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Zinc oxide (ZnO) is a potential wide band gap semiconductor, but its high photoelectron-hole pairs recombination rate and poor light absorption ability limit its application to photoelectrochemical (PEC) water oxidation. To solve these problems, in this work, a reasonable band structure engineering was carried out on ZnO nanorod arrays (ZnO NRAs) with the co-decoration of nitrogen doped g-C3N4 (NCN) and carbon quantum dot (CQDs) solution. Narrow band gap NCN was loaded onto the surface of ZnO NRAs by a simple spin coating method, and then CQDs were modified on the ZnO/NCN NRAs. The composite photoanode of ZnO/NCN/CQDs NRAs was finally obtained. The PEC performance of the composite photoanode reaches 1.82 times that of the pristine ZnO photoanode, with a photocurrent density of up to 1.20 mA cm−2 at 1.23 V (vs. RHE) bias. The calculated value of ABPE for the composite photoanode was 0.258%, compared with 0.123% for the bare ZnO NRAs. The co-decoration of NCN and CQDs enhanced the charge separation efficiency and expanded the spectral response range, contributing to the improved PEC properties of the composite photoanode. [ABSTRACT FROM AUTHOR]

Two types of cobalt imidazole complexes, e.g. cobalt 2-methylimidazole (Co-MIm) and cobalt 1-ethylimidazole (Co-EIm), are adopted as surface passivation agents to modify the Sn-doped α-Fe2O3 nanorods (Sn-Fe2O3 NRs) photoanode by a facile impregnation method. Systematic characterizations are performed and the fabricated photoanodes are applied to photoelectrochemical (PEC) water oxidation. Interestingly, the cobalt imidazoles nanosheets are embedded into the Sn-Fe2O3 NRs film to form crack-like gaps and NRs bundles on the surface of the composite photoanodes, e.g. Co-MIm@Sn-Fe2O3 and Co-EIm@Sn-Fe2O3. With simulated sunlight irradiation and an applied potential of 1.23 V (vs. RHE), the photocurrent densities of the Co-EIm@Sn-Fe2O3 and Co-MIm@Sn-Fe2O3 reach 0.81 mA/cm2 and 0.61 mA/cm2 with enhanced stability, respectively, compared with 0.36 mA/cm2 of the Sn-Fe2O3. The gaps and bundles on the surface of the composite photoanodes make the surface rougher and improve their light absorption ability. Moreover, the cobalt imidazoles as passivation agents can effectively inhibit surface states from capturing charge carriers, reduce charge recombination and facilitate charge transfer, thus improving the PEC performance. Notably, it is found that the cobalt imidazole with a longer alkyl chain, e.g. Co-EIm, is more effective than the Co-MIm. [ABSTRACT FROM AUTHOR]

The WO3 is a promising photoanode material for photoelectrochemical (PEC) water oxidation. Loading co-catalysts is an effective strategy for favoring the charge transfer and light harvesting of WO3, which can in turn improve its PEC performance. Herein, the ferrihydrite (Fh), a kind of poorly crystalline iron oxide material, was loaded on the WO3 photoanode through a two-step hydrothermal synthesis. The obtained Fh/WO3 photoanode exhibited a remarkable photocurrent density of 0.6 mA/cm2 at 1.23 V (vs. RHE), which was 1.79 times higher than the bare WO3. For the Fh/WO3 photoanode, the bulk charge separation efficiency is 45.6% and the photoconversion efficiency is 0.066%, which are both higher than the bare WO3. The decorated Fh can form an additional interface between the WO3 and the electrolyte, which decreases the impedance and favors the charge transfer. Moreover, the Fh can function as a hole storage layer, which can temporarily store the photogenerated holes and induce the longer lifetime of charge carriers, thus improving the charge separation and water oxidation reaction kinetics. [ABSTRACT FROM AUTHOR]

The WO3 is a promising photoanode material for photoelectrochemical (PEC) water oxidation. Loading co-catalysts is an effective strategy for favoring the charge transfer and light harvesting of WO3, which can in turn improve its PEC performance. Herein, the ferrihydrite (Fh), a kind of poorly crystalline iron oxide material, was loaded on the WO3 photoanode through a two-step hydrothermal synthesis. The obtained Fh/WO3 photoanode exhibited a remarkable photocurrent density of 0.6 mA/cm2 at 1.23 V (vs. RHE), which was 1.79 times higher than the bare WO3. For the Fh/WO3 photoanode, the bulk charge separation efficiency is 45.6% and the photoconversion efficiency is 0.066%, which are both higher than the bare WO3. The decorated Fh can form an additional interface between the WO3 and the electrolyte, which decreases the impedance and favors the charge transfer. Moreover, the Fh can function as a hole storage layer, which can temporarily store the photogenerated holes and induce the longer lifetime of charge carriers, thus improving the charge separation and water oxidation reaction kinetics. [ABSTRACT FROM AUTHOR]