A Study on the Catalytic Activity and Service Lifetime of RuO₂‐TiO₂ Composite Electrode with TNTs as Interlayer

Abstract

Herein, we reported a novel RuO 2 -TiO 2 composite electrode prepared by thermal decomposition process using TiO 2 nanotube arrays (TNTs) as an interlayer. Specifically, the TNTs interlayer was fabricated by anodic oxidation on pure Ti plate, followed by heat-treatment (450°C) to transform its amorphous structure to anatase structure. This TNTs interlayer not only has a good protection for Ti substrate, but also has a low resistance. The resultant RuO 2 -TiO 2 electrode presents superior performance toward chlorine evolution reaction (ClER) and longer service lifetime (132 h) than that without interlayer (59 h). Experimental results show that anodizing time determines the length of TiO 2 nanotubes and brings about different catalytic activity and stability. The RuO 2 -TiO 2 /TNTs/Ti electrode with an optimal RuO 2 -TiO 2 coating (4.5 g m À 2 ) presents a better spatial structure, homogeneous crystal particles, uniformly distribution and more active sites. However, high calcination temperature (> 600°C) has a detrimental impact, i. e. the collapse of TNTs and a "cracked mud" structure, which provide a path for oxygen and electrolyte to penetrate into the substrate and cause the spalling of coating, eventually lead to a serious decline in electrocatalytic activity and stability.

Electrochemical Properties of Ti/SnO2-Sb-Ir Electrodes Doped with a Low Iridium Content for the Oxygen Evolution Reaction in an Acidic Environment

“…First, stabilizers such as Ta 2 O 5 or RuO 2 can be introduced to improve the electrode stability. Secondly, an intermediate layer can be added to inhibit the formation of the TiO 2 passivation layer. − …”

Review on Structural Adjustment Strategies of Titanium‐Based Metal Oxide Dimensionally Stable Anodes in Electrochemical Advanced Oxidation Technology

“…[66] Achieving high-efficiency and long-life electrodes remains a great challenge; 2) Titanium-based RuO 2 (Ti/RuO 2 ) has become a promising anode material recently for degrading organic pollutants due to its low cost, good dimensional stability, high efficiency under strongly acidic conditions, high activity for generating strong oxidizers (free radicals), and higher oxygen evolution potential (OEP) (1.9 V). [67][68][69][70] However, there are well-known disadvantages such as low service life and low specific surface area; [71,72] 3) Titanium-based PbO 2 (Ti/PbO 2 ) is obtained by electrodepositing a layer of PbO 2 on the Ti substrate. [73] In the traditional Ti/PbO 2 electrode, PbO 2 coating has poor adhesion, an unstable film, large interface resistance, and short life cycle, which are the major disadvantages of PbO 2 electrode; 4) SnO 2 electrode has the advantages of high OEP, low toxicity and corrosion resistance, and is an excellent electrode material.…”

“…• High efficiency under strongly acidic conditions • High chemical and mechanical resistant • High electrocatalytic activity for generation of strong oxidants (Cl⋅, ⋅OH, [67][68][69][70] • Low service life [71] • Low specific surface area [72] Ti/PbO 2 • Low cost and high electrical conductivity • High OEP (>1.8 V) [15] • Good corrosion resistance [185] and chemical inertness [186] • Poor performance in wastewaters comprising chlorides and inability to resist corrosion [68] • PbO 2 active layer of Ti/PbO 2 is easily exfoliated from the surface of the Ti substrate, especially in sulfuric acid systems, and lead leaching occurs, [69] which leads to poor stability and activity and short electrode life [185,186] Ti/Sb-SnO 2 • Low cost, toxicity, and corrosion resistance • High electrocatalytic activity [110] High OEP (>1.8 V) [187] • High resistivity and short service lifetime [187] Ti/TiO 2 • Good orientation, high mechanical strength, and large specific surface area [80] • Unique unidirectional electron pathway [129] • Semiconducting properties, the poor electrical conductivity [164] voltammetry (LSV) and cyclic voltammetry (CV) tests in Figure 2f,g show that Ti/Ta 2 O 5 -IrO 2 electrode had higher OEP and larger electrochemical effective surface area (consistent with the SEM image). Higher OEP was beneficial to inhibit the occurrence of side reactions and improve the degradation ability for organic matter.…”

“…The resulting RuO 2 -TiO 2 electrode exhibits excellent performance in chlorine evolution reaction and has a longer lifetime (132 h) than the electrode without the interlayer (59 h). [71] The combined anode of RuO 2 and carbon materials is feasible and promising for efficient electrochemical degradation of pollutants, such as RuO 2 -TiO 2 /nanographite composite anode with RuO 2 and TiO 2 nanoparticles uniformly distributed on the surface of nanographite sheet. The synergistic effect of RuO 2 , TiO 2 , and nanographite increases the specific surface area, improving the EO activity and reducing the charge [100] Copyright 2019, IOP.…”

“…TiO 2 NTAs can be used as an interlayer between the substrate and the mixed metal oxide coating to improve anode electrochemical behavior and life by retarding titanium passivation. [ 71 ] When RuO 2 nanoparticles (size < 10 nm) were deposited on the inner and outer surfaces of TiO 2 NTAs without blocking the tubes and with uniform distribution of Ru, as shown in Figure a–c, the composite electrode showed a very high surface area. It has been used to efficiently degrade refractory compounds, as shown in Figure 4d.…”