General Design of Aligned-Channel Porous Carbon Electrodes for Efficient High-Current-Density Gas-Evolving...

Gas-evolving reactions (GERs) are important in many electrochemical energy conversion technologies and chemical industries. The operation of GERs at high current densities is critical for their industrial implementation but remains challenging as it poses stringent requirements on the electrodes in terms of reaction kinetics, mass transfer, and electron transport. Here the general and rational design of self-standing carbon electrodes with vertically aligned porous channels, appropriate pore size distribution, and high surface area as supports for loading a variety of catalytic species by facile electrodeposition are reported. These electrodes simultaneously possess high intrinsic activity, large numbers of active sites, and efficient transport highways for ions, gases, and electrons, resulting in significant performance improvements at high current densities in diverse GERs such as urea oxidation, hydrogen evolution, and oxygen evolution reactions, as well as overall urea/water electrolyzers. As an example, the carbon electrode decorated with Ni(OH)₂ demonstrates a record-high current density of 1000 mA cm^-2 at 1.360 V versus the reversible hydrogen electrode, largely outperforming the conventional nickel foam-based counterpart and the state-of-the-art electrodes.