How long will it take to produce hydrogen?

Answer 1

Since hydrogen is natural occurring process and chemical you cannot produce hydrogen without there even being a trace of hydrogen already in another substance.

So according to wikipedia here is part of your answer:

H2 is produced in chemistry and Biology laboratories, often as a by-product of other reactions; in industry for the hydrogenation of unsaturated substrates; and in nature as a means of expelling reducing equivalents in biochemical reactions.

Laboratory

In the laboratory, H2 is usually prepared by the reaction of acids on metals such as zinc with Kipp's apparatus. Zn + 2 H+ → Zn2+ + H2

Aluminium can also produce H2 upon treatment with bases: 2 Al + 6 H2O + 2 OH− → 2 Al(OH)4− + 3 H2

The electrolysis of water is a simple method of producing hydrogen. A low voltage current is run through the water, and gaseous oxygen forms at the anode while gaseous hydrogen forms at the cathode. Typically the cathode is made from platinum or another inert metal when producing hydrogen for storage. If, however, the gas is to be burnt on site, oxygen is desirable to assist the combustion, and so both electrodes would be made from inert metals. (Iron, for instance, would oxidize, and thus decrease the amount of oxygen given off.) The theoretical maximum efficiency (electricity used vs. energetic value of hydrogen produced) is between 80-94%. 2H2O(aq) → 2H2(g) + O2(g)

In 2007, it was discovered that an alloy of aluminum and gallium in pellet form added to water could be used to generate hydrogen. The process also creates alumina, but the expensive gallium, which prevents the formation of an oxide skin on the pellets, can be re-used. This has important potential implications for a hydrogen economy, since hydrogen can be produced on-site and does not need to be transported.

The other part ot your question is: almost instantly when using the methods above

Answer 2

The time it takes to produce hydrogen using methods such as electrolysis or steam reforming depends on factors like the size of the production facility, technology efficiency, and desired production rate. It can range from seconds to hours, with industrial-scale facilities typically taking longer than smaller lab-scale setups.