Studying nickel deposition with EQCM-D and EC-Raman

Significance of the topic

Electrochemical Quartz Crystal Microbalance with Dissipation monitoring (EQCM-D) combined with in situ Raman spectroscopy provides a powerful multimodal approach to study mass, viscoelastic properties and chemical state of electrodeposited films. This combination is particularly relevant for research into battery electrode materials and electrocatalysts where both mechanical integrity and redox-driven compositional changes (for example Ni(OH)2 ⇄ NiOOH) determine performance and lifetime. The methodology enables quantitative mass/thickness monitoring, mechanical characterization of deposited layers, and simultaneous chemical identification when integrated with EC-Raman, improving mechanistic understanding and accelerating materials optimization.

Objectives and overview of the study

• Demonstrate the capabilities of a combined EQCM-D and potentiostat (Metrohm Autolab AUT204 + 3T analytik eSorptionProbe OS) to monitor nickel hydroxide deposition onto a gold QCM crystal and to follow electrochemical cycling.
• Show how dissipation (damping) data complements frequency shifts to distinguish rigid vs. viscoelastic films and to infer surface roughness/topography during growth.
• Integrate EQCM-D with EC-Raman to obtain in situ vibrational fingerprints of the electrochemically driven transformation between Ni(OH)2 and NiOOH.

Methodology

The experimental campaign comprised three parts:

• Part 1 — Galvanostatic deposition of Ni(OH)2 onto a 10 MHz Au QCM crystal (active area 19.2 mm2) at 100 μA for 300 s in 50 mmol·L−1 NiSO4 (two-electrode cell, Pt counter).
• Part 2 — Cyclic voltammetry of the deposited film in 0.1 mol·L−1 NaOH (three-electrode cell, Ag/AgCl reference) to cycle Ni(OH)2 ⇄ NiOOH and monitor reversible mass changes.
• Part 3 — Electrochemical roughening (to produce a SERS-active surface) using chronoamperometry and linear sweep voltammetry in a DRP-RAMANCELL-M EC-Raman cell (0.1 mol·L−1 KCl electrolyte), followed by deposition and EC-Raman monitoring during potential steps.

Data acquisition: simultaneous recording of electrochemical signals (NOVA software with AUT204/FRA32M) and EQCM-D frequency/dissipation (qGraph/qGraph Viewer). Raman spectra were collected with an i-Raman Plus 532H (100% laser power, 20 s integration ×3 averages), with timing coordinated through DIO triggers; because of light-induced detuning (LID) only pre/post spectra were acquired during some sequences.

Used instrumentation

• Metrohm Autolab AUT204 potentiostat/galvanostat with FRA32M module.
• 3T analytik eSorptionProbe OS EQCM-D system (fundamental and overtone monitoring; focus here on fundamental frequency).
• 10 MHz Au QCM crystals (active area 19.2 mm2) mounted in insertable probes compatible with CORR250.CELL.S and DRP-RAMANCELL-M.
• i-Raman Plus 532H Raman spectrometer (EC-Raman cell integration).
• Software: NOVA (potentiostat control), qGraph and qGraph Viewer (synchronization and analysis of EQCM-D and electrochemical data).

Main results and discussion

• Deposition mass and rigidity: Galvanostatic deposition produced a resonance frequency shift of approximately −9500 Hz, corresponding (by the Sauerbrey relation with Cf = 4.3 ng·cm−2·Hz−1) to roughly 41,000 ng·cm−2 of deposited material on the crystal. The dissipation change was small (<10% of the frequency shift), indicating a largely rigid Ni(OH)2 layer for which the Sauerbrey approximation is applicable.
• Dissipation as a morphological probe: The dissipation trace initially increased and then returned to near zero as deposition progressed. This behaviour was interpreted as initial island-like growth producing hydrodynamic coupling with the electrolyte (increased damping), followed by coalescence into a continuous rigid film (damping reduction). Thus dissipation provided insight into surface roughness and the presence/absence of dendritic growth.
• Electrochemical cycling: CV cycling of the deposited film exhibited reversible mass changes. Approximately 1500 ng·cm−2 of mass was reversibly added/removed during redox cycling (Ni(OH)2 ⇄ NiOOH), equivalent to an ≈±3 nm thickness change. Both frequency and dissipation returned nearly to baseline under the tested conditions, indicating largely reversible intercalation of water and electrolyte cations and limited irreversible side reactions over the few cycles performed.
• EC-Raman chemical identification: After electrochemical roughening to create an enhanced Raman surface, EC-Raman spectra acquired at oxidizing potentials (NiOOH) showed diagnostic peaks at ~476 and 556 cm−1, while Ni(OH)2 was effectively Raman inactive in the 200–800 cm−1 region under the conditions used. The combined EQCM-D / EC-Raman sequence confirmed the electrochemical transformation between the two phases and illustrated challenges arising from light-induced detuning when collecting simultaneous QCM and Raman data.

Benefits and practical applications

• Quantitative mass monitoring: EQCM-D provides high-sensitivity mass/thickness measurements during electrodeposition and electrochemical cycling, suitable for battery electrode and catalyst studies.
• Mechanical and morphological insight: Dissipation yields information about viscoelasticity and surface roughness that cannot be obtained from frequency alone, enabling discrimination between rigid films, porous deposits and dendritic growth.
• Multimodal characterization: Integration with EC-Raman yields synchronous chemical information (oxidation state and phase identification), allowing direct correlation of redox processes with mass/structural changes.
• Versatility: The probe configuration is compatible with standard electrochemical cells and Raman cells, facilitating adoption in labs studying corrosion, energy storage electrodes, electrocatalysis and electroplating.

Future trends and potential uses

• Higher temporal and spectral integration: Improving synchronization and mitigating light-induced detuning will enable truly simultaneous EQCM-D and Raman monitoring during dynamic electrochemical protocols.
• Advanced viscoelastic modelling: For softer or more complex films, combining overtone analysis with appropriate viscoelastic models will increase accuracy of mass/thickness and mechanical property extraction.
• Expanded multimodal workflows: Coupling EQCM-D/EC-Raman with in situ impedance, optical or acoustic techniques will deepen mechanistic insight for next-generation battery and catalyst materials.
• Application to operando device studies: Scaling probes and cells for realistic electrode geometries could bridge the gap between model studies and full cell behaviour (e.g., Ni-based battery cathodes, electrocatalyst layers).

Conclusion

The application note demonstrates that combining a Metrohm Autolab AUT204 potentiostat with a 3T analytik eSorptionProbe EQCM-D enables detailed, in situ investigation of nickel hydroxide deposition and electrochemical cycling. Frequency shifts provided quantitative mass loading, dissipation traces revealed morphological evolution during growth, and EC-Raman identified the redox-active NiOOH phase. The integrated approach is broadly useful for battery materials and electrocatalysis research and highlights opportunities for further methodological improvements in simultaneity and modelling.

References

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