Charlene Ng

Transforming Anodized WO3 Films into Visible-Light-Active Bi2WO6 Photoelectrodes by Hydrothermal Treatment

We directly transformed anodized tungsten oxide film (WO3·2H2O) into bismuth tungstate (Bi2WO6) by substituting the intercalated water molecules with [Bi2O2](2+) in a hydrothermal treatment. The resultant Bi2WO6 was readily used as an electrode to produce anodic photocurrent in H2 evolution on the Pt counter electrode observed under visible light irradiation.

Influence of annealing temperature of WO3 in photoelectrochemical conversion and energy storage for water splitting.

The current work demonstrates the importance of WO3 crystallinity in governing both photoenergy conversion efficiency and storage capacity of the flower structured WO3 electrode. The degree of crystallinity of the WO3 electrodes was varied by altering the calcination temperature from 200 to 600 °C. For the self-photochargeability phenomenon, the prevailing flexibility of the short-range order structure at low calcination temperature of 200 °C favors the intercalation of the positive cations, enabling more photoexcited electrons to be stored within WO3 framework. This leads to a larger amount of stored charges that can be discharged in an on-demand manner under the absence of irradiation for H2 generation. The stability of the electrodes calcined at 200 °C, however, is compromised because of the structural instability caused by the abundance insertion of cations. On the other hand, films that were calcined at 400 °C displayed the highest stability toward both intercalation of the cations and photoelectrochemical water splitting performance. Although crystallinty of WO3 was furthered improved at 600 °C heat treatment, the worsened contact between the WO3 platelets and the conducting substrate as induced by the significant sintering has been more detrimental toward the charge transport.

TiO2-supported copper nanoparticles prepared via ion exchange for photocatalytic hydrogen production

Ion exchange (IE) has been used to prepare Cu/TiO2 for photocatalytic hydrogen generation. The IE Cu/TiO2 particles comprised a mixture of large and fine copper/copper oxide deposits which were well dispersed across the TiO2 surface. Hydrogen generation photoactivity by the IE Cu/TiO2 was ∼44% greater than the activity displayed by Cu/TiO2 prepared via wet impregnation (WI) at a similar copper loading. Temperature programmed reduction studies indicated the IE Cu/TiO2 possessed a greater portion of highly dispersed fine copper deposits than the WI Cu/TiO2 which may account for the higher photoactivity. The hydrogen generation activity of IE Cu/TiO2 was maintained over three 5 h reaction cycles.

Understanding Self‐Photorechargeability of WO3 for H2 Generation without Light Illumination

This work presents insight into the self-photorechargeability of WO(3), whereby the intercalation of positive alkali cations is accompanied by the simultaneous storage of photo-excited electrons. The cyclic voltammetry studies verify the photo-assisted intercalation and de-intercalation of Na(+) and K(+) from the flower structured WO(3). A storage capacity of up to 0.722 C cm(-2) can be achieved in a saturated (0.68 M) K(2)SO(4) electrolyte solution. However, the best photo recharge-discharge stability of the electrode are observed at a lower (0.1 M) cation concentration. At high electrolyte concentrations, the intercalated cations are firmly trapped, as indicated by the structural modifications observed in Raman analysis, resulting in much less photocharging and discharging abilities in subsequent cycles. The study also shows that the stored electrons can be successfully used to generate H(2) with 100 % faradaic efficiency in the absence of light.

A dual-electrolyte system for photoelectrochemical hydrogen generation using CuInS2-In2O3-TiO2 nanotube array thin film

The utilization of Na2S/Na2SO3 mixture as the electrolyte solution to stabilize sulfide anode in a photoelectrochemical cell for hydrogen evolution generally compromises the current-to-hydrogen efficiency (η-current) of the system. Here, the employment of a dual-electrolyte system, that is, Na2S/Na2SO3 mixture and pH-neutral Na2SO4 as the respective electrolyte solutions in the anode and cathode chambers of a water splitting cell is demonstrated to suppress the photocorrosion of CuInS2-In2O3-TiO2 nanotube (CIS-In2O3-TNT) heterostructure, while simultaneously boosts the η-current. Although n-type CIS and In2O3 nanoparticles can be easily formed on TNT array via facile pulse-assisted electrodeposition method, conformal deposition of the nanoparticles homogeneously on the nanotubes wall with preservation of the TNT hollow structure is shown to be essential for achieving efficient charge generation and separation within the heterostructure. In comparison to Na2S/Na2SO3 solution as the sole electrolyte in both the anode and cathode chambers, introduction of dual electrolyte is shown to not only enhance the photostability of the CIS-In2O3-TNT anode, but also lead to near-unity η-current as opposed to the merely 20% η-current of the single-electrolyte system.摘要光电化学电池产氢过程中利用 Na2S/Na2SO3混合物作为电解质溶液稳定硫化物阳极通常会牺牲电流产氢效率(ηcurrent). 本文采用Na2S/Na2SO3和pH中性的Na2SO4分别作为光解水电池的阳极和阴极电解液可有效抑制CuInS2-In2O3-TiO2 (CIS-In2O3-TNT)纳米管杂化结构的光腐蚀, 同时提高ηcurrent. 通过脉冲辅助电沉积法可将n型CIS和In2O3纳米粒子沉积在TNT阵列表面, 在保留TNT原有中空结构的前提下将纳米粒子均匀沉积在纳米管上对于在杂化结构中获得高效电荷聚集和分离非常必要. 与Na2S/Na2SO3单电解液电池相比双电解液的引入不仅提高了CIS-In2O3-TNT阳极的光稳定性, 而且ηcurrent接近于1并远高于单电解液电池(20%).

Understanding self-photorechargeability of WO(3) for H(2) generation without light illumination.

This work presents insight into the self-photorechargeability of WO(3), whereby the intercalation of positive alkali cations is accompanied by the simultaneous storage of photo-excited electrons. The cyclic voltammetry studies verify the photo-assisted intercalation and de-intercalation of Na(+) and K(+) from the flower structured WO(3). A storage capacity of up to 0.722 C cm(-2) can be achieved in a saturated (0.68 M) K(2)SO(4) electrolyte solution. However, the best photo recharge-discharge stability of the electrode are observed at a lower (0.1 M) cation concentration. At high electrolyte concentrations, the intercalated cations are firmly trapped, as indicated by the structural modifications observed in Raman analysis, resulting in much less photocharging and discharging abilities in subsequent cycles. The study also shows that the stored electrons can be successfully used to generate H(2) with 100 % faradaic efficiency in the absence of light.

Understanding Self-Photorechargeability of WO3for H2Generation without Light Illumination

This work presents insight into the self-photorechargeability of WO(3), whereby the intercalation of positive alkali cations is accompanied by the simultaneous storage of photo-excited electrons. The cyclic voltammetry studies verify the photo-assisted intercalation and de-intercalation of Na(+) and K(+) from the flower structured WO(3). A storage capacity of up to 0.722 C cm(-2) can be achieved in a saturated (0.68 M) K(2)SO(4) electrolyte solution. However, the best photo recharge-discharge stability of the electrode are observed at a lower (0.1 M) cation concentration. At high electrolyte concentrations, the intercalated cations are firmly trapped, as indicated by the structural modifications observed in Raman analysis, resulting in much less photocharging and discharging abilities in subsequent cycles. The study also shows that the stored electrons can be successfully used to generate H(2) with 100 % faradaic efficiency in the absence of light.