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Catalyst deactivation is loss of catalytic activity during use. Regeneration in an ideal catalytic cycle does not rule out a separate damaging chemical reaction, blocking of a surface, or physical loss of catalyst from the apparatus. A route can also be slowed by diffusion to the surface or by accumulation of a reaction intermediate. Such effects limit the usefulness of a low schematic reaction energy barrier: measured throughput depends on the whole reaction mechanism and on transport. Demonstrating regeneration requires more evidence than observing a faster first run. For a recovered solid catalyst, a useful further comparison is a second run with fresh reactants, matched recovered amount, and the same mixing and temperature, alongside a fresh-solid run and a blank. Loss during recovery or residual reactants can otherwise imitate catalyst deactivation or apparent reuse. This is a proposed control, not an observation reported for the catalysed peroxide comparison.

In the catalysed peroxide comparison, copper(II) sulfate supplies dissolved ions before addition of sodium hydroxide forms a solid by precipitation. The comparison tests that solid-forming treatment rather than assuming the dissolved salt is itself an effective catalyst.

The University of Washington's Decomposition of H₂O₂ with MnO₂ describes a supervised demonstration using solid manganese dioxide and hydrogen peroxide listed as 30%. Its cylinder version uses a spatula to introduce the solid; the stated readout is immediate molecular oxygen bubbles and heat production. An alternate bottle version replaces the contents of a tea bag with the solid and suspends it above the liquid. Releasing the bag brings it into contact with the liquid. The bag-above-liquid stage supplies a before-contact comparison; the page gives no timed gas collection, replicated blank trials or quantitative reaction rates.^[ref]

The balanced net chemical equation is $2{\mathrm{H}}_2{\mathrm{O}}_2⟶2{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2$. Appearance of gas after contact supports a contact-dependent acceleration of decomposition under these conditions. It does not distinguish surface conversion from a contribution of dissolved material, establish regeneration, or measure an activation energy. The simultaneous heat release also means that temperature can change after contact. A matched no-solid comparison and an empty-bag comparison would test background decomposition and the bag's contribution; these are proposed controls, not reported trials. The catalysed peroxide comparison supplies a complementary inspected teaching experiment with separate single-addition and paired-addition comparisons.