The numbers back up how much this field matters. The global electrochemical sensors market alone was valued at $10.4 billion in 2023 and is projected to reach $18.4 billion by 2030, according to Grand View Research's 2024 market report. This blog breaks down how electrochemical cells work, the main types you'll encounter, and how researchers now study these reactions at the nanoscale.
Key Takeaways
- Electrochemical cells convert chemical energy to electricity—or use electricity to drive non-spontaneous reactions
- Galvanic cells (batteries) generate power spontaneously; electrolytic cells require external voltage
- The Nernst equation predicts cell voltage shifts from concentration, temperature, and reactant activity
- Nanoscale AFM/STM imaging now lets researchers watch electrode reactions in real time
What Is Electrochemistry?
Electrochemistry studies the relationship between chemical reactions and electrical current. It centers on redox reactions—reduction-oxidation processes that move electrons between species.
- Oxidation is the loss of electrons from a molecule or atom.
- Reduction is the gain of electrons.
These two processes always happen together. One species can't lose electrons unless another gains them. This electron handoff, when controlled and channeled through a circuit, is what generates usable electrical current.
In the lab and in industry, electrochemistry underpins:
- Batteries and fuel cells
- Electroplating and metal finishing
- Corrosion science and protective coatings
- Chemical and biological sensors
- In-situ studies of electrode surfaces and interfaces
What Is an Electrochemical Cell? Core Components
An electrochemical cell converts chemical energy into electrical energy, or uses electrical energy to drive a reaction that would not occur on its own. Every cell type uses the same core parts.
Anode and Cathode
The anode is where oxidation happens. The cathode is where reduction happens.
Here's where it gets confusing: the polarity flips depending on cell type. In a galvanic cell, the anode is negative. In an electrolytic cell, the anode is positive. Same names, opposite charges. That swap trips up a lot of students.
Electrolyte and Ion Transport
The electrolyte allows ions to migrate between electrodes, completing the internal circuit. Without it, electrons would flow through the external wire but nothing would balance the charge inside the cell.
- Aqueous electrolytes: water-based solutions, common in Daniell cells and lead-acid batteries
- Non-aqueous electrolytes: organic solvents used in lithium-ion batteries, where water would react dangerously with lithium
Salt Bridge / Separator
A salt bridge connects two half-cells without letting their solutions mix directly. It allows ion flow to maintain electrical neutrality while keeping the reactants separated. Typical salt bridge electrolytes, like KNO₃ or KCl, are chosen because their cations and anions move at roughly equal speeds, minimizing junction potential errors.
External Circuit and Measurement Devices
Electrons flow through an external wire, not through the solution. This flow can power a device or be measured directly. Voltmeters read the cell's voltage, while potentiostats offer researchers active control over the potential applied to a system.
Three-Electrode Systems in Research
Lab-grade electrochemistry rarely uses just two electrodes. Instead, researchers rely on three:
- Working electrode — where the reaction of interest occurs
- Counter electrode — completes the circuit, carrying current
- Reference electrode — provides a stable potential baseline for measurement
This setup lets scientists control potential precisely while measuring current independently, which is essential for studying reaction mechanisms. The same three-electrode control underpins in-situ electrochemical AFM and STM, where surface structure is imaged as the cell runs.
Two Main Types of Electrochemical Cells
Electrochemical cells split into two categories based on whether the reaction happens spontaneously or needs a push.
Galvanic (Voltaic) Cells
Galvanic cells run on spontaneous redox reactions. The reaction proceeds on its own, and the cell harvests that energy as electricity. The anode is negative, the cathode is positive.
Real-world examples:
- Daniell cell — the classic zinc-copper setup that launched practical battery design
- Alkaline and lithium-ion batteries — everyday power sources in devices and vehicles
- Fuel cells — convert chemical energy from hydrogen or other fuels directly into electricity
Electrolytic Cells
Electrolytic cells go the other direction. They use externally supplied electricity to force a non-spontaneous reaction forward. Polarity reverses here: the anode becomes positive, the cathode negative.
Real-world examples:
- Electroplating — applying a thin metal coating, such as silver, onto another surface
- Water electrolysis — splitting H₂O into hydrogen and oxygen gas, requiring more than 1.229 V to proceed
- Hall-Héroult process — industrial aluminum extraction from alumina; developed independently by Hall and Héroult in 1886 and still the dominant method
Other Notable Cell Types
- Concentration cells — identical electrodes with different ion concentrations in each half-cell; voltage comes only from the concentration gradient
- Reference/standard cells (e.g., Weston cell) — stable, known voltages for calibration; NIST reports a calculated saturated Weston cell potential of 1.01840 V at 25°C versus measured 1.0184185 V
The Science Behind Cell Behavior
Standard electrode potentials tell you whether a reaction will run spontaneously and how much voltage a cell can produce under ideal, textbook conditions. Real-world conditions rarely match that ideal, though.
The Nernst equation adjusts that ideal voltage for real conditions. It calculates cell potential when concentrations differ from standard states:
E = E° - (RT/nF) ln Q
- E — actual cell potential
- E° — standard cell potential
- R — gas constant
- T — temperature in kelvin
- n — number of electrons transferred
- F — Faraday's constant
- Q — reaction quotient
At room temperature (298 K), this simplifies to E = E° - (0.0592/n) log Q. When the reaction reaches equilibrium, Q equals the equilibrium constant, and E drops to zero.
Electrode potential is only part of the story. Mass transport also limits how a cell behaves under load:
- Diffusion — random ion movement driven by concentration gradients
- Migration — ion movement driven by the electric field itself
- Convection — bulk fluid motion, often from stirring or flow
These mass-transport mechanisms, combined with reaction kinetics at the electrode surface, set how much current a cell can sustain once concentration and field effects take over.
Real-World Applications of Electrochemical Cells
Electrochemical cells power devices, treat waste streams, and enable clinical diagnostics across energy, industrial, and medical settings.
Energy storage and conversion
- Lithium-ion and alkaline batteries power phones, tools, and EVs
- Fuel cells convert hydrogen into electricity for vehicles and backup power
- Sodium-ion batteries are advancing as a lower-cost option; Argonne National Laboratory announced a $50 million consortium in November 2024 to push the technology forward
- Solid-state batteries are in active development for higher safety and energy density
Environmental and industrial uses
- Resistometric sensors track metal corrosion and degradation in real time
- Electroplating deposits controlled metal coatings while cutting process waste
- Water-treatment sensors detect heavy-metal contamination with biopolymer-based electrochemical designs
Medical and biosensor applications
- Glucose biosensors have reached detection limits as low as 1.25 nM with roughly 95% stability in lab testing
- Implantable batteries support pacemakers and other long-life medical devices
- Electrochemical immunoassays and wearable patches enable rapid point-of-care biomarker checks
These same cell chemistries drive materials and interface research, where electrode surfaces, SEI layers, and corrosion films are studied at the nanoscale.
Studying Electrochemical Cells at the Nanoscale
Bulk measurements like voltage and current tell you that a reaction happened. They don't show you how it happened at the electrode surface, where atoms are actually rearranging.
That's the gap nanoscale imaging fills. Researchers need to watch film growth, ion adsorption, and surface morphology changes in real time, at resolutions far below what optical tools can capture.
In-situ electrochemical AFM and STM make this possible. Researchers have used this approach to observe:
- Battery cathode surface changes during charge-discharge cycles in organic electrolytes
- Copper electrodeposition on Au(111) surfaces, tracking nucleation and crystal growth atom by atom
- Corrosion processes on metallic materials under controlled electrolyte conditions
At Molecular Imaging, our 5500 PicoPlus AFM+STM platform supports this kind of in-situ electrochemical work. Key capabilities include:
- Liquid-cell compatibility across acidic, basic, and organic-solvent environments
- Scan ranges from 9 × 9 µm for atomic-resolution detail up to 90 × 90 µm for broader surface mapping
- Environmental isolation chambers and temperature-controlled stages (−30°C to 250°C) for stable, long-running experiments
For labs studying molecular electronics or materials science alongside electrochemistry, a modular liquid-compatible setup lets one platform cover multiple research directions without separate dedicated instruments.
Frequently Asked Questions
What is an electrochemical cell?
An electrochemical cell is a device with an anode, cathode, and electrolyte that either converts chemical energy into electrical energy or uses electricity to drive a chemical reaction. Ions move through the electrolyte while electrons flow through an external circuit.
What is the purpose of an electrochemical cell?
Its purpose depends on the type: galvanic cells generate usable electrical power from spontaneous reactions, while electrolytic cells use external electricity to force reactions like electroplating or electrolysis to occur.
What are two types of electrochemical cells?
Galvanic (voltaic) cells produce electricity from spontaneous reactions, like batteries. Electrolytic cells consume electricity to drive non-spontaneous reactions, like water electrolysis or metal refining.
What is a real-life example of an electrochemical cell?
Household alkaline batteries, car lead-acid batteries, and hydrogen fuel cells are all galvanic cells. Electroplating baths and aluminum smelting via the Hall-Héroult process are common electrolytic examples.
What is the difference between a battery and a fuel cell?
A battery stores its reactants internally and depletes them over use, requiring recharging or replacement. A fuel cell continuously converts externally supplied fuel, like hydrogen, into electricity as long as fuel keeps flowing.
Why is the salt bridge important in a galvanic cell?
The salt bridge allows ions to flow between half-cells to maintain charge balance, without letting the two electrolyte solutions mix directly. Without it, the circuit would stop functioning almost immediately.
