Sodium hypochlorite, the active ingredient in household bleach, has quietly become one of the world’s most essential chemicals. It disinfects drinking water, sanitizes hospitals, and controls biofouling in industrial plants. Yet most of it is manufactured in centralized facilities and shipped in tankers to the point of use, a logistics chain that is vulnerable to disruption, as the COVID-19 pandemic made painfully clear when commercial disinfectants vanished from shelves in many communities. A new study from researchers at the University of Cape Coast in Ghana, published in the journal Discover Electrochemistry, tackles a deceptively simple question: if you want to make your own disinfectant on site, which electrode material should you reach for? The answer, backed by a carefully controlled benchmarking experiment, is not the one you might expect.
Electrochemical generation of sodium hypochlorite is conceptually straightforward. When a sodium chloride brine is electrolyzed, chloride ions are oxidized at the anode to produce chlorine gas, which hydrolyzes in water to form hypochlorous acid and, in the bulk solution, hypochlorite. Meanwhile, water is reduced at the cathode, generating hydrogen gas and hydroxide ions that combine with the hypochlorite to yield sodium hypochlorite. The overall reaction can be written in simplified form as NaCl plus H2O yielding NaOCl plus H2. In practice, however, the process is riddled with competing pathways. Oxygen evolution at the anode steals electrons that should go to chlorine production, hypochlorite decomposes chemically, chlorine can volatilize out of solution, and elevated voltages drive secondary oxidation to chlorate. The efficiency of the whole enterprise therefore hinges on the electrode material and the geometry of the cell.
The industrial gold standard is the dimensionally stable anode, or DSA: a titanium substrate coated with mixed metal oxides such as ruthenium and iridium dioxide. These anodes achieve current efficiencies above 90 percent and last for years, but they are expensive and often inaccessible in the decentralized, resource-limited settings where on-site generation would be most valuable. Recent research has pushed the frontier further with titanium suboxide architectures, cost-efficient Ti–V–Sn–Sb electrodes, and even high-entropy alloy nanowires capable of selective chlorine evolution from seawater. What has been missing, the Ghanaian team argues, is something more mundane but arguably more practical: a fair, side-by-side comparison of the cheap, widely available materials that a workshop in a rural clinic or a small water utility could actually obtain.
That gap matters because most published electrochlorination studies examine a single electrode material under its own idiosyncratic conditions: different reactor geometries, electrolyte concentrations, hydrodynamics, and voltages. Differences in reported performance may therefore reflect the operating conditions rather than the intrinsic properties of the material. To eliminate this confounding, Samuel Kofi Tulashie and colleagues evaluated five accessible non-DSA materials—aluminum, copper, graphite, stainless steel, and platinum—under strictly identical conditions. Each material served as both anode and cathode in a membrane-less, stirred 250-milliliter batch cell containing 20 grams per liter of sodium chloride at near-neutral pH of 7.02. The team systematically varied the electrode spacing from 4 to 10 centimeters and the applied voltage from 6 to 12 volts, running each electrolysis for 40 minutes and quantifying accumulated free chlorine by iodometric titration at 10-minute intervals.
The first finding concerns geometry. Reducing the electrode spacing from 10 to 8 centimeters increased free chlorine formation for every material tested, an effect the authors attribute to reduced ohmic resistance in the solution, which lowers the required cell potential and increases the effective current delivered at a fixed applied voltage. But the trend did not continue monotonically. Shrinking the gap further to 6 and then 4 centimeters actually reduced free chlorine output, even though output at those spacings still exceeded the 10-centimeter case. The maximum at 8 centimeters suggests a sweet spot where electrical, mass-transport, and hydrodynamic effects are favorably balanced. Below the optimum, the researchers propose, concentration polarization and non-uniform current distributions may intensify competing side reactions, while the chlorine and oxygen bubbles generated at the electrodes can crowd together, partially blocking active sites and disrupting electrolyte flow. The authors are careful to note that bubble dynamics were not directly measured, so these explanations remain plausible interpretations rather than demonstrated mechanisms.
When it came to the materials themselves, graphite emerged as the clear winner, accumulating approximately 189 milligrams per liter of free chlorine after 40 minutes—the highest of any electrode. Stainless steel followed at roughly 156 milligrams per liter, copper at about 89, aluminum at about 75, and platinum, remarkably, brought up the rear at around 71 milligrams per liter. The graphite result is consistent with a growing literature on carbon-based electrochlorination and makes physical sense: graphite surfaces are relatively inert toward active chlorine, limiting catalytic decomposition and allowing hypochlorite to accumulate. Stainless steel performed well because the mixed iron-chromium oxide layers that form during anodic polarization remain sufficiently stable under these conditions to sustain chlorine production before extensive passivation sets in.
The underperformance of aluminum and copper tells a cautionary tale about corrosion. Under anodic polarization in chloride-rich electrolyte, copper readily forms Cu+ and Cu2+ species, while aluminum undergoes localized pitting corrosion once its passive oxide layer breaks down. Dissolved metal ions are known catalysts for active chlorine decomposition through redox cycling, so these electrodes effectively destroy the very product they generate. The modest, near-linear rise in free chlorine over time for these materials suggests that generation and decomposition proceeded simultaneously throughout the electrolysis. Platinum’s poor showing is more subtle and, in its way, more instructive. The noble metal sustained the highest current densities across the entire voltage range, yet converted only a small fraction of that charge into measurable free chlorine. The likely culprit is the competing oxygen evolution reaction, which on platinum diverts electrons away from chloride oxidation. The lesson is blunt: pushing more current through a cell does not guarantee more disinfectant.
To quantify this, the team calculated absolute Faradaic efficiencies for free chlorine formation, relating the moles of product to the total charge passed. For all electrodes, efficiency decreased as applied voltage rose, indicating that progressively more of the electrical charge was lost to parasitic pathways—oxygen evolution, chlorine volatilization, hypochlorite decomposition, corrosion reactions, and chlorate formation. Graphite and stainless steel posted the highest efficiencies across the voltage range, confirming their superior charge utilization, while platinum, aluminum, and copper lagged substantially. For the corroding metals, anodic dissolution itself consumed charge that should have gone to chlorine production. The authors emphasize that these figures represent system-level charge utilization rather than intrinsic chlorine-evolution selectivity, since iodometric titration measures total free chlorine without distinguishing species or accounting for oxychlorine by-products.
The study is candid about its limitations, which is part of what makes it useful. The experiments captured only short-duration performance in an undivided batch cell; long-term electrode stability, chlorate and perchlorate formation, specific energy consumption, and lifecycle cost were all beyond scope. Electrode geometries differed—flat plates for the metals, cylindrical rods for graphite and platinum—and the constant-voltage operation without a reference electrode means the results should be read as comparative system benchmarks, not intrinsic electrocatalytic rankings. Minor chlorine loss to the headspace of the open, stirred reactor may also have introduced a small negative bias. The authors call for future work with geometrically identical electrodes under constant-current conditions, extended operation, cyclic voltammetry, impedance spectroscopy, and techno-economic assessment.
Even with those caveats, the practical message is striking. Two of the cheapest, most universally available materials on the planet—graphite and stainless steel—delivered the best combination of disinfectant output and charge efficiency, outperforming platinum under these conditions. For communities and small utilities considering decentralized electrochlorination, where titanium-based DSAs may be unavailable or economically prohibitive, that is genuinely good news. It suggests that the barrier to safe, locally produced disinfectant is not exotic materials science but careful engineering of the cells we can already build, with the right electrode gap, the right voltage, and the right pair of humble electrodes immersed in salt water.
Subject of Research: Benchmarking of low-cost electrode materials for electrochemical sodium hypochlorite generation
Article Title: Benchmarking accessible electrode materials for electrochemical sodium hypochlorite production
Article References: Tulashie, S. K., Atiiga, A.-W. I., Mensah, S., Teye, S. O., Arkorful, R., Iddrisu, M., Olorunyomi, M. O., Nsiah, F., Zugle, R., Alimoh, G., Adukpo, G., & Koomson, S. (2026). Benchmarking accessible electrode materials for electrochemical sodium hypochlorite production. Discover Electrochemistry, 3(1), Article 64. https://doi.org/10.1007/s44373-026-00152-z
Image Credits: AI Generated
DOI: 10.1007/s44373-026-00152-z
Keywords: sodium hypochlorite, electrochlorination, graphite electrode, stainless steel, platinum, Faradaic efficiency, chlorine evolution, on-site disinfection, electrode spacing, water treatment, decentralized systems, electrochemistry
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Bethany Barker. (September 24, 2026). Cheap Electrodes Turn Salt Water Into Disinfectant, and Graphite Beats Platinum. Scienmag. https://scienmag.com/cheap-electrodes-turn-salt-water-into-disinfectant-and-graphite-beats-platinum/
Bethany Barker. “Cheap Electrodes Turn Salt Water Into Disinfectant, and Graphite Beats Platinum.” Scienmag, 24 September 2026, https://scienmag.com/cheap-electrodes-turn-salt-water-into-disinfectant-and-graphite-beats-platinum/. Accessed 24 September 2026.
Bethany Barker. “Cheap Electrodes Turn Salt Water Into Disinfectant, and Graphite Beats Platinum.” Scienmag. September 24, 2026. https://scienmag.com/cheap-electrodes-turn-salt-water-into-disinfectant-and-graphite-beats-platinum/
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Tags: chlorine evolutioncost-effective electrolysis methodsdecentralized disinfectant productiondecentralized systemselectrochemical synthesis of disinfectantselectrochemical water treatmentelectrochemistryelectrochlorinationelectrode material selectionelectrode spacingFaradaic efficiencygraphite electrodegraphite vs platinum electrodesinnovative electrode materials for water sanitizationon-site disinfectant productionon-site disinfectionplatinumsalt water chlorinationsalt water disinfectant generationsalt water electrolysissodium hypochloritesodium hypochlorite manufacturingstainless steelWater treatment
