When astronauts are space walking they must carry oxygen tanks on their back, I’m curious to know the details of the air they breath, it’s storage and delivery.
What is the gas mix they breath?
Are they affected by O2 poisoning? If so, what partial pressure would be considered unsafe in no atmosphere?
What pressure (bar or psi) would the tanks hold?
How big (ltrs) are the air tanks
How is the air delivered, on demand or by some sort of constant feed?
Would oxygen last longer in space (no atmospheric pressure) than on earth?
The wikifor space suits should get you started, at least for some starter references. Here is a pdf from Nasa on the evolution of the space suit. Scroll through it and some of your questions are answered within it. E.g., the pressure within the suit is ~4.3 psi.
A 2000 list of Aerospace medicine papers for further reading.
To prevent an occurrence of the bends, crew members intending to go EVA spend a period of time prebreathing pure oxygen.During that time, nitrogen gas in the bloodstream is replaced by pure oxygen. Prior to prebreathing, the atmospheric pressure of the entire orbiter cabin is depressed from the normal 101 kilopascals to 70.3 pascals while the percentage of oxygen is slightly increased
Two tanks contain a total of 0.54 kilograms of oxygen at a pressure of 5,860.5 kilopascals. Although I’m sure it can hold higher pressure.
See above
The oxygen tank maintain a constant pressure by a pressure regulator adjusting flow. A centrifugal fan, running at nearly 20,000 rpm, draws the contaminated oxygen back into the PLSS at a rate of about 0.17 cubic meters per minute - process it and returns the Oxygen back to the suit.
Do not understand this question. Do you mean like humans will use less oxygen in space ? The spacesuits are designed for optimal use of oxygen and reuse of exhaled Oxygen - so in that way it lasts longer.