Pb Cathode Research Articles

Enhanced Oxalic Acid Electroreduction Selectivity toward Glyoxylic Acid on Ti3+‐Self‐Doped TiO2 Nanotube Arrays

AbstractElectroreduction of oxalic acid (OX) to glyoxylic acid (GO) is an extremely important and promising application in organic electrosynthesis. Pb cathodes, which exhibits good selectivity, need to be replace due to the severe deactivation and harmful to the environment. Herein, self‐doped titanium dioxide nanotube arrays (H‐TiO2NTs‐2) are synthesized as an alternative cathode for OX electroreduction to GO. Benefiting from two‐step anodization, the synthesized nanotube arrays are highly ordered with oriented openings. The ordered structure promotes the mass transfer of both OX and GO to ensure efficiently providing OX reactants for the diffusion‐controlled OX electroreduction and removal of GO products from the electrode to prevent the over‐reduction to glycolic acid. Additionally, the electroreduction treatment introduces more Ti3+ active sites and modulates the conduction band position of H‐TiO2NTs‐2, thereby enhancing the reduction driving force. Owing to the unique structural advantages, the Faraday efficiency of generating GO from OX reaches up to 81.3 % in an oxalic acid saturated electrolyte at 20 °C with a current density of 1500 A m−2. This designed H‐TiO2NTs‐2 holds broad application prospects in OX electroreduction.

Enhanced Electrohydrogenation of Cis,Cis-Muconic Acid to Trans-3-Hexenedioic Acid Using Hybrid Metal/Carbon Fiber Cathodes

Organic electrosynthesis is a long-known technique for diverse product development and efficient synthesis. With the recent rise of biomass as an alternative carbon and energy source, electrochemistry is further gaining popularity due to its inherently green and environmentally benign operating conditions. Electrochemical hydrogenation (ECH) reactions are particularly attractive for biomass conversion due to their ability to abstract hydrogen from water, tolerate biogenic impurities, and utilize Earth-abundant base metal electrodes. Moreover, the rate and selectivity of the reaction can be tubed by controlling the electrode material, operating potential/current density, and reactor design. However, the implementation of this decarbonized technology for chemical production is still hampered by low productivity and, as a result, unfavorable economics. cis,cis-Muconic acid (ccMA), a bioderived C6 diunsaturated diacid platform molecule, can be converted into commodity chemicals like caprolactam, adipic acid (AA), and terephthalic acid, with AA being of particular interest for the synthesis of nylon 6,6.1 Apart from various drop-in chemicals, ccMA can also be electrochemically upgraded to trans-3-hexenedioic acid (t3HDA), a potential bio-advantaged substitute for AA as the additional C=C bond in t3HDA can be leveraged to synthesize performance-advantaged polyamides.2,3 In this work, we investigated the electrohydrogenation of ccMA to t3HDA over Pb cathodes. We demonstrate that the reaction follows a radical-based pathway involving sequential electron transfer and hydrogen addition in solution to selectively produce t3HDA (100% selectivity). Next, we contacted the cathode with carbon felts (CF) to increase productivity. CF are often used in fuel cells and H2O2 electrolyzers due to their excellent conductivity, porosity for enhanced turbulence, and ability to tune the gas-liquid-solid three-phase interface. Following similar principles, we placed a CF (3mm. thickness) in contact with the Pb cathode to lower the charge transfer resistance (~3Ω) at the interface. The surface functionalities of carbon allowed us to further tune the hydrophobicity/hydrophilicity of our hybrid electrode. Molecular dynamics (MD) calculations provided critical insights into the role of surface functionalities and guided the optimal functionalization of CF’s surface. Combining reactor configuration with fine-tuning of the electrode’s microenvironment, we were able to achieve a 50x increase in t3HDA productivity reaching up to 20 g/cm2/day at a current density of 200 mA/cm2. We further replaced the kinetically sluggish oxygen-evolution reaction with the glucose oxidation reaction at the anode, allowing us to operate the electrolyzer at a lower cell potential.Overall, ECH represents a valuable alternative to thermochemical transformations for biomass upgrading. This work provides critical insights into reactor modifications for the scaled-up synthesis of bio-derived performance monomers via hybrid microbial electrosynthesis (HMES).

Copper, Zinc, and Lead Recovery from Jarosite Pb–Ag Tailings Waste (Part 2)

The present paper describes the technological solution for obtaining Cu, Zn, Pb, and Ag from jarosite waste raw material, with its simultaneous separation from In and Fe. By roasting at low temperatures, iron was transformed from the Fe2(SO4)3 form into Fe2O3, which is insoluble in water and slightly soluble in acid. Copper sulfate and zinc sulfate are present in jarosite as sulfates. During temperature roasting, the copper and zinc were still in the form of CuSO4 and ZnSO4, i.e., they were easily dissolved in water. This procedure led to good selectivity of Cu and Zn compared to Fe. After water leaching, PbSO4 and Ag2SO4 remained in the solid residue. By treating jarosite with a content of 0.7% Cu, 5.39% Zn, and 5.68% Pb, products of commercial quality were obtained. By roasting jarosite in an electric furnace and leaching the roasted sample in water, leaching degrees of 91.07%, 91.97%, and 9.60% were obtained for Cu, Zn, and Fe, respectively. Using 1 M NaOH in the leaching solution, 99.93% Fe was precipitated to pH = 4. Cu in the form of CuSO4 was further treated by cementation with Zn, after which cement copper was obtained as a commercial product. Zn in the form of ZnSO4 was further treated by precipitation with Na2CO3 to obtain ZnCO3 concentrate of commercial grade. The total recovery of Pb and Ag, which were treated by chloride leaching, was 96.05% and 87.5%, respectively. The resulting NaPbCl3 solution was further treated with Na2CO3 solution, whereby PbCO3 was obtained as a commercial product. The produced PbCO3 could be further subjected to roasting to obtain soluble PbO. In these investigations, PbCO3 was smelted where a Pb anode was obtained; this was electrolytically refined to a Pb cathode. The proposed process does not pollute the environment with As and Cd.

Preparation of Pb-Ca Master Alloy by Molten Salt Electrolysis

Lead-acid batteries (LABs) are commonly utilized in various applications such as electric motorcycles, uninterruptible power systems, and stationary energy storage devices. Calcium (Ca) is an essential element being added to Pb grid alloys to increase their mechanical strength. In this paper, molten salt electrolysis is used to prepare Pb-Ca master alloy in molten CaCl2-NaCl at 700 °C. The Ca concentration reaches 2.51 wt%, and the current efficiency reaches 85.0% for the 1 A-scale electrolyzer and 75.8% for the 50 A-scale cell. Compared with the traditional physical mixing ways, Ca is selectively and gradually deposited in the liquid Pb cathode without worrying about the immense heat generated by mixing Ca and Pb. In addition, molten salt serves as a media to avoid the oxidation of Ca. Through thermodynamic calculations and electrochemical measurements, the Pb-Ca formation prefers to happen rather than Pb-Na alloy in molten CaCl2-NaCl because of the stronger interaction of Ca and Pb than Na and Pb. Overall, this paper provides a straightforward strategy to prepare Pb-Ca master alloys, which can be expanded to prepare various liquid semimetal alloys containing reactive metals.

Study of the Structure and Mechanisms of Wear of Solid-Lubricant Coatings of the TiN–Pb System

Сomposite solid lubricating coatings TiN–Pb with a thickness of ~2 μm were produced by co-sputtering of Ti and Pb cathodes of two separate magnetrons on titanium alloy VT6. The Pb content in the coating averages ~12 at. %. The inner layer is coating characterized by a uniform distribution of Pb, and the upper layer is characterized by the presence of islands with a high content of Pb. The coating structure is globular, predominantly containing nanometer-sized crystallites. The absence of a columnar structure of the coating is associated with a high content of Pb, which is insoluble in the TiN matrix and interrupts the growth of crystallites. X-ray diffraction analysis showed the presence of Pb, PbO, and TiN phases in the coatings. The diffraction lines are broadened, which indicates that the crystallite size is ~10–20 nm in the coating. Tribological tests of the TiN–Pb coating were carried out under conditions of low-amplitude friction – fretting wear in a wide range of loading parameters. In the full slip mode, a friction coefficient of ~0.25 is observed. During the transition from the full slip mode to the reciprocating slip mode, the energy dissipated during friction drops by more than three times, which is also reflected in a sharp decrease in the friction coefficient from 0.25 to 0.05.

Initiation of Artificial Radioactivity of Impurity Elements in a Lead Cathode under Conditions of a Glow Discharge

The possibility of initiation of nuclear chemical processes in the Pb cathode during a glow discharge in a low-temperature deuterium-containing nonequilibrium plasma leading to a significant (at times) decrease in the isotope content of some impurity elements (specifically, Zn) and increasing others (specifically, W, Fe, Mn, and Al). Such processes can be understood by introducing the existence in nuclear matter of metastable non-nucleon excitations of internal shaking (isu-states) formed by initiating actions on the nuclei of electrons with high (on chemical scales) kinetic energy Ee ~ 3–5 eV.

Prolonged Stability of Pb-Catalyzed CO2 Electroreduction to Methyl Formate in Acidic Methanol

Electrochemical CO2 reduction from renewable energy is a promising route to mitigate greenhouse gas emissions from waste sources while generating value-added products. CO2 electroreduction in methanol is particularly interesting due to the increased CO2 solubility compared to water and the propensity to form methyl formate, a product absent in aqueous electrolysis. Four factors have been identified as critical to achieving prolonged high selectivity for methyl formate production on a Pb cathode in methanol: high pH near the electrode, low bulk pH, low water content, and regeneration of Pb2+ sites. Increasing concentration of the formic acid product was observed to induce a selectivity shift toward hydrogen, which was mitigated by the in situ conversion of the formic acid to methyl formate via an esterification reaction. Furthermore, co-electrolysis of CO2 with dilute molecular oxygen (4% O2) led to Pb catalyst repair through in situ surface oxidation. Using CO2 and dilute O2 along with single-pass catholyte flow to maintain a low formic acid concentration, sustained high selectivity for methyl formate was attained at ∼60% faradaic efficiency at −20 mA cm–2 for over 72 h.

Sensitive and Environmentally Friendly Field Analysis of Waterborne Arsenic by Electrochemical Hydride Generation Microplasma Optical Emission Spectrometry.

To avoid polluting the environment, it is desirable to develop methods consuming as few chemicals as possible for field elemental analysis. In this work, a lithium-ion battery supplied, compact handheld optical emission spectrometer (OES) (0.3 kg, length 18 cm × width 5 cm × height 10 cm) was fabricated for the sensitive field analysis of waterborne arsenic by utilizing electrochemical hydride generation (ECHG) and miniaturized ballpoint discharge (μPD) as sample introduction means and excitation source, respectively. The high ECHG efficiency of arsenic was obtained using a superior cathode of Fe@PbO/Pb and the generated arsine was separated from an aqueous phase and further swept to the μPD microplasma for detection. It is worth noting that the Fe@PbO/Pb cathode not only retains advantages of large specific surface area, robust stability, and excellent reproducibility for the ECHG of arsenic but also accomplishes the preconcentration of As(III), thus improving the kinetics of the surface chemistry at the cathode, alleviating the corrosion of the electrode, and minimizing the release of Pb. A limit of detection of 1.0 μg L-1 was obtained with a relative standard deviation of 4.2% for 20 μg L-1 As(III). Owing to the advantages of ECHG and μPD-OES, the system retains a promising potential for the sensitive, cost-effective, and environmentally friendly field analysis of waterborne arsenic.

High-performance Ni/Fe-codoped manganese hexacyanoferrate by scale-up synthesis for practical Na-ion batteries

Manganese hexacyanoferrate Prussian blue (Mn−PB) is regarded as promising cathode for sodium-ion batteries (SIBs) because of high energy density, low cost and facile preparation route. However, poor rate capability and short cycle life restrain practical applications of Mn−PB. In this work, a Na-rich Mn-based Prussian blue with codoped Ni and Fe (MnFeNi-PB) was prepared via a citrate sodium-assisted coprecipitation route. The Ni/Fe codoping significantly increases rate capability and cycling performance of the Mn−PB. Even at 100 C, the MnFeNi−PB exhibits a high capacity of 84.0 mAh g−1, with 72.8% capacity delivered relative to 0.1 C. The material also shows stable cycling with 65.6% capacity retained after 2000 cycles at a current density up to 5 C. Even under stringent circumstances, the MnFeNi−PB also exhibits a high capacity retention of 83.5% after 300 cycles at 45 °C and 92.1% after 700 cycles at −20 °C at 1 C. The enhanced rate capability and cycling performance is attributed to the increased electronic conductivity and stabilized crystal structure by Ni/Fe codoping. Scalable preparation of kilogram-grade MnFeNi−PB was realized using a 100 L reactor. Pouch-type Na-ion full battery with the MnFeNi−PB cathode shows stable cycling with 84.9% capacity retained after 200 cycles at 0.5 C/1 C current rate.

Pb cathode assisted electrochemical extraction of Pr(III) by formation of Pb3Pr in LiCl–KCl melts

Pb cathode assisted electrochemical extraction of Pr(III) by formation of Pb3Pr in LiCl–KCl melts

Electrochemical separation of La from LiCl-KCl fused salt by forming La-Pb alloys

To separate La from LiCl-KCl fused salt by forming La-Pb alloy, the electrochemical codeposition of Pb(II) and La(III) on inert W electrode and electroreduction of La(III) on liquid Pb were explored, respectively, using a group of electrochemical measurement methods. The formation mechanism reduction peak potentials of La-Pb intermetallics were obtained from the results of cycle voltammetry (CV), square wave voltammetry (SWV) and anodic stripping voltammetry (ASV). The kinetic data of La(III)/La (in Pb) couple on liquid Pb cathode, for instance, exchange current density, transfer coefficient, charge transfer resistance and activation energy, were studied by linear polarization and Tafel techniques. Moreover, constant potentials electrolysis (CPE) and constant current electrolysis (CCE) were conducted onliquid Pb cathode to recover La from fused salt. The electrolytic products checked by SEM-EDS and XRD were composed of LaPb3 phases.The maximum separation efficiency of La could reach 92.03% after CCE (0.15 A) for 7 h, which confirmed the feasibility of separating La from LiCl-KCl fused salt.

Structure and properties of TiN–Pb composite coatings deposited on VT6 alloy by DC magnetron sputtering

DC reactive magnetron sputtering of two separate single-element Ti and Pb targets was used to deposit a TiN–Pb composite coating onto a substrate made of the VT6 titanium alloy. The studies were carried out at Pb cathode currents of 0.2 and 0.1 A and two fixed argon flow rate values of 6.0 or 8.5 cm3/min, and the flow rate of nitrogen supplied to the chamber varying from experiment to experiment. The composition of coatings was determined by energy dispersive analysis. It was shown that the amount of lead in the coatings ranged from 0.5 to 16 wt.% depending on the Pb cathode current and reactive nitrogen consumption. Coating microhardness and wear were determined for each deposition mode. It was found that coating thicknesses varied from 1.9 to 5.2 μm depending on the ratio of argon and nitrogen fluxes. The effect of TiN–Pb magnetron coating deposition parameters on the structure and phase composition was investigated by X-ray diffraction method. It was shown that the coating consists of Pb and PbO at the Pb cathode current of 0.2 A, and of TiN, Pb, and PbO at the current of 0.1 A, while an increase in the ratio of argon and nitrogen fluxes leads to an increase in the fraction of TiN, the intensity of titanium substrate surface saturation with nitrogen, as well as microhardness and wear resistance. Under all deposition conditions the TiN coating features by a typical texture (111), the intensity of which varies nonmonotonically.

Influence of magnetron spraying parameters on the structure of TiN-Pb coatings

Using X-ray diffraction analysis, we studied the effect of a number of deposition parameters of magnetron TiN-Pb coatings on substrates made of 30KhGSA and 12Kh18N10T steels on the structure of the coatings. It is shown that at a current value of 0.1 A on the Pb cathode, the coating consists mainly of TiN with a pronounced (111) texture. An increase in the current at the Pb cathode to 0.2 A leads to the dominance of Pb and PbO in the coating structure. The influence of ion-assisted and nitrogen consumption on the structure of coatings is noted.

Study of the influence of the substrate material on the phase composition and thickness of Ti-Pb coatings deposited by a magnetron

The structure of coatings deposited by reactive magnetron sputtering of Ti and Pb cathodes on substrates from Mo, 30HGSA and 304 steel was studied by X-ray diffraction. The thickness of the coatings was determined by the difference between the CTE of the coating and the substrate, which is maximum for Mo coating and minimum for 304 steel, for which the thickest coating was found, consisting of tetragonal modifications of PbO.

Electrochemical recovery of dysprosium from LiCl-KCl melt aided by liquid Pb metal

To recover Dy from LiCl-KCl melt, the electroreduction mechanism of Dy(III) on liquid Pb electrode was first studied by CV and Tafel methods. Dy(III) was reducted on liquid Pb electrode at about −1.35 V which is more positive than that on W electrode due to the formation of Dy(Pb) solid solution: Dy(III) + Pb + 3e− = Dy(Pb). Tafel method was used to evaluate the exchange current density (j0) and charge transfer coefficient (α) of Dy(III)/Dy(Pb) couple on liquid Pb electrode, the influence of different scanning speeds and temperatures on j0 were studied. The linear dependence of j0 as a function of temperature was observed, from which the activation energy associated with Dy(III)/Dy(Pb) couple was also obtained. Then, the reduction process of Dy(III) on the Pb film coated on the W electrode was also performed to obtain more information of the Pb-Dy intermetallic compounds. Electrochemical signals associated with the formation of Pb3Dy, Pb2Dy, Pb4/5Dy and Pb3/5Dy, were observed. The deposition potentials and equilibrium potentials of different Pb-Dy intermetallic compounds were obtained, which are more positive than those of Dy(III) on W electrode. Thermodynamic properties of Pb-Dy intermetallic compounds at 713 K–803 K were calculated employing the determined equilibrium potentials. The metallic Dy was recovered through galvanostatic and potentiostatic electrolysis on liquid Pb cathode and the products were detected by SEM-EDS and XRD. The recovered Dy was found to be in the form of Pb3Dy intermetallic compound.

A low-defect and Na-enriched Prussian blue lattice with ultralong cycle life for sodium-ion battery cathode

Prussian blue compounds have been considered as attractive candidate cathodes for sodium ion battery (SIB) due to open channel structure, tunable chemical compositions and potential high capacity. However, their low capacity utilization and insufficient cyclability have hindered their large-scale applications. In this work, a series of Na-enrich PB lattices (NaxFe[Fe(CN)6]1-y · zH2O) with different contents of [Fe(CN)6] vacancies and coordinated water are synthesized to investigate the effects of the lattice defects on the reversible capacities and cycling stabilities of the PB materials. It is found that decreasing the content of structural defects can greatly elevate the electrochemical performance of the PB cathodes. The as prepared low-defect and Na+-enriched Na1.81Fe[Fe(CN)6]0.83 · 2.04H2O lattice can achieve a high reversible capacity of >140 mAh g−1, a superior rate capability with 55.2% of its initial capacity at 10 C and a long-term cyclability with 78% capacity retention over 3700 cycles, possibly serving as a low cost, high capacity and cycle-stable cathode for Na ion batteries.

Cathode Material Determines Product Selectivity for Electrochemical C−H Functionalization of Biaryl Ketoximes

AbstractThe synthesis of polycyclic N‐heteroaromatic compounds and their corresponding N‐oxides has been developed through electrochemical C−H functionalization of biaryl ketoximes. The oxime substrates undergo dehydrogenative cyclization when a Pt cathode is used, resulting in unprecedented access to a wide range of N‐heteroaromatic N‐oxides. The products of the electrosynthesis are switched to the deoxygenated N‐heteroaromatics by employing a Pb cathode through sequential anode‐promoted dehydrogenative cyclization and cathodic cleavage of the N−O bond in the initially formed N‐oxide.

Cathode Material Determines Product Selectivity for Electrochemical C-H Functionalization of Biaryl Ketoximes.

The synthesis of polycyclic N-heteroaromatic compounds and their corresponding N-oxides has been developed through electrochemical C-H functionalization of biaryl ketoximes. The oxime substrates undergo dehydrogenative cyclization when a Pt cathode is used, resulting in unprecedented access to a wide range of N-heteroaromatic N-oxides. The products of the electrosynthesis are switched to the deoxygenated N-heteroaromatics by employing a Pb cathode through sequential anode-promoted dehydrogenative cyclization and cathodic cleavage of the N-O bond in the initially formed N-oxide.

Photoelectrochemical Reduction of CO2 in Methanol with TiO2 Photoanode and Metal Cathode

This work focuses on the photoelectrochemical CO2 reduction at TiO2 photoanode and metal cathode in methanol-based electrolyte. The TiO2 nanotube photoanodes were obtained by anodization of Ti plate (30 × 20 mm) and calcination. The emphasis is placed on evaluating and comparing the current density and Faradaic efficiencies at different calcination temperatures, calcination times and cathodes (Pb and Ag). A result for calcination condition suggested that the optimum program of TiO2 photoelectrode was the calcination at 700 oC during 2 hours. The formation of carbon monoxide and methyl formate was monitored during UV radiation (365 nm) at an applied potential of 2.0 V vs. Ag QRE. The main product by photoelectrochemical reduction of CO2 with Pb cathode was methyl formate whereas it with Ag cathode was carbon monoxide.

Conversion of CO2 in Methanol into HCOOCH3 and CO By Photoelectrochemical Reduction with TiO2 Photoanode

Introduction Carbon dioxide is a linear and very stable molecule in which the oxygen atoms are weak Lewis (and Brønsted) bases and the carbon is electrophilicCarbon dioxide (CO2) is one of the main contributors to the global warming. Consequently, the conversion of CO2 into value-added products and/or high-energy content fuel will become one of the goals in environmental research. Among the various possible approaches, the photoelectrochemical reduction technique is used to reduce the CO2. It has been found that the electrochemical technique may not only convert CO2 from the environment but also the products by photoelectrochemical reduction of CO2 may be used as renewable energy. Methanol is better solvent of CO2 than water, particularly at a low temperature. Literature data for the solubility of CO2 in pure methanol and water, at 15 oC, were of 4.6 and 1.07 cm3 cm-3, respectively. Therefore, methanol has been used as a physical absorbent of CO2. In the present study, we investigated the performance of TiO2 nanotube prepared by anodization for the photoelectrochemical reduction of CO2 in the methanol. Also, the emphasis is placed on evaluating and comparing the current density and Faradaic efficiencies at different calcination temperatures, calcination times and different cathodes (Pb and Ag). Experimental The TiO2 photoanode was prepared by anodization Ti plate (30 × 20 mm) in hydrogen fluoride solution (1% in 10% CH3OH + 90% water) under ultrasound and calcination at 300-900 oC for improvement crystallinity of TiO2. The electrochemical reactor was operated using a potentiostat (HA-3001A) under ambient pressure and temperature. The 3.0 M KHCO3 and 0.3 M KOH in CH3OH solution was used as catholyte and anolyte, respectively, in a standard three-electrode H-type cell equipped with cathodes (Pb and Ag) as the counter electrode and a Ag/AgCl as reference electrode. Then, CO2 gas was bubbled into the methanol catholyte for 2 hours. Aldrich Nafion 117 ion exchange membrane was used as the diaphragm between photoanode and cathode. The working electrode (TiO2 photoelectrode) was irradiated by a UV light (365nm) for the photoelectrochemical reduction of CO2 in the methanol. The gaseous products obtained during electroreduction were collected in a gas collector and were analyzed by gas chromatography. Products soluble in the catholyte were analyzed by using high performance liquid chromatography. A scanning electron microscope (SEM) was used to characterize TiO2 electrode. Results and discussion As a result of the observation of TiO2 photoelectrode (calcination at 700 oC for 2 hours) before and after the photoelectrochemical reduction use with a scanning electron microscope (SEM), the electrode surface became a nanotube. TiO2 photoelecrode after the photoelectrochemical reduction had the broken part, but we were able to confirm a nanotube in a considerable part. To examine the electrochemical behavior with the photoelectrode, the photoreaction of TiO2 photoelectrode (calcination at 700 oC for 2 hours) with Pb and Ag cathode is observed at an applied potential of 2.0 V vs. Ag/AgCl for the anode. Because an electric current flowing at the potential (2.0 V vs. Ag/AgCl) under the illumination was different from that observed without the light with both Ag and Pb cathode, it was confirmed that the TiO2 photoelectrode could use the light energy. Also, because no remarkable changes of current density were observed for the Ag and Pb cathodes, the influence of metal materials on current density could not be observed. In order to identify the optimum program of calcination temperature and time, the photoelectrochemical reduction of CO2 was performed for evaluating and comparing the current density and Faradaic efficiencies at different calcination temperatures (300-900 oC) and calcination times (1-10 hours). A result for calcination temperature suggested that the current density and Faradaic efficiency for TiO2 photoelectrode at the 700 oC calcination for 2 hours with Pb cathode, at an applied potential of 2.0 V vs. Ag/AgCl, were J = 2.2 mA cm-2 and FE (HCOOCH3) = 107.6 %. Furthermore, a result for calcination time suggested that the current density and Faradaic efficiency for TiO2 photoanode at the calcination at 700 oC during 2 hours with Pb cathode, at an applied potential of 2.0 V vs. Ag/AgCl, were J = 2.1 mA cm-2 and FE (HCOOCH3) = 89.0%. The main product by photoelectrochemical reduction of CO2 with Pb cathode was HCOOCH3 whereas the main product with Ag cathode was CO. Consequently, the use of TiO2 photoanode may be possible for the application for the photoelectrochemical reduction of CO2, although further research is still required in order to develop highly active, selective and stable catalysts.