•The Nickel-phosphate decorated phosphate-Fe2O3 photoanode (NiPi/Pi-Fe2O3) was fabricated.•NiPi/Pi-Fe2O3 showed enhanced photoelectrochemical activity of glycerol oxidation.•The NiPi/Pi-Fe2O3-based photoelectrochemical (PEC) glycerol fuel cell works efficiently and stably in neutral electrolyte.•The C-C bond in glycerol could be efficiently cleaved in PEC glycerol fuel cell.The nickel-phosphate decorated phosphate-Fe2O3 photoanode (NiPi/Pi-Fe2O3) was fabricated by coating phosphate modified hematite (Pi-Fe2O3) with naturally abundant nickel-phosphate complexes (NiPi). X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy studies showed that NiPi was uniformly distributed on Pi-Fe2O3 surface as amorphous form. With the decoration of NiPi, the photocurrent of Pi-Fe2O3 was enhanced by ca. 2 times at 1.5 V (vs. RHE). The NiPi/Pi-Fe2O3 also exhibited higher maximum power generation in photoelectrochemical (PEC) glycerol-based fuel cell, which was ca. 2.4 times than that of Pi-Fe2O3. Electrochemical impedance spectroscopy analysis revealed the charge transfer resistance at the interface of Pi-Fe2O3/electrolyte was remarkably decreased by NiPi decoration. NiPi was believed to be not only a hole-conductor that promoting the charge separation but also a catalyst for glycerol oxidation through cyclic changes between the lower and the higher oxidation states of Ni, which were the main reasons for the enhanced PEC response and power generation. The intermediates from glycerol were verified using high performance liquid chromatography, indicating the efficient cleavage of C-C bonds in glycerol on NiPi/Pi-Fe2O3. This work demonstrates NiPi/Pi-Fe2O3 has great potential in PEC fuel cells for the generation of electricity from light energy and biomass energy.Enhanced photoelectrochemical activity of Nickel-phosphate decorated phosphate-Fe2O3 photoanode for glycerol-based fuel cell.Download high-res image (207KB)Download full-size image

As a promising photoanode material, hematite (α-Fe2O3) can be used for photoelectrochemical (PEC) water oxidation but there are still great challenges, such as low efficiency and poor stability in neutral pH electrolyte, before it can be used in practice. Herein, a CoAl layered double hydroxide (CoAl-LDH) has been deposited in situ onto α-Fe2O3 nanoarrays. The PEC performances of the resulting composite photoanodes (CoAl-LDH/α-Fe2O3) towards water oxidation were investigated in neutral pH electrolyte. Contrastive experiments indicated that Co2+ in CoAl-LDH provided active catalytic sites for water oxidation, while Al3+ was inactive and offered support for the layered skeleton. CoAl-LDH could have a dual role as an efficient cocatalyst to lower the onset potential and enhance the photocurrent of α-Fe2O3, and as an effective protector of α-Fe2O3 from corrosion in neutral pH electrolyte. Relative to that of bare α-Fe2O3, a ∼250 mV negatively shifted onset potential and an almost 9-fold enhancement in photocurrent density at 1.23 V vs. RHE were observed with CoAl-LDH/α-Fe2O3. Moreover, CoAl-LDH/α-Fe2O3 showed excellent stability at 1.23 V vs. RHE with a steady photocurrent of ∼2 mA cm−2 even after 2 h of irradiation, which was very close to 100% of the initial value. Electrochemical impedance spectroscopy analysis revealed that the charge transfer resistance at the interface of α-Fe2O3/electrolyte was significantly decreased by CoAl-LDH decoration. Using H2O2 as a hole scavenger, the charge injection efficiency at the interface of CoAl-LDH/α-Fe2O3 and electrolyte was recorded as 84% at 1.23 V vs. RHE, which was 4-fold higher than that at the interface of α-Fe2O3 and electrolyte. This work demonstrates that CoAl-LDH decorated semiconductors have great potential as efficient and stable photoanodes towards high PEC performance in neutral pH electrolyte.

As a promising photoanode material, hematite (α-Fe2O3) can be used for photoelectrochemical (PEC) water oxidation but there are still great challenges, such as low efficiency and poor stability in neutral pH electrolyte, before it can be used in practice. Herein, a CoAl layered double hydroxide (CoAl-LDH) has been deposited in situ onto α-Fe2O3 nanoarrays. The PEC performances of the resulting composite photoanodes (CoAl-LDH/α-Fe2O3) towards water oxidation were investigated in neutral pH electrolyte. Contrastive experiments indicated that Co2+ in CoAl-LDH provided active catalytic sites for water oxidation, while Al3+ was inactive and offered support for the layered skeleton. CoAl-LDH could have a dual role as an efficient cocatalyst to lower the onset potential and enhance the photocurrent of α-Fe2O3, and as an effective protector of α-Fe2O3 from corrosion in neutral pH electrolyte. Relative to that of bare α-Fe2O3, a ∼250 mV negatively shifted onset potential and an almost 9-fold enhancement in photocurrent density at 1.23 V vs. RHE were observed with CoAl-LDH/α-Fe2O3. Moreover, CoAl-LDH/α-Fe2O3 showed excellent stability at 1.23 V vs. RHE with a steady photocurrent of ∼2 mA cm−2 even after 2 h of irradiation, which was very close to 100% of the initial value. Electrochemical impedance spectroscopy analysis revealed that the charge transfer resistance at the interface of α-Fe2O3/electrolyte was significantly decreased by CoAl-LDH decoration. Using H2O2 as a hole scavenger, the charge injection efficiency at the interface of CoAl-LDH/α-Fe2O3 and electrolyte was recorded as 84% at 1.23 V vs. RHE, which was 4-fold higher than that at the interface of α-Fe2O3 and electrolyte. This work demonstrates that CoAl-LDH decorated semiconductors have great potential as efficient and stable photoanodes towards high PEC performance in neutral pH electrolyte.

•The photocatalytic performance of Ag3PO4 was enhanced by a facile high temperature calcination method.•The crystallinity and oxygen defects of Ag3PO4 increase with the increasing calcination temperature.•Ag3PO4 calcined at 400 °C displays superior photocatalytic activity.•The crystallinity, oxygen defects and surface area play vital roles on the photocatalytic performance.In this work, Ag3PO4 photocatalysts were prepared via coprecipitation method followed by high temperature calcination. The physicochemical properties of received Ag3PO4 photocatalysts were systematically investigated by using X-ray diffraction, ultraviolet–visible diffuse reflection spectroscopy, scanning electron microscopy, transmission electron microscopy, specific surface area, X-ray photoelectron spectroscopy and electrochemical measurements. The high temperature calcination induces the improvement of crystallinity, the increase of oxygen vacancies, and the decrease of specific surface area of Ag3PO4. The activities of Ag3PO4 towards photocatalytic oxygen evolution and Methylene blue degeneration were found to be highly dependent on the calcination temperature. The Ag3PO4 annealed at 400 °C exhibits the highest photocatalytic oxygen evolution of 87.6 μmol g−1 h−1, which is ca. 4 times higher than that of Ag3PO4 obtained by coprecipitation method. Moreover, the Ag3PO4 annealed at 400 °C demonstrated the best photocatalytic degeneration of Methylene blue (MB) under visible light. The variation of physicochemical properties including crystallinity, oxygen vacancies and specific surface area of Ag3PO4 should be responsible for the enhanced photocatalytic activities. The present work opens an avenue to construct efficient Ag3PO4-based photocatalysts by high temperature calcination.

•Ag3PO4-photocatalytic degradation of MB is highly affected by metal cations.•The concentrations of metal cations strongly affect the adsorption and degradation.•Deactivation of Ag3PO4 is related to the adsorption and ion-exchange of metal cations.•The practical photocatalytic decontamination with Ag3PO4 needs prevent cations from waters.Metal cations existing invariably in natural and waste waters play crucial roles on the degradation efficiency of photocatalysts. Herein, the photocatalytic degradation of methylene blue (MB) on Ag3PO4 in the presence of metal cations (Na+, K+, Mg2+, Ca2+, Zn2+, Mn2+, Cu2+, and Fe3+) was investigated. It was found that the adsorption and the degradation rate of MB on Ag3PO4 are very sensitive to the interfering cations except Na+ and K+. In general, the adsorption and the degradation rate of MB could be strongly inhibited by Zn2+, Mn2+, and Cu2+ even at a low concentration of 0.1 mmol L−1, while Mg2+ and Ca2+ show slight suppressing effects. Fe3+ exhibits a unique effect, that is, under low concentration of 0.02–0.1 mmol L−1, Fe3+ demonstrates slight enhancement on the adsorption and the degradation of MB, whereas Fe3+ with high concentration of >0.1 mmol L−1 causes detrimental effect. Inductively coupled plasma-atomic emission spectrometer and transmission electron microscopy results suggest that the strong adsorption and ionic-exchange of metal cations are the main factors to the inhibited performance of Ag3PO4. The work presents great importance on the practical application of Ag3PO4 for photocatalytic water decontamination; namely, the waters should be pretreated to remove such cations before photocatalytic decontamination.Download high-res image (98KB)Download full-size image

As a promising photoanode material, hematite (α-Fe2O3) can be used for photoelectrochemical (PEC) water oxidation but there are still great challenges, such as low efficiency and poor stability in neutral pH electrolyte, before it can be used in practice. Herein, a CoAl layered double hydroxide (CoAl-LDH) has been deposited in situ onto α-Fe2O3 nanoarrays. The PEC performances of the resulting composite photoanodes (CoAl-LDH/α-Fe2O3) towards water oxidation were investigated in neutral pH electrolyte. Contrastive experiments indicated that Co2+ in CoAl-LDH provided active catalytic sites for water oxidation, while Al3+ was inactive and offered support for the layered skeleton. CoAl-LDH could have a dual role as an efficient cocatalyst to lower the onset potential and enhance the photocurrent of α-Fe2O3, and as an effective protector of α-Fe2O3 from corrosion in neutral pH electrolyte. Relative to that of bare α-Fe2O3, a ∼250 mV negatively shifted onset potential and an almost 9-fold enhancement in photocurrent density at 1.23 V vs. RHE were observed with CoAl-LDH/α-Fe2O3. Moreover, CoAl-LDH/α-Fe2O3 showed excellent stability at 1.23 V vs. RHE with a steady photocurrent of ∼2 mA cm−2 even after 2 h of irradiation, which was very close to 100% of the initial value. Electrochemical impedance spectroscopy analysis revealed that the charge transfer resistance at the interface of α-Fe2O3/electrolyte was significantly decreased by CoAl-LDH decoration. Using H2O2 as a hole scavenger, the charge injection efficiency at the interface of CoAl-LDH/α-Fe2O3 and electrolyte was recorded as 84% at 1.23 V vs. RHE, which was 4-fold higher than that at the interface of α-Fe2O3 and electrolyte. This work demonstrates that CoAl-LDH decorated semiconductors have great potential as efficient and stable photoanodes towards high PEC performance in neutral pH electrolyte.

As a promising photoanode material, hematite (α-Fe2O3) can be used for photoelectrochemical (PEC) water oxidation but there are still great challenges, such as low efficiency and poor stability in neutral pH electrolyte, before it can be used in practice. Herein, a CoAl layered double hydroxide (CoAl-LDH) has been deposited in situ onto α-Fe2O3 nanoarrays. The PEC performances of the resulting composite photoanodes (CoAl-LDH/α-Fe2O3) towards water oxidation were investigated in neutral pH electrolyte. Contrastive experiments indicated that Co2+ in CoAl-LDH provided active catalytic sites for water oxidation, while Al3+ was inactive and offered support for the layered skeleton. CoAl-LDH could have a dual role as an efficient cocatalyst to lower the onset potential and enhance the photocurrent of α-Fe2O3, and as an effective protector of α-Fe2O3 from corrosion in neutral pH electrolyte. Relative to that of bare α-Fe2O3, a ∼250 mV negatively shifted onset potential and an almost 9-fold enhancement in photocurrent density at 1.23 V vs. RHE were observed with CoAl-LDH/α-Fe2O3. Moreover, CoAl-LDH/α-Fe2O3 showed excellent stability at 1.23 V vs. RHE with a steady photocurrent of ∼2 mA cm−2 even after 2 h of irradiation, which was very close to 100% of the initial value. Electrochemical impedance spectroscopy analysis revealed that the charge transfer resistance at the interface of α-Fe2O3/electrolyte was significantly decreased by CoAl-LDH decoration. Using H2O2 as a hole scavenger, the charge injection efficiency at the interface of CoAl-LDH/α-Fe2O3 and electrolyte was recorded as 84% at 1.23 V vs. RHE, which was 4-fold higher than that at the interface of α-Fe2O3 and electrolyte. This work demonstrates that CoAl-LDH decorated semiconductors have great potential as efficient and stable photoanodes towards high PEC performance in neutral pH electrolyte.