Zhiqi Huang

Sorption enhanced steam reforming of ethanol on Ni–CaO–Al2O3 multifunctional catalysts derived from hydrotalcite-like compounds

This paper describes the sorption of carbon dioxide for enhanced steam reforming of ethanol to produce hydrogen via Ni–CaO–Al2O3 multifunctional catalysts derived from hydrotalcite-like compounds (HTlcs). The catalysts were characterized by N2 adsorption–desorption, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR) and thermogravimetric analysis (TGA) and tested in sorption enhanced steam reforming of ethanol (SESRE), in which products were monitored by an online mass spectrometer (MS). The Ni–CaO–Al2O3 catalysts possess uniform distribution of Ni, Ca and Al, contributing significantly to the excellent CO2 adsorbent capacity and reforming activity in SESRE. We have also examined the effect of Ca/Al ratios on Ni dispersion, CaO particle size, and catalytic reactivity; a Ca/Al of 3.0 was optimized. The Ni–CaO–Al2O3 catalysts outperform the conventional mixture of CaO adsorbents and Ni/Al2O3 catalysts for SESRE.

N-doped Ag/TiO2 hollow spheres for highly efficient photocatalysis under visible-light irradiation

This paper describes the synthesis of TiO2 hollow spheres (HSs) modified via nitrogen doping and silver loading (Ag–N–TiO2) with particle diameters of ~100 nm. The specific surface area of the Ag–N–TiO2 was up to 147 m2 g−1 and this structure is stable upon high temperature treatment. Ag–N–TiO2 exhibited excellent photocatalytic activity for the degradation of dye compounds under visible light irradiation (≥410 nm) due to their larger surface area and controlled morphology compared with previously reported N-doped TiO2 fine particles (e.g. N–P25).

Thin Heterojunctions and Spatially Separated Cocatalysts To Simultaneously Reduce Bulk and Surface Recombination in Photocatalysts

Efficient charge separation and light absorption are crucial for solar energy conversion over solid photocatalysts. This paper describes the construction of Pt@TiO2 @In2 O3 @MnOx mesoporous hollow spheres (PTIM-MSs) for highly efficient photocatalytic oxidation. TiO2 -In2 O3 double-layered shells were selectively decorated with Pt nanoparticles and MnOx on the inner and outer surfaces, respectively. The spatially separated cocatalysts drive electrons and holes near the surface to flow in opposite directions, while the thin heterogeneous shell separates the charges generated in the bulk phase. The synergy between the thin heterojunctions and the spatially separated cocatalysts can simultaneously reduce bulk and surface/subsurface recombination. In2 O3 also serves as a sensitizer to enhance light absorption. The PTIM-MSs exhibit high photocatalytic activity for both water and alcohol oxidation.

Surviving High-Temperature Calcination: ZrO2-Induced Hematite Nanotubes for Photoelectrochemical Water Oxidation

Nanotubular Fe2 O3 is a promising photoanode material, and producing morphologies that withstand high-temperature calcination (HTC) is urgently needed to enhance the photoelectrochemical (PEC) performance. This work describes the design and fabrication of Fe2 O3 nanotube arrays that survive HTC for the first time. By introducing a ZrO2 shell on hydrothermal FeOOH nanorods by atomic layer deposition, subsequent high-temperature solid-state reaction converts FeOOH-ZrO2 nanorods to ZrO2 -induced Fe2 O3 nanotubes (Zr-Fe2 O3 NTs). The structural evolution of the hematite nanotubes is systematically explored. As a result of the nanostructuring and shortened charge collection distance, the nanotube photoanode shows a greatly improved PEC water oxidation activity, exhibiting a photocurrent density of 1.5 mA cm-2 at 1.23 V (vs. reversible hydrogen electrode, RHE), which is the highest among hematite nanotube photoanodes without co-catalysts. Furthermore, a Co-Pi decorated Zr-Fe2 O3 NT photoanode reveals an enhanced onset potential of 0.65 V (vs. RHE) and a photocurrent of 1.87 mA cm-2 (at 1.23 V vs. RHE).

Edge Sites with Unsaturated Coordination on Core–Shell Mn3O4@MnxCo3−xO4 Nanostructures for Electrocatalytic Water Oxidation

Transition-metal oxides are extensively investigated as efficient electrocatalysts for the oxygen evolution reaction (OER). However, large-scale applications remain challenging due to their moderate catalytic activity. Optimized regulation of surface states can lead to improvement of catalytic properties. Here, the design of Mn@Cox Mn3-x O4 nanoparticles with abundant edge sites via a simple seed-mediated growth strategy is described. The unsaturated coordination generated on the edge sites of Cox Mn3-x O4 shells makes a positive contribution to the surface-structure tailoring. Density functional theory calculations indicate that the edge sites with unsaturated coordination exhibit intense affinity for OH- in the alkaline electrolyte, which greatly enhances the electrochemical OER performance of the catalysts. The resulting Mn@Cox Mn3-x O4 catalysts yield a current density of 10 mA cm-2 at an overpotential of 246 mV and a relatively low Tafel slope of 46 mV dec-1 . The successful synthesis of these metal oxides nanoparticles with edge sites may pave a new path for rationally fabricating efficient OER catalysts.

Morphological and Compositional Design of Pd–Cu Bimetallic Nanocatalysts with Controllable Product Selectivity toward CO2 Electroreduction

Electrochemical conversion of carbon dioxide (electrochemical reduction of carbon dioxide) to value-added products is a promising way to solve CO2 emission problems. This paper describes a facile one-pot approach to synthesize palladium-copper (Pd-Cu) bimetallic catalysts with different structures. Highly efficient performance and tunable product distributions are achieved due to a coordinative function of both enriched low-coordinated sites and composition effects. The concave rhombic dodecahedral Cu3 Pd (CRD-Cu3 Pd) decreases the onset potential for methane (CH4 ) by 200 mV and shows a sevenfold CH4 current density at -1.2 V (vs reversible hydrogen electrode) compared to Cu foil. The flower-like Pd3 Cu (FL-Pd3 Cu) exhibits high faradaic efficiency toward CO in a wide potential range from -0.7 to -1.3 V, and reaches a fourfold CO current density at -1.3 V compared to commercial Pd black. Tafel plots and density functional theory calculations suggest that both the introduction of high-index facets and alloying contribute to the enhanced CH4 current of CRD-Cu3 Pd, while the alloy effect is responsible for high CO selectivity of FL-Pd3 Cu.