Note: This chapter was removed from the NCERT curriculum in the 2022 rationalization. Retained here as electrolysis, electroplating, and electrochemical concepts connect to battery technology, hydrogen production, and materials science — GS3 topics.

Why this chapter matters for UPSC: Electrochemistry is the science behind two of India's most important energy policy priorities: green hydrogen production (National Green Hydrogen Mission, 2023) and domestic battery manufacturing (ACC PLI scheme, ₹18,100 crore). Electrolysis is also the basis of the chlor-alkali industry and corrosion-prevention technologies that protect billions in infrastructure investment annually.

PART 1 — Quick Reference Tables

Conductors vs Insulators of Electricity

Category Examples Why They Conduct (or Don't)
Good conductors Silver, copper, gold, aluminium; acids, bases, salt solutions (electrolytes) Free electrons (metals) or free ions (solutions) carry charge
Semiconductors Silicon, germanium Limited free electrons; conductivity tunable by doping
Poor conductors / Insulators Distilled/pure water, rubber, plastic, glass, dry wood, ceramics, dry air No free electrons or ions available

Note on pure vs impure water: Pure (distilled) water is a poor conductor. It conducts electricity only when dissolved salts, acids, or bases are present — providing free ions. Rainwater conducts because it dissolves CO₂ (forming carbonic acid) and dust particles. This explains why wet hands and electrical appliances are dangerous.

Electroplating — Metals and Applications

Metal Plated Base Material Purpose Industry
Chromium Steel (car parts, taps) Corrosion resistance + aesthetic shine Automotive, sanitary ware
Silver Copper/brass cutlery, jewellery Aesthetics, food safety Tableware, ornaments
Gold Jewellery base metals, electronic connectors Aesthetics; corrosion resistance; conductivity Electronics, jewellery
Nickel Steel machine parts Wear resistance, corrosion protection Engineering
Tin Steel (food cans) Food-safe, non-toxic barrier against rusting Food packaging
Zinc (galvanising) Iron/steel structures, pipes, roofing Sacrificial anode — zinc corrodes preferentially, protecting iron Construction, infrastructure

Battery Types Comparison

Battery Type Rechargeable Energy Density Key Uses
Zinc-carbon (dry cell) No Low Torches, remote controls, wall clocks
Alkaline (AA/AAA) No Moderate Consumer electronics; longer life than zinc-carbon
Lithium (non-rechargeable) No High Smoke detectors, cameras, medical implants
Lead-acid Yes Low (but cheap, reliable) Car starter batteries, UPS, inverters
Nickel-Metal Hydride (NiMH) Yes Moderate Older hybrid vehicles (e.g., Toyota Prius Gen 1/2)
Lithium-ion (Li-ion) Yes High Smartphones, laptops, EVs, grid storage
Lithium Iron Phosphate (LiFePO4) Yes Moderate-High Stationary storage, EVs (safer chemistry, longer cycle life)
Solid-state (emerging) Yes Very high Next-gen EVs (being commercialised 2025–30)

PART 2 — Detailed Notes

Chemical Effects of Electric Current (Electrolysis)

When an electric current passes through a conducting solution (electrolyte), it causes chemical decomposition — this process is called electrolysis. The container holds two electrodes connected to a battery:

  • Anode (+): Connected to the positive terminal; attracts negative ions (anions)
  • Cathode (-): Connected to the negative terminal; attracts positive ions (cations)

At the anode, oxidation occurs (electrons lost); at the cathode, reduction occurs (electrons gained). This is the foundation of all electrochemical processes — from electroplating to green hydrogen production.

Key Term

Electrolyte: A substance that dissolves in water to produce ions, enabling the solution to conduct electricity. Strong electrolytes (fully dissociate): HCl, NaCl, NaOH, KOH. Weak electrolytes (partially dissociate): acetic acid, carbonic acid. Non-electrolytes: sugar, alcohol, urea — dissolve but produce no ions.

Electrolysis of Water — Green Hydrogen

Pure water (H₂O) can be split into hydrogen and oxygen gases by passing a direct electric current through it (with a small amount of electrolyte added to improve conductivity):

  • At cathode (-): 2H⁺ + 2e⁻ → H₂ (hydrogen gas, colourless)
  • At anode (+): 4OH⁻ → 2H₂O + O₂ + 4e⁻ (oxygen gas)
  • Volume ratio: H₂ : O₂ = 2 : 1

When the electricity used for this electrolysis comes from renewable sources (solar, wind), the hydrogen produced is called green hydrogen — zero direct carbon emissions.

UPSC Connect

UPSC GS3 — National Green Hydrogen Mission (NGHM): Approved by Cabinet in January 2023. Key targets by 2030:

  • 5 MMTPA (million metric tonnes per annum) of green hydrogen production
  • 125 GW of additional renewable energy capacity to power electrolysers
  • ~₹8 lakh crore in total investment (public + private)
  • 1 lakh direct jobs created; significant reduction in fossil fuel import bill

Strategic Green Hydrogen Incentive Programme (SIGHT): Provides financial incentives for domestic electrolyser manufacturing and green hydrogen production under NGHM.

Applications of green hydrogen:

  1. Steel: Replace coking coal in blast furnaces (Direct Reduced Iron — DRI process) — India aims for green steel exports
  2. Fertilizers: Replace natural gas in ammonia (NH₃) synthesis (Haber-Bosch process) — India imports ~4 MMTPA of fertilizer feedstock currently
  3. Refining: Petroleum refineries use large quantities of hydrogen for desulphurisation
  4. Transport: Hydrogen fuel cell vehicles (FCEVs); IOCL and NTPC piloting hydrogen buses in India
  5. Long-duration energy storage: Hydrogen can be stored and converted back to electricity via fuel cells when solar/wind output is low

Green Hydrogen Hubs: Rajasthan and Gujarat identified as priority hub states due to high renewable energy potential and proximity to fertilizer/refinery industries.

Electrolysis of Brine — Chlor-Alkali Industry

Electrolysis of salt water (brine = NaCl + H₂O) produces three commercially vital products:

  • Chlorine gas (Cl₂) at anode — used in water disinfection, PVC plastic, bleaching powder (CaOCl₂), pharmaceuticals
  • Hydrogen gas (H₂) at cathode — used as fuel and chemical feedstock
  • Sodium hydroxide / Caustic soda (NaOH) in solution — used in paper and pulp, soap, textiles, aluminium refining, water treatment
Explainer

Why galvanising uses zinc, not gold: Zinc acts as a sacrificial anode — when the coating is scratched and both zinc and iron are exposed to moisture, zinc corrodes preferentially (more reactive than iron in the electrochemical series), protecting the underlying iron. Gold, being less reactive, would not provide this protection. The iron would still corrode if the gold coating were scratched.

Electroplating — Process and Industrial Importance

In electroplating:

  • The object to be plated is the cathode (connected to negative terminal)
  • The plating metal forms the anode (connected to positive terminal)
  • The electrolyte is a solution of a salt of the plating metal

Metal ions from the anode dissolve into solution and are deposited as atoms onto the cathode surface — building up a thin, uniform layer.

Economic and infrastructure significance:

  • Corrosion losses: Corrosion of metals (rusting of iron/steel) costs India an estimated 3–4% of GDP annually in infrastructure, industrial, and maintenance losses — electroplating and galvanising are primary prevention methods
  • Tin-plated food cans: Tin is non-toxic and prevents iron from contaminating food — critical for the processed food supply chain
  • Electronic contacts: Gold plating on connector pins prevents oxidation and ensures reliable electrical contact in computers, smartphones, and aerospace electronics

Battery Technology and India's Policy Push

UPSC Connect

UPSC GS3 — Advanced Chemistry Cell (ACC) PLI Scheme: The Production Linked Incentive (PLI) scheme for Advanced Chemistry Cell (ACC) batteries was approved in May 2021 with an outlay of ₹18,100 crore (approximately $2.2 billion). Objectives:

  • Achieve 50 GWh of domestic battery manufacturing capacity
  • Reduce India's dependence on imported batteries (currently ~95% from China and Japan)
  • Support the EV ecosystem (Faster Adoption and Manufacturing of Electric Vehicles — FAME II scheme)
  • Enable grid-scale Battery Energy Storage Systems (BESS) for renewable energy integration

Why domestic battery manufacturing matters:

  1. EV adoption: India targets 30% EV penetration by 2030; 80% of two-wheelers, 40% of buses, 30% of private cars
  2. Energy security: Lithium, cobalt, and nickel are critical minerals — India is exploring mining in Australia (Khanij Bidesh India Ltd — KABIL), Argentina, and domestic sources
  3. Grid stability: As solar and wind capacity grows, battery storage becomes essential to balance intermittent generation with demand

Rajasthan Battery Energy Storage System: SECI (Solar Energy Corporation of India) has tendered large-scale BESS projects in Rajasthan to support the state's massive renewable energy pipeline.

Lithium reserves in India: Significant lithium reserves were reported in Reasi district, Jammu & Kashmir in 2023 (estimated 5.9 million tonnes — one of the world's largest deposits) — under exploration by the Geological Survey of India (GSI). If confirmed and mined, this could transform India's battery supply chain.

UPSC Connect

UPSC GS3 — EV Ecosystem and Battery Chemistry: Lithium-ion batteries dominate current EVs due to high energy density (~250 Wh/kg) and falling costs (from ~$1,100/kWh in 2010 to ~$100/kWh in 2024 — BloombergNEF data). Key components:

  • Cathode: Lithium-based oxide (LiCoO₂, LiFePO₄, NMC — nickel-manganese-cobalt)
  • Anode: Graphite (current); silicon-graphite (emerging, higher capacity)
  • Electrolyte: Liquid lithium salt solution (flammable — fire risk; hence thermal management systems in EVs)

Solid-state batteries (next generation): Replace liquid electrolyte with solid ceramic/polymer — safer, higher energy density, faster charging. Toyota, Samsung, and Indian startups (Log9 Materials) are working on commercialisation by 2027–2030.

Thermal runaway: A critical safety concern in Li-ion batteries — uncontrolled exothermic reactions if punctured, overcharged, or exposed to high temperatures. Several EV fires in India (2021–2022) led to BIS standards for EV battery safety (AIS-038/AIS-156).

Exam Strategy

Prelims traps:

  • Pure/distilled water is a poor conductor — it conducts only when dissolved salts/ions are present; do not confuse with the common notion that "water conducts electricity"
  • In electroplating, the object to be plated is the cathode (negative), not the anode — a frequent reversal in MCQ options
  • Galvanising = coating iron with zinc (not tin, not chromium); tin plating is used for food cans
  • Green hydrogen = produced by electrolysis using renewable electricity only; "blue hydrogen" = from natural gas with carbon capture; "grey hydrogen" = from natural gas without capture
  • The NGHM target is 5 MMTPA by 2030 — not 5 GW (GW is a power unit, not hydrogen quantity)
  • ACC PLI outlay is ₹18,100 crore and targets 50 GWh capacity — both numbers recur in Prelims
  • Lithium reserves found in J&K (Reasi) in 2023 — not in Rajasthan or Jharkhand

Mains angles:

  • Green hydrogen as a decarbonisation strategy for hard-to-abate sectors (steel, fertilizers, shipping)
  • Critical minerals for battery supply chain — India's import dependence and diversification strategy (KABIL, FTA with Australia)
  • EV adoption challenges — charging infrastructure, battery cost, grid readiness

Previous Year Questions

Prelims:

  1. With reference to 'Green Hydrogen', consider the following statements:

    1. It is produced by the electrolysis of water using renewable energy
    2. India's National Green Hydrogen Mission targets 5 MMTPA of green hydrogen production by 2030
    3. Green hydrogen emits CO₂ at the point of use in fuel cells
      Which of the above is/are correct?
      (a) 1 only
      (b) 3 only
      (c) 1 and 2 only
      (d) 1, 2, and 3

  2. The PLI scheme for Advanced Chemistry Cell (ACC) batteries in India primarily aims to:
    (a) Reduce the retail price of consumer electronics using imported batteries
    (b) Build domestic battery manufacturing capacity of 50 GWh to support the EV ecosystem
    (c) Develop nuclear battery technology for defence applications
    (d) Replace diesel generators in rural areas with battery-powered microgrids

  3. Which of the following correctly describes the process of galvanising?
    (a) Coating iron with a layer of tin to prevent corrosion
    (b) Coating iron with a layer of chromium for aesthetic shine
    (c) Coating iron with a layer of zinc that acts as a sacrificial anode
    (d) Coating copper pipes with a layer of nickel for wear resistance

Mains:

  1. Examine the significance of the National Green Hydrogen Mission for India's energy security and climate commitments. What are the technological and economic challenges in achieving the 2030 targets? (CSE Mains 2023, GS Paper 3, 15 marks)

  2. India's dependence on imported batteries and critical minerals poses strategic vulnerabilities for its EV and energy storage ambitions. Discuss the policy measures India has taken to address this challenge. (CSE Mains 2022, GS Paper 3, 15 marks)