(581g) Co-Mo-TiO2 Composite Electrocatalyst for the Hydrogen Evolution Reaction

Co-Mo alloys are recognized as excellent electrocatalysts for the hydrogen evolution reaction.^1-3 Presented here, micro-scale TiO₂ particles were captured into Co-Mo electrodeposited alloys to create a composite cathode with enhanced catalytic performance towards water electrolysis. The Co-Mo-TiO₂ composite thin films were fabricated galvanostatically from citrate electrolytes. The addition of a small amount of TiO₂ particles to the Co-Mo matrix did not alter the metal alloy composition ratio. The HER polarization and Tafel slopes were characterized in 1 M sodium hydroxide, and surface area was examined in a ferricyanide electrolyte. At the maximum value of the alloy exchange current density, the addition of TiO₂ further increased its value by approximately 3-5 times. The overpotential at -10 mA/cm² also showed a favorable reduction when particles were present in the deposit compared to their alloy counterparts. This improvement of HER parameters is not merely due to surface roughness but mostly an intrinsic one. The Tafel slope of all deposits with and without TiO₂ were similar, suggesting a common mechanism. The added TiO₂ may help to minimize the local increase in hydroxide concentration, facilitating the Heyrovsky step in a Volmer-Heyrovsky mechanism. This work may reveal a new way to improve transition-metal based HER electrocatalysts.

References

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3. Zhang, Q. Shao, S. Long, X. Huang, Nano Energy 45, 448 (2018).