Bifunctional Electrocatalysis for Water Splitting Applications

Bifunctional electrocatalysis integrates the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) within a single material to drive overall water splitting. This approach addresses the challenge of coupling two half-reactions at comparable rates, thereby improving energy efficiency and simplifying device architecture. Key performance metrics include low overpotentials for both OER and HER, small Tafel slopes, high stability under alkaline or neutral conditions and scalable synthesis routes. Recent advances have centred on transition-metal compounds—especially cobalt sulfides such as Co₉S₈—engineered into nanostructured architectures, composites with conductive carbon backbones and heteroatom-doped frameworks. These strategies enhance active-site exposure, accelerate charge and mass transport and suppress catalyst degradation. The global significance of bifunctional electrocatalysts lies in their potential to lower the cost of green hydrogen production, facilitate off-grid and decentralised energy technologies and integrate with renewable electricity sources.

Research from Nature Portfolio

Ultrathin Co₉S₈ nanosheets vertically aligned on nitrogen- and sulfur‐doped reduced graphene oxide demonstrate a model architecture for bifunctional water splitting. The in situ growth strategy yields few-layer Co₉S₈ sheets with abundant edge sites that interface intimately with a conductive graphene matrix. This design achieves a low OER overpotential of ca. 266 mV at 10 mA cm⁻² and a Tafel slope around 75 mV dec⁻¹, while maintaining long-term durability in alkaline electrolytes. The synergy between Co₉S₈ and the heteroatom-doped carbon support promotes rapid electron transfer and efficient gas-bubble release, underscoring the benefit of hierarchical, two-dimensional architectures for water splitting.

Bifunctional Electrocatalysis for Water Splitting Applications publication trend

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

Technical terms

Bifunctional electrocatalysis: Catalytic performance enabling both OER and HER within a single material.

Oxygen evolution reaction (OER): Anodic half-reaction in water splitting that produces O₂.

Hydrogen evolution reaction (HER): Cathodic half-reaction in water splitting that produces H₂.

Overpotential: Extra potential beyond the thermodynamic requirement needed to drive a reaction at a specified rate.

Tafel slope: Parameter describing the voltage-current relationship, indicative of reaction kinetics.

Heteroatom doping: Introduction of non-metal atoms (e.g., N, S, P) into a host lattice to modify electronic structure and active-site properties.

References

1. Hollow TiO2@Co9S8 Core–Branch Arrays as Bifunctional Electrocatalysts for Efficient Oxygen/Hydrogen Production. Advanced Science (2017).
2. Co 9 S 8 @N,P-doped porous carbon electrocatalyst using biomass-derived carbon nanodots as a precursor for overall water splitting in alkaline media. RSC Advances (2017).
3. Ultrathin Co9S8 nanosheets vertically aligned on N,S/rGO for low voltage electrolytic water in alkaline media. Scientific Reports (2019).
4. Development of Co/Co9S8 metallic nanowire anchored on N-doped CNTs through the pyrolysis of melamine for overall water splitting. Electrochimica Acta (2021).