Good day, Busuyi Omoniyi! Hope you are doing well.

Seems that you are right - dilution with water might end the oxidative capacity. Analyzing market, we may mention, that commercial 50% H2O2 contains stabilizers, that prevent H2O2 decomposition:

https://www.sigmaaldrich.com/PL/pl/product/sigald/516813

https://www.solvay.com/en/product/interox-chemical-grade-50-hydrogen-peroxide

Pretty basic and interesting info I've found on patent documents:

"Stabilizers are normally added to hydrogen peroxide solutions to combat decomposition due to trace impurities, mainly dissolved metals. These compounds are usually sequestering agents and can take many forms. Many types of compounds have been used to fill this function, such as diols, quinones, stannate salts, pyrophosphates, various aromatic compounds and amino carboxylic acids salts. However, many of the previously suggested compounds have various issues and challenges associated with them, such as toxicity, environmental impact and poor performance. Examples of specific compounds that have been suggested for use in solutions to protect against hydrogen peroxide decomposition include sodium phenolsulfate; sodium stannate; N,N - lower alkyl aniline, sulfamic acid, sulfolane, and dinormal lower alkyl sulfones and sulfoxides; phosphonic acids and their salts; acrylic acid polymers; polyphosphates; polyamino polyphosphonic acids and/or their salts; and specific combinations (or blends) of such compounds. However, in addition to toxicity and environmental impact concerns, many of these suggested compounds or blends have other drawbacks. For example, use of the specific stabilizer(s) either require specific conditions to provide adequate hydrogen peroxide stability, such as specific pH levels, e.g., acidic conditions, or relatively low hydrogen peroxide concentrations, or have poor stability performance. The poor stability performance can either be poor stability performance generally or poor stability performance in specific formulations that contain other destabilizing components, e.g., surfactants." Link is provided:

https://patentimages.storage.googleapis.com/09/40/e0/a4354777423faf/EP2225175B1.pdf

Thus, it is always better to use, lets call it "producent-certified" oxidative agents, as far handling will cause its degradation. However, you may try to combine H2O2 dilution with with water-stabilizer system, and report your results on its oxidative capacity - it would be very interesting to know.

Feel free to mention me in your response in case of any extra questions.

Best of luck in your research!

Yours sincerely,

M. Sc. Vadym Chibrikov

Department of Microstructure and Mechanics of Biomaterials

Institute of Agrophysics, Polish Academy of Sciences

If this is a procedure that you are going to do routinely, it is better to dilute the 50% solution to 30% or less. This is because 50% H2O2 poses a fire danger if it comes in contact with many organics. Even 15-30% H2O2 can pose a fire danger if it's spilled on a flammable material such as paper towels and (erroneously) allowed to "dry" off, because water evaporates much faster than H2O2 and the remaining solution becomes more concentrated in H2O2.

However, the DI water you use for dilution should be of high purity, especially in terms of concentration of transition metals such as Fe, Cu, etc. These ions catalyze the decomposition of H2O2, and a substantial concentration of such ions may overcome the effect of decomposition inhibitors that are routinely present in commercial 50% H2O2.

As for oxidation capability - it doesn't matter whether you reach your final dilution in one or two steps, as long as you didn't cause partial decomposition of the H2O2 in the way described above.