Herein, we present an innovative approach for transforming commonly available cellulose paper into a flexible and catalytic current collector for overall water splitting. A solution processed soak-and-coat method of electroless plating was used to render a piece of paper conducting by conformably depositing metallic nickel nanoparticles, while still retaining the open macroporous framework. Proof-of-concept paper-electrodes are realized by modifying nickel-paper current collector with model electrocatalysts nickel-iron oxyhydroxide and nickel-molybdenum bimetallic alloy through electrodeposition route. The paper-electrodes demonstrate exceptional activities towards oxygen evolution reaction and hydrogen evolution reaction, requiring overpotentials of 240 and 32 mV at 50 and −10 mA cm−2, respectively, even as they endure extreme mechanical stress. The generality of this approach is demonstrated by fabricating similar electrodes on cotton fabric, which also show high activity. Finally, a two-electrode paper-electrolyzer is constructed which can split water with an efficiency of 98.01%, and exhibits robust stability for more than 200 h.

The scope of any metal oxide as a catalyst for driving electrocatalytic reactions depends on its electronic structure, which is correlated to its oxygen‐defect density. Likewise, to transform a spinel oxide, such as cobalt ferrite (CoFe2O4), into a worthy universal‐pH, bifunctional electrocatalyst for the hydrogen and oxygen evolution reactions (HER and OER, respectively), oxygen defects need to be regulated. Prepared by coprecipitation and inert calcination at 650 °C, CoFe2O4 nanoparticles (NPs) require 253 and 300 mV OER overpotentials to reach current densities of 10 and 100 mA cm−2, respectively, if nickel foam is used as a substrate. With cost‐effective carbon fiber paper, the OER overpotential increases to 372 mV at 10 mA cm−2 at pH 14. The NPs prepared at 550 °C require HER overpotentials of 218, 245, and 314 mV at −10 mA cm−2 in alkaline, acidic, and neutral pH, respectively. The intrinsic activity is reflected from turnover frequencies of >3 O2 s−1 and >5 H2 s−1 at overpotentials of 398 and 259 mV, respectively. If coupled for overall water splitting, the extremely durable two‐electrode electrolyzer requires a cell potential of only 1.63 V to reach 10 mA cm−2 at pH 14. The homologous couple also splits seawater at impressively low cell voltages of 1.72 and 1.47 V at room temperature and 80 °C, respectively.