In addition, MoS2 further enhances the PEC performance as a hydrogen evolution co-catalyst.

Correction: Selective CO production by Au coupled ZnTe/ZnO in the photoelectrochemical CO2 reduction system

Correction for ‘Selective CO production by Au coupled ZnTe/ZnO in the photoelectrochemical CO2 reduction system’ by Youn Jeong Jang et al., Energy Environ. Sci., 2015, 8, 3597–3604.

Sodium-Containing Spinel Zinc Ferrite as a Catalyst Precursor for the Selective Synthesis of Liquid Hydrocarbon Fuels.

A microwave-assisted hydrothermal synthesis produces ZnFe2 O4 containing Na residue as a precursor to a CO2 hydrogenation catalyst that displays high CO2 conversion and high selectivity to liquid hydrocarbon products in the gasoline and diesel range with high olefin-to-paraffin ratios. Compared to reference catalysts derived from Fe2 O3 and a ZnO-Fe2 O3 physical mixture, the ZnFe2 O4 -derived catalyst contains well-dispersed iron particles with Zn serving as a structural promoter. A profound effect of the residual Na as an electronic promoter is also observed, which improves the selectivity for C5+ hydrocarbons and olefins. The ZnFe2 O4 -derived catalyst exhibits excellent performance in the CO2 Fischer-Tropsch reaction as it forms the active Hägg iron carbide (χ-Fe5 C2 ) phase readily through the in situ carburization of iron.