How to produce Oxygen at Home

The procedure described below will realise the continuous production of oxygen gas in a home environment.

I have tested a basic technique for producing small amounts of oxygen gas reliably and simply.  Gas can be stored and used from a relatively low-pressure bladder, as needed.

I have no medical training - so am  not qualified to advise on any health-related applications for the procedure described. 

The technique employed, electrolysis, involves splitting water into hydrogen and oxygen using an electric current.  It is not a particularly efficient method - but the equipment needed can generally be found in a domestic environment. 

A zinc-plated bucket is the electrical cathode and copper piping serves as an anode.  (If other inert metals, other than copper, are available, e.g. stainless steel, nickel or platinum!, they may be suitable for the anode too).  Oxygen gas produced at the anode is collected by an inverted funnel (or neck of a bottle)…   hydrogen, produced at the cathode as a by-product, needs to be vented to the atmosphere and safely dispersed.

The addition of a small amount of a suitable impurity to the water helps facilitate the process (adding free ions) because pure water is not a good conductor of electricity.  One is effectivley creating an aqueous electrolyte.

The rate that oxygen can be produced will depend mainly on the magnitude of the electric current flowing between the electrodes, which, in-turn will depend on:

• the voltage of the direct current (D.C) power source;

• the effective surface area (and composition) of the electrodes - mainly the immersed anode;

• the conductivity of the electrolyte (water predominantly - affected slightly by it's temperature).

Theoretically, one kilogram of water (a litre) splits into 620 litres of oxygen and 1240 litres of hydrogen.  A human consumes about 550 litres of pure oxygen in 24 hours.

The oxygen content of normal air is c. 21%.

Precautions

Metals, liquid electrolytes, electricity and humans, when combined, do not make congenial bedfellows.  Particular care needs to be exercised with relatively high voltage, direct current - which, to be prudent, would be anything exceeding 50V.  Consider wearing rubber/latex gloves for protection and insulation.

Electric currents flowing through conductors (including electrolytes) will cause heat to be generated within them - very roughly proportional to the square of the current.

Dangerous substances, hazardous to humans, can be inadvertently produced by electrolysis.

Hydrogen gas is inflammable…  and when combined with oxygen in the right proportion, is explosive - but, being lighter than air, will float upwards, and, if allowed, dissipate in moving, free air.

Oxygen gas (slightly heavier than air - so it will collect at ground-level) will accelerate combustion processes.

What you'll need:

• a galvanized steel bucket - of over 8 litre capacity,

• a metal item to act as an anode - say, copper piping (or sheeting - possibly formed into a spiral), or nickel or galvanized metal or stainless-steel or platinum.  As the anode is in an oxygen-rich environment, the material will oxidize to an extent, eventually reducing its performance if not de-oxidized,

• multi-strand connection wire - say, 13 Amps (A) maximum rating,

• a source of direct electric current (D.C.) - say, 30V maximum, at a current rating of c. 10 A, 

• tap water - if it's been treated for human consumption, would ideally be de-chlorinated first (by say, vigorous shaking or letting it stand overnight),

•  sodium hydroxide (caustic soda)…  or sodium bicarbonate (bicarbonate of soda) or potassium hydroxide which are all alkaline…  or alternatively, dilute sulphuric acid,

• an empty, 2 litre plastic (drinks) bottle,

Using two lengths of connection wire:

• Connect the negative from the power source to the galvanized (zinc-plated) bucket (making it the cathode).  Large crocodile clips are effective. 

• Connect the positive from the power source to the copper (or other suitable metal) making it the anode.

Then:

1.   Half-fill the bucket with tap water.

2.   Add a few teaspoonfuls of sodium hydroxide (available in some drain cleaners) to improve the conductivity of the water - so increasing the volume of gas liberated.

3.   Apply electric power to the electrodes.

4.   Slowly immerse the metal anode into the water - preferably monitoring the current drawn.  The wetted surface area of the immersed anode will be one factor determining the overall current drawn - therefore the amount of oxygen released.  Ensure that the current drawn is kept below the maximum rating of the power supply.  Check that, when power is applied, there's no possibility of the anode contacting the metalwork of the bucket - as the resulting `short circuit´ may overload the power source, possibly damaging it or alternatively damaging the connection wiring…  or even causing sparking which could ignite combustible gases.

5.   If correctly configured, bubbles of oxygen will be produced on the anode.  (A layer of bubbles adhering to the anode [both outside and inside piping] will reduce the efficacy of gas production [indicated by declining current consumption]).
   
   Gas bubbles can be collected with an inverted, plastic funnel - or the upper-half of a plastic drinks bottle - placed over the anode:

   • cut the bottom off the bottle;

   • remove any cap so that the copper pipe can be inserted downwards through the neck of the bottle.  The bottle should cover the top of the piping to act as a ˋfunnelˊ collecting gas as it bubbles off the anode.

   • immerse the copper pipe, with its surrounding plastic bottle, into the water - the mouth (neck) of the bottle should be positioned just above the surface of the water;

   • there should be a gap of at least a centimetre between the base of the bottle/funnel and the bottom of the bucket.

A rather handy indicator of the pressure of liberated oxygen (over ambient air-pressure) is provided by the difference in height of liquid inside the funnel compared with the height of liquid outside it - so, up to about ten centimetres of water - relatively low.

It may be useful to include a `collection´/storage-bladder reservoir, say, a large plastic bag.  This should seal to the mouth of the bottle/funnel - and then gas extracted from the bladder.  (For drawing oxygen, one end of a canular could be sealed into the mouth of the bag.)

Water will be consumed as it´s broken-down into gases, so, for oxygen to be produced continuously, it'll need to be regularly topped-up.

As a refinement, the central area of the base of the bucket could be covered/coated to prevent - or divert - hydrogen bubbles forming on it and contaminating the harvested oxygen.