Electrochemical Water Splitting for Hydrogen Production

Electrochemical water splitting employs electrical energy to drive the decomposition of water into hydrogen and oxygen at paired electrodes immersed in an electrolyte. At the cathode, protons or water molecules are reduced to yield H₂, while at the anode hydroxide ions or water are oxidised to produce O₂. The overall reaction is highly endothermic, requiring efficient catalysts to lower activation barriers and minimise overpotentials. Two principal commercial approaches are alkaline electrolysis, which uses a liquid alkaline electrolyte and porous diaphragms, and proton-exchange membrane (PEM) electrolysis, which employs solid polymer membranes for ion conduction. Recent innovations span cell architecture, materials and bubble management, targeting reduced energy consumption, simplified balance-of-plant and resilience to varying feed-water quality. Advances in bifunctional electrocatalysts based on earth-abundant elements, coupled with optimised mass transport at high current densities, have driven cell voltages ever closer to the thermodynamic minimum of 1.23 V. Scale-up of these technologies is central to global decarbonisation, offering a route to green hydrogen from renewable electricity for industry, transport and energy storage.

Research from Nature Portfolio

Recent studies have demonstrated a capillary-fed electrolysis cell in which a porous separator wicks water to electrodes via capillary action, eliminating bubble adhesion. This design achieves a cell voltage of 1.51 V at 0.5 A cm⁻² and 85 °C, corresponding to 98 % energy efficiency and an energy consumption of 40.4 kWh kg⁻¹ hydrogen, surpassing commercial benchmarks. By maintaining inherently bubble-free interfaces, the system simplifies auxiliary pumping and gas-liquid separation, paving the way for lower capital costs.

Another development involves a membrane-free flow electrolyser with a sandwich-like architecture and cyclic operation. Two physically separated compartments circulate H₂-rich catholyte and O₂-rich anolyte, enabling decoupled overall water splitting. With bifunctional catalysts based on abundant materials and efficient mass transport, the cell sustains 750 mA cm⁻² at 2.1 V in both deionised and tap water, delivering >99 % pure hydrogen and demonstrating the promise of hybridising alkaline and PEM concepts through architectural innovation.

Electrochemical Water Splitting for Hydrogen Production publication trend

The graph below shows the total number of articles in electrochemical water splitting for hydrogen production across all publications each year (not limited to Nature Index journals).

Technical terms

Overpotential: The additional voltage required beyond the thermodynamic potential to drive an electrochemical reaction at a given rate.

Bifunctional catalyst: A material that actively catalyses both the hydrogen-evolution and oxygen-evolution reactions.

Polymer electrolyte membrane (PEM) electrolyser: An electrolyser employing a solid ion-conducting polymer to separate anodic and cathodic compartments.

Alkaline electrolyser: An electrolyser using a liquid alkaline solution (e.g. KOH) and porous separator to conduct hydroxide ions.

Capillary-induced transport: Movement of liquid through a porous medium driven by surface tension forces, used to supply reactant water to electrodes without external pumps.

References

1. A high-performance capillary-fed electrolysis cell promises more cost-competitive renewable hydrogen. Nature Communications (2022).
2. A membrane-free flow electrolyzer operating at high current density using earth-abundant catalysts for water splitting. Nature Communications (2021).
3. Review of next generation hydrogen production from offshore wind using water electrolysis. Journal of Power Sources (2024).
4. Voltage losses in zero-gap alkaline water electrolysis. Journal of Power Sources (2021).