mV Decay Research Articles

Synergistically enhanced ORR and HER performance on Co-N-C coupled in-situ generated PtCo intermetallic

Integrating multi-scale sites in a composite catalyst is vital to realize efficient electrocatalysis. Herein, a synergistic composite catalyst consisting of Co atomic sites and in-situ generated PtCo intermetallic compounds (IMCs) (o-PtCo@CoNC) is proposed through Co pre-anchoring and subsequent impregnation-reduction method. High loading of Co atoms provides a chance for in-situ generating PtCo ordered intermetallic compounds. The remaining Co single atoms and PtCo IMCs construct synergistic electrocatalytic micro-regions. Benefiting from the ordered structure, synergistic effect of PtCo IMCs and Co single atoms, o-PtCo@CoNC exhibits excellent electrocatalytic performance for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) with mass activity of 1.21 A mgPt−1 (at 0.9 V) and 5.70 A mgPt−1 (at an overpotential of 100 mV), respectively. Besides, o-PtCo@CoNC delivers negligible loss of half-wave potential and overpotential during long-term stability test in acid solutions, with 13 mV decay after 50,000 potential cycles for ORR and a 2.7 mV decay after 20,000 potential cycles for HER. The integration strategy of single-atomic sites coupled IMCs paves the way for enhancing the activity and durability of Pt-based electrocatalysts.

Hydrogen Peroxide Spillover on Platinum-Iron Hybrid Electrocatalyst for Stable Oxygen Reduction.

Iron-nitrogen-carbon (Fe-N-C) catalysts, although the most active platinum-free option for the cathodic oxygen reduction reaction (ORR), suffer from poor durability due to the Fe leaching and consequent Fenton effect, limiting their practical application in low-temperature fuel cells. This work demonstrates an integrated catalyst of a platinum-iron (PtFe) alloy planted in an Fe-N-C matrix (PtFe/Fe-N-C) to address this challenge. This novel catalyst exhibits both high-efficiency activity and stability, as evidenced by its impressive half-wave potential (E1/2) of 0.93 V versus reversible hydrogen electrode (vs RHE) and minimal 7 mV decay even after 50,000 potential cycles. Remarkably, it exhibits a very low hydrogen peroxide (H2O2) yield (0.07%) at 0.6 V and maintains this performance with negligible change after 10,000 potential cycles. Fuel cells assembled with this cathode PtFe/Fe-N-C catalyst show exceptional durability, with only 8 mV voltage loss at 0.8 A cm-2 after 30,000 cycles and ignorable current degradation at a voltage of 0.6 V over 85 h. Comprehensive in situ experiments and theoretical calculations reveal that oxygen species spillover from Fe-N-C to PtFe alloy not only inhibits H2O2 production but also eliminates harmful oxygenated radicals. This work paves the way for the design of highly efficient and stable ORR catalysts and has significant implications for the development of next-generation fuel cells.

Control Over Nitrogen Dopant Sites in Palladium Metallene for Manipulating Catalytic Activity and Stability in the Oxygen Reduction Reaction

AbstractDoping light elements in Pt‐group metals is an effective approach toward improving their catalytic properties for oxygen reduction reaction (ORR). However, it is challenging to control dopant sites and to establish the correlation between the doping site and the catalytic property. In this paper, this success is demonstrated in controlling N doping sites in Pd metallene to manipulate electrocatalytic properties toward ORR. A Pd metallene sample with N dopant predominantly located at the atomic vacancy site (V‐N‐Pd metallene) exhibits two times higher mass activity in ORR than a Pd metallene sample with N dopant mainly occupied the interstitial site (I‐N‐Pd metallene). However, the I‐N‐Pd metallene shows improved durability than the V‐N‐Pd metallene, with only a 4 mV decay in half‐wave potential after 20 000 cycles. Computational calculation results reveal that the significantly enhanced ORR activity of V‐N‐Pd metallene arises from the atomic vacancy‐doped N, which modulates the electronic structure of Pd metallene to weaken the adsorption energy of intermediate O* species. This work provides guidelines for manipulating catalytic properties by controlling the doping sites of light elements in metal nanostructures.

Epitaxial growth of Pd clusters on N-doped Ag nanowires for oxygen reduction reaction

Efficient and stable Pt-free electrocatalysts for oxygen reduction reaction (ORR) are indispensable for future fuel cells. Herein, we describe a heterostructure of Pd nanocrystals (PdNCs) on N-doped Ag nanowires (NWs) synthesized using a direct epitaxial growth strategy with a Pd loading of only 9.5 wt.%. The PdAg bimetallic heterostructure showed the highest mass activity among reported PdAg-based ORR electrocatalysts and exhibited excellent stability, with only a 1.5 mV decay in the half-wave potential even after 20000 cycles of continuous testing. The remarkably enhanced activity and durability can be attributed to the distinct advantages of the ultrasmall PdNCs, cocatalysts of N-doped AgNWs, and their heterointerfaces. This work reveals that the epitaxial growth of a heterostructure on a stable support is a promising strategy for promoting catalytic performance.

Electronic Structure Engineering of Pt-Ni Alloy NPs by Coupling of Gold Single Atoms on N-Doped Carbon for Highly Efficient Oxygen Reduction Reaction and Hydrogen Evolution Reaction.

Improving the catalytic activity and durability of platinum-based alloy catalysts remains a formidable challenge in the context of renewable energy electrolysis applications. Herein, a facile and rapid photochemical deposition strategy for the synthesis of gold single atoms (Au SAs) anchored on N-doped carbon is presented. These Au SAs serve as a charge redistribution support for Pt-Ni alloy nanoparticles (PtNiNPs/AuSA-NDC), creating an extended electron-donating interface with Pt-Ni alloy sites. Consequently, the PtNiNPs/AuSA-NDC hybrid catalyst manifests exceptional catalytic performance and durability in both the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) under acidic conditions. Specifically, in ORR, it exhibits a half-wave potential (0.92V vs RHE), with a mass activity 20.4 times superior to Pt/C at 0.9V. In HER, PtNiNPs/AuSA-NDC demonstrates a notably reduced overpotential of 19.1mV vs RHE at 10mAcm-2 and a mass activity 38 times higher than Pt/C (at 0.25mV). Furthermore, this hybrid catalyst displays outstanding durability, with only an 8.0mV decay observed for ORR and a 6.9mV decay for HER after 10000 cycles. Theoretical calculations provide insight into the mechanism, demonstrating that isolated Au sites effectively modulate the electronic structure of Pt-Ni alloy sites, facilitating intermediate adsorption and enhancing reaction kinetics.

Wonton-structured KB@Co-C3N4 as a highly active and stable oxygen catalyst in neutral electrolyte for Zinc-air battery

This work addresses the challenges faced by oxygen catalysis applications in neutral media, which are hindered by sluggish kinetics and severe carbon corrosion. To overcome these issues, a bifunctional oxygen catalyst (KB@Co-C3N4) was developed by utilizing graphitic carbon nitride (g-C3N4) to support Co-Nx active sites and simultaneously to wrap Ketjen black (KB) to form a wonton structure. The resulting catalyst exhibited excellent ORR/OER activity and good stability in neutral electrolytes. The KB@Co-C3N4 catalyst demonstrated a half-wave potential (E1/2) of 0.723 V and only a 9 mV decay after 40000 cycles of ORR accelerated durability test (ADT). In terms of OER, the overpotential at 10 mA cm−2 (η10) of KB@Co-C3N4 was 550 mV, with negligible increase observed even after 20 k cycles of OER ADT. The zinc-air battery incorporating KB@Co-C3N4 exhibited superior performances over other benchmark bifunctional counterparts in open-circuit voltage (1.52 V), galvanostatic discharge/charge performance and cycling duration (985 h at 5 mA cm−2). The theoretical investigation revealed that the engineered electronic structures of the metal active sites enable precise regulation of the charge distribution of Co centers, leading to optimized adsorption and desorption of oxygenated intermediates. The high stability of the catalyst is attributed to the chemically stable C3N4, which strengthens Co-Nx active sites and protects KB against carbon corrosion by wrapping KB to form the wonton structure.

Synergetic effect of both cation and anion doping cobalt oxides on V2C MXene boosting oxygen evolution reaction

In order to enhance the conductivity and catalytic efficiency of non-noble electrocatalyst, an electrocatalysts consisting of ZnCo metallic double oxide with S doping embedded on V2C MXene for oxygen evolution reaction (OER) is synthesized. Cobalt serves as the primary active site, while zinc contributes to improve conductivity owing to its high electronegativity. Sulfur doping plays a crucial role in reducing the energy barrier of rate determining step of OER. The V2C MXene as a substrate can promote conductivity as well, resulting in synergistic effect. The electrocatalyst exhibits a low overpotential of 240 mV at 10 mA cm−2 in alkaline electrolyte, surpassing that of IrO2 commercial electrocatalyst. The potential shows only a minimal ∼5 mV day after 72-h stability test at 20 mA cm−2. The current density at 1.6 V vs RHE is 2 times that of commercial IrO2. Both theoretical calculation and experimental result demonstrate the advantage brought by the incorporation of zinc and sulfur. This work introduces a new idea of synergetic effect in non-noble metallic electrocatalysis.

Synthesizing Pd-based high entropy alloy nanoclusters for enhanced oxygen reduction.

We report the synthesis of uniform Pd-based high-entropy alloy clusters via rapid Joule heating. The quinary PdMnFeCuNi clusters exhibit 4.95 times higher mass activity than the Commercial Pt/C for the oxygen reduction reaction, and outstanding stability with only 2 mV decay in the half-wave potential after 20 000 cycles of testing.

In-situ growth of carbon nanotubes for improving the performance of Co-N/C catalysts in proton exchange membrane fuel cell

Cobalt-nitrogen/carbon (Co-N/C) was considered as the promising catalyst for oxygen reduction reaction (ORR). The combination of dense single-atom active site density and serviceable proton electronic conductivity is the key to improve the activity and stability of the catalyst in proton exchange membrane fuel cells. Herein, we achieved the in-situ growth of massive carbon nanotubes (CNTs) during the synthesis of Co-N/C catalysts by precisely regulating the ratio of reactants in the metal–organic framework precursors. Notably, the dense deformed Co-N4 sites were anchored on the in-situ grown CNTs, improving the triple-phase boundary and proton electronic conductivity of membrane electrode assemblies (MEA). Benefiting from the unique structure of dense Co-N4 sites anchored on CNTs, the target catalyst Co-N/C-1/4.4 exhibited high activity in both ORR (half-wave potential: 0.781 V, kinetic current@0.80 V = 2.25 mA cm−2) and fuel cell (H2-Air: 0.49 W cm−2) tests. And the in-situ grown CNTs with high graphitization degree led to a significant improvement in the stability of the catalyst (10 mV decay of half-wave potential after 30,000 cycles). We believe this research may provide new understanding into the development of non-PGM electrocatalysts with high performance at the atomic scale.

Synergistic Hybrid Electrocatalysts of Platinum Alloy and Single-Atom Platinum for an Efficient and Durable Oxygen Reduction Reaction.

Pt single-atom materials possess an ideal atom economy but suffer from limited intrinsic activity and side reaction of producing H2O2 in catalyzing the oxygen reduction reaction (ORR); platinum alloys have higher intrinsic activity but weak stability. Here, we demonstrate that anchoring platinum alloys on single-atom Pt-decorated carbon (Pt-SAC) surmounts their inherent deficiencies, thereby enabling a complete four-electron ORR pathway catalysis with high efficiency and durability. Pt3Co@Pt-SAC demonstrates an exceptional mass and specific activities 1 order of magnitude higher than those of commercial Pt/C. They are durable throughout 50000 cycles, showing only a 10 mV decay in half-wave potential. An in situ Raman analysis and theoretical calculations reveal that Pt3Co core nanocrystals modulate electron structures of the adjacent Pt single atoms to facilitate the intermediate absorption for fast kinetics. The superior durability is attributed to the shielding effect of the Pt-SAC coating, which significantly mitigates the dissolution of Pt3Co cores. The hybridizing strategy might promote the development of highly active and durable ORR catalysts.

Atomic iron coordinated by nitrogen doped carbon nanoparticles synthesized via a synchronous complexation-polymerization strategy as efficient oxygen reduction reaction electrocatalysts for zinc-air battery and fuel cell application

Developing atomic transition metal coordinated by nitrogen doped carbon (M−N−C) eletrocatalysts for oxygen reduction reaction (ORR) is critical to achieve low cost metal-air batteries and fuel cells. Herein, a general method of synthesizing M−N−C was developed via a synchronous complexation-polymerization strategy, in which nitrogen-containing ligand was coordinated with specific transition metal ions and diamino aromatic compound was simultaneously polymerized by the metal ion as initiator; by the following pyrolysis in a molten NaCl bath, M−N−C was finally synthesized. Fe-N-C was synthesized by this strategy using 2, 4, 6-Tri (2-pyridyl)-1, 3, 5-triazine (TPTZ) as ligand for FeCl2, and 1, 8-Diaminonaphthalene (DAN) as monomer of polymerization. Results demonstrate that introducing DAN into TPTZ-Fe2+ significantly affect the derived carbon structure and electrochemical performance of corresponding Fe-N-C. The Fe-N-C prepared by TPTZ and DAN with the molar ratio of 1:1 shows excellent ORR activity and durability, whose initial half-wave potential is 0.90 V in 0.1 M KOH and 0.80 V in 0.5 M H2SO4 respectively, after 10 K cycles, the potential is only 14 mV loss in 0.1 M KOH and 20 mV decay in 0.5 M H2SO4. And the ORR performance as cathode is further proved by a single practical Zn-air battery with a maximum power density of 192 mW cm−2 and a specific capacity of 800 mAh gZn-1, much higher than 137 mW cm−2 and 735 mAh gZn-1 of the same loading of commercial Pt/C catalyst and proton exchange membrane fuel cell with a high power output of 640 mW cm−2. Attributed to the vast kinds of ligands, metal ions and polymerizing monomers, this strategy provides a flexible platform of synthesizing advanced M−N−C catalysts, compared with other reported methods.

Exploiting H-induced lattice expansion in β-palladium hydride for enhanced catalytic activities toward oxygen reduction reaction

• We reported an efficient strategy to synthesis active and durable electrocatalysts of Pd hydride nanocubes (NCs) by hydrogen diffusion. • The obtained Pd hydride nanocubes are encapsulated within amorphous CuO, forming a core-shell structure to keep the hydrogen. • Obvious lattice expansion is founded in the PdH 0.43 @CuO catalysts. • The as-prepared PdH 0.43 @CuO catalyst exhibits excellent electrochemical performance for ORR. We have developed an efficient strategy to synthesize an active and durable electrocatalyst of Pd hydride nanocubes (NCs). Instead of the traditional chemical method, the PdH 0.43 NCs are firstly prepared via a hydrogen diffusion procedure, followed by hydrothermal synthesis of an amorphous CuO layer encapsulating the PdH 0.43 NCs to prevent the hydrogen atoms from escaping. Obvious lattice expansion is demonstrated playing a pivotal role in the enhancement of their oxygen reduction reaction (ORR) activity and durability. The obtained PdH 0.43 @CuO NCs catalysts exhibit an ORR mass activity of 0.18 A mg −1 at 0.90 V versus reversible hydrogen electrode in an alkaline medium, which is about five times higher than that of commercial Pt/C. Accelerated durability tests show that there is only a 32 mV decay in half-wave potential even after 10,000 potential cycles, indicating the excellent stability of PdH 0.43 @CuO NCs. Density functional theory (DFT) calculations also indicate that, compared to Pd, PdH 0.43 has a lower limiting barrier to form OH − during the ORR process. The present study illustrates the importance of lattice expansion caused by hydrogen and offers an available strategy to design highly efficient and durable Pd-based electrocatalysts for alkaline fuel cells.

Coupling the Atomically Dispersed Fe‐N3 Sites with Sub‐5 nm Pd Nanocrystals Confined in N‐Doped Carbon Nanobelts to Boost the Oxygen Reduction for Microbial Fuel Cells

AbstractBoth the monodispersed Pd/C (2–5 nm) and Fe‐NC single atoms (SAs) are promising non‐Pt catalysts for oxygen reduction reaction (ORR), which belongs to precious metal and nonprecious metal camps, respectively. However, the poles apart of sub‐5 nm Pd/C and Fe‐NC SAs in synthesis and thermostability leave the challenge to integrate them together in one system. Herein, a 1‐naphthylamine protected pyrolysis mechanism is devised to couple the atomically dispersed Fe sites with sub‐5 nm Pd nanocrystals embedded in N‐doped carbon nanobelts (FeN3‐Pd@NC NBs). The FeN3 SAs represent the minimal surface blockage to tune the electronic structure of Pd, while the carbon frameworks are born with ultrathin, porous, and N‐doped feature's. As inspired, the FeN3‐Pd@NC NBs exhibit outstanding activity (E1/2 = 0.926 V) and durability (2 mV decay in E1/2 after 2000 cycles) for ORR, as well as achieving a maximum power density of 831.2 mW cm−2 in a microbial fuel cell operated for over 100 d. Density functional theory calculation reveals that the FeN3 SAs can shift the density of states of Pd toward the Fermi level, and their coupling can decrease the limiting reaction barrier with a value of −0.62 eV, thus greatly accelerating the ORR kinetics.

Iridium in Tungsten Trioxide Matrix as an Efficient Bi-Functional Electrocatalyst for Overall Water Splitting in Acidic Media.

Electrocatalytic water splitting in acidic media is a promising strategy for grid scale production of hydrogen using renewable energy, but challenges still exist in the development of advanced catalysts with both high activity and stability. Herein, it is reported that iridium doped tungsten trioxide (Ir-doped WO3 ) with arrayed structure and confined Ir sites is an efficient and durable bi-functional catalyst for overall acidic water splitting. A low overpotential (258mV) is required to achieve an oxygen evolution reaction current density of 10mA cm-2 in 0.5 m H2 SO4 solution. Meanwhile, Ir-doped WO3 processes a similar intrinsic activity to Pt/C toward hydrogen evolution reaction. Overall water splitting using the bi-functional Ir-doped WO3 catalyst shows low cell voltages of 1.56 and 1.68V to drive the current densities of 10 and 100mA cm-2 , respectively, with only 16mV decay observed after 60 h continuous electrolysis under the current density of 100mA cm-2 . Structural analysis and density functional theory calculation indicate that the adjusted coordination environment of Ir within the crystalline matrix of WO3 contributes to the high activity and durability.

G-C3N4 templated synthesis of the tubular CoFe/N doped carbon composite as advanced bifunctional oxygen electrocatalysts for zinc-air batteries

Rational incorporating transition metal into porous heteroatom-doped carbon is intensively investigated as an effective strategy to achieve high-performance and bifunctional requirements. Herein, we fabricated the hollow composite that CoFe alloy nanoparticles decorated on the tubular N-doped carbon (denoted as T-CoFe/NC) by soft-templating strategy. In order to effectively incorporate the CoFe alloy into nitrogen doped hollow carbon matrix, g-C3N4 nanotubes were selected as the template to attain high contents of nitrogen doping for tubular carbon matrix. Meanwhile, the coordination effect between tannic acid and metal ions is utilized to limit the metal agglomeration in the process of pyrolysis. Consequently, the resultant catalyst shows an outstanding ORR activity with the half-wave potential of 0.86 V and outstanding stability with only a 2 mV decay after 10,000 cycles. T-CoFe/NC also displays comparable overpotential to the RuO2 at 10 mA cm−2. The high bifunctional electrocatalytic activity is attributed to the unique tubular structure and the combination of Co with Fe can optimize the interaction between the oxygenic species and metal surfaces, enhancing the catalytic activity. And T-CoFe/NC based zinc-air battery exhibits excellent power density, large capacity and good cycling stability.

Performance assessment of cathodically protected reinforced concrete structure based on alternative performance criterion: a case study

Performance of cathodic protection system in reinforced concrete structures is generally evaluated using 100 mV decay criterion. This approach is widely used, however has its own limitations. Recently, a new approach by determining the actual corrosion rate using the Butler Volmer equation has become an ‘alternative’ criterion for assessing the performance of cathodic protection system. This paper deals with critical examination and practical application of Butler-Volmer Equation to judge the effectiveness of cathodic protection system. Sensitivity analysis of various input parameters through numerical modelling by parametric studies showed significant dependence of corrosion rate on cathodic Tafel slope. One-year field data from a cathodic protection monitoring site in UK was collected and variability in the two approaches was assessed.

Boosting energy efficiency of Li-rich layered oxide cathodes by tuning oxygen redox kinetics and reversibility

In developing electrode materials for next-generation Li-ion batteries, significant efforts have been given to the energy, power density and cycling stability, with much less (if any) attention paid to the energy efficiency – arguably, the most important practical measure for large-scale applications. This is particularly true for the oxygen-redox active electrodes, such as Li1.2Ni0.13Co0.13Mn0.54O2, the notorious energy-inefficient cathode that has an extremely high capacity but comes with large voltage hysteresis and voltage decay. Herein, we report the rational design of an energy-efficient Li-rich layered cathode along with high energy, power density and cycling stability enabled by tuning oxygen redox activity. Specifically, the target material Li1.12Ni0.22Co0.13Mn0.52O2 exhibits an ultrahigh energy efficiency at 1 C (90.6%), high capacity (> 200 mAh g−1) with 98.9% retention and less than 150 mV decay at the extended 200 cycles. Through direct comparison between the material and Li1.2Ni0.13Co0.13Mn0.54O2, we show that the compositional change, although slightly, greatly improves the oxygen redox kinetics and reversibility, thereby boosts energy efficiency. The findings offer a strategy to narrow the gap between scientific interest and practical application of oxygen-redox chemistry.

Efficiency of cathodic prevention to control corrosion in seawater mixed concrete

Large amount of potable water is used in construction industry. Due to shortage of potable water, use of seawater for both mixing and curing concrete seems to be an ideal alternative. However, major drawback of using seawater in concrete is large amount of chloride present in it, which leads to corrosion of embedded reinforcement in concrete. The main objective of the present study is to explore use of Cathodic Prevention (CPre) technique to control corrosion and successfully use seawater for making concrete. In the present study, three types of specimens were tested, i.e. (i) mixed with potable water, (ii) mixed with seawater, and (iii) mixed with seawater and with CPre to compare corrosion rate in seawater mixed concrete and to check efficiency of CPre to control it. Corrosion in specimens was monitored using both direct current (HCP and LPR) and alternating current (ac) based (EIS) technique. Effectiveness of CPre is monitored both in terms of 100 mV decay criterion and using EIS. The results show that application of the CPre technique just after casting of concrete can allow successful use of seawater for making steel reinforced concrete. Moreover, compared to dc techniques, EIS technique provides more detailed and accurate data during monitoring of steel corrosion, CPre and it is more helpful in identifying prevalent corrosion control mechanisms in seawater mixed concrete.

A metal free electrocatalyst for high-performance zinc-air battery applications with good resistance towards poisoning species

The trace amount of poisoning species in air, such as SOx and NOx, greatly degrade the performance of zinc-air battery, as they block the active sites of conventional metal containing electrocatalysts. To overcome this challenge, a catalyst with enhanced electrocatalytic properties and good resistance towards the small molecular poisons should be prepared. In this work, we synthesized a P, N dual-doped porous carbon nanospheres (DDPCN), which showed an Eonset and E1/2 of 0.98 V and 0.87 V for ORR reduction in alkaline solution, and a Tafel slop of 72 mV/dec, over-performing all the other metal-free catalysts and comparable with the performance of state-of-the-art Pt/C (20 wt%). Moreover, the E1/2 for DDPCN showed negligible change towards poisoning species; while the E1/2 for Pt/C and typical CoOx/CNTs displayed 10/10 mV and 24/13 mV decay by adding trace amount of SO32−/NO2− into the electrolyte solution. By using DDPCN as the electrocatalyst for zinc-air battery application, the device showed the highest open circuit voltage (1.48 V), the highest power density (224 mW cm−2) and the highest energy density (874 W h kg−1) among all metal-free catalysts, and their performances are even better than the Pt/C catalyst. Moreover, these performances showed negligible influence by the poisoning species for DDPCN based Zn-air battery, while the performances for Pt/C and CoOx/CNTs based Zn-air batteries were greatly deteriorated by the poisoning species up to 25% and 40%.

Residual protection on a wharf structure following application of impressed current cathodic protection

Recent studies have suggested that residual protection is afforded to structures following the application of impressed current cathodic protection (ICCP), in some cases for significant periods of time, while others for periods of only a few days. This study reported the findings of the de-activation of a 20 year old ICCP system installed on a 50 year old structure. The ICCP was de-activated for 84 days and the steel potentials at locations on the front pile cap and front wall were monitored via the installed reference electrodes. An adjacent water anode system was also de-activated for 48 hours during the initial de-activation period to observe the impact on the steel potentials. The results showed that out of 42 reference electrodes, 17 achieved a 100 mv decay within 24 hours and 10 had more positive instant off potentials than -150 mV. Furthermore, all displayed a positive shift in potential following deactivation of the ICCP system for a period of time, indicative of residual protection, with 22 displaying this positive shift for the whole 94 days of the trial.