We know for a fact that there is a general trend between the atomic number of an element and it's radioactivity, the larger the atomic number, the more radioactive it becomes due to a less stable structure of the nucleus (of course there are occasional exceptions to this trend but it's generally consistent) which has a somewhat direct (yet unpredictable) effect upon radioactive decay.
Radioactive decay is the the process by which radioactive particles spontaneously split from the nucleus, and whilst there are various forms of decay, one particular type is beta (β) decay which involves the emission of either a negatively charged electron, or a positively charged positron (the anti-particle of the electron). The electron itself is an elementary particle used for the formation of atoms but not the nuclei, so electrons are essentially recyclable. In addition to this, a proton is produced from the decaying neutron.
In terms of allocating new protons and neutrons necessary for the formation of a Hydrogen atom (strictly speaking, neutrons aren't required in terms of the composition of the nucleus), occurrences known as nuclear spallations result in the ejection of neutrons due to the impacts of cosmic rays within the earth's atmosphere (these reactions also occur on the surfaces of objects such as meteorites), and these neutrons can then yield protons after beta decay. Since a single proton is all it takes to form a Hydrogen atom, you get an H+ ion.
Of course with theories such as the big crunch, all matter within the universe would be reduced to it's most fundamental form allowing for the reformation of the simplest element, Hydrogen.