<p>Renewable energy sources, such as solar and wind power, fluctuate on timescales of seconds to hours. Harnessing such intermittent energy to drive chemical synthesis represents a major challenge, as conventional 3<i>d</i>-block metal catalysts are prone to degradation even under small variations in operating potential. Here we report an electrochemical oxygen evolution reaction system that is tolerant to voltage fluctuations through the design of catalytic pathways. By leveraging the redox chemistry of manganese oxide, we integrated the Guyard reaction (4Mn²⁺ + Mn⁷⁺ → 5Mn³⁺) as a regeneration pathway into the catalytic cycle. Unlike other 3<i>d</i>-block metal catalysts, which rapidly degrade under fluctuating conditions, the constructed manganese oxide system shows resilience to voltage fluctuations by alternating between decomposition and regeneration. When the voltage is switched between 1.68 and 3.00 V repeatedly, the catalyst can maintain an oxygen evolution reaction at pH 2 for more than 2,000 h, highlighting the importance of pathway design for sustainable energy conversion from intermittent renewable sources.</p>