This water fuel development and another one similar to it - does not mention "dense hydrogen" - only efficient water splitting.
https://www.nature.com/articles/s41467-019-13415-8 This technique is claimed to be the most efficient electrolysis/ water-splitting cell yet discovered. The catalyst used - a mix of iron oxide and nickel are both associated with dense hydrogen - either the Mills effect of the Holmlid effect. Thus, there is a decent chance that in addition to normal splitting water - this technique involves the densification of some of the H2 gas as it evolves. No attempt is made to collect it, of course, since the mainstream does not accept the findings of Mills or Holmlid, so using the output gas itself as secondary catalyst or excess energy source - was not considered. Given the future importance of hydrogen - even migrating to a possible "hydrogen economy" in the future - additional catalysis or energy derived from utilizing dense hydrogen should be looked at closer (under the assumption that UDH is now only an incidental or unplanned part of the process and not optimized).
