The study investigates ion (de)solvation kinetics at solid–electrolyte interfaces, focusing on bipolar membranes and electrolyte–metal interfaces. Key findings include: 1. **Bias-Dependent Relationships**: The activation entropy and enthalpy show bias-dependent relationships, linked to interfacial capacitance dispersion. 2. **OH⁻ Solvation Kinetics**: OH⁻ solvation is kinetically slower than H⁺ solvation, and the kinetics are independent of catalyst structure. 3. **Universal Excess Charge**: A universal amount of excess charge is needed to induce electric fields that alter the interfacial entropy of water. 4. **Fundamental Importance**: These results are crucial for designing bipolar membranes and electrocatalysts, enhancing energy conversion technology. 5. **Interfacial Ion (de)solvation**: The process occurs whenever ions need to shed or gain their shell of dipolar solvents at charged interfaces. 6. **Electrochemical Bias**: The applied bias manifests as a shift in the free enthalpy of solvated protons and changes in interfacial capacitance. 7. **Catalyst Dynamics**: Interfacial capacitance impacts structural catalyst dynamics, with complete redox transitions leading to substantial atomic restructuring. 8. **Bipolar Membranes (BPMs)**: BPMs are used in electrodialysis, offering pH control and selective ion flow, but their function is not well understood. 9. **Ion Solvation in BPMs**: Ion solvation in BPMs is studied using a H2–H2 BPM fuel cell/H2 pump, revealing bias-dependent changes in pre-exponential factors and activation energies. 10. **Surface Configurational Entropy-enthalpy Compensation**: The pre-exponential factor and activation energy are linked to interfacial capacitance, with compensation effects observed. 11. **Bias-Dependent Capacitance**: Bias-dependent capacitance plays a crucial role in structural catalyst dynamics, affecting interfacial water dynamics. 12. **Multiphysics Model**: A semi-empirical multiphysics model is developed to account for Nernst–Planck transport and Arrhenius rate laws, providing a comprehensive understanding of ion solvation kinetics. 13. **Generalizability**: The findings are applicable to various interfaces, including polymer–polymer and electrolyte–metal interfaces, highlighting the universal nature of ion (de)solvation kinetics. These results provide a new perspective on electrocatalysis and electrochemistry, emphasizing the importance of considering bias-dependent interfacial capacitance and entropy-enthalpy relationships.The study investigates ion (de)solvation kinetics at solid–electrolyte interfaces, focusing on bipolar membranes and electrolyte–metal interfaces. Key findings include: 1. **Bias-Dependent Relationships**: The activation entropy and enthalpy show bias-dependent relationships, linked to interfacial capacitance dispersion. 2. **OH⁻ Solvation Kinetics**: OH⁻ solvation is kinetically slower than H⁺ solvation, and the kinetics are independent of catalyst structure. 3. **Universal Excess Charge**: A universal amount of excess charge is needed to induce electric fields that alter the interfacial entropy of water. 4. **Fundamental Importance**: These results are crucial for designing bipolar membranes and electrocatalysts, enhancing energy conversion technology. 5. **Interfacial Ion (de)solvation**: The process occurs whenever ions need to shed or gain their shell of dipolar solvents at charged interfaces. 6. **Electrochemical Bias**: The applied bias manifests as a shift in the free enthalpy of solvated protons and changes in interfacial capacitance. 7. **Catalyst Dynamics**: Interfacial capacitance impacts structural catalyst dynamics, with complete redox transitions leading to substantial atomic restructuring. 8. **Bipolar Membranes (BPMs)**: BPMs are used in electrodialysis, offering pH control and selective ion flow, but their function is not well understood. 9. **Ion Solvation in BPMs**: Ion solvation in BPMs is studied using a H2–H2 BPM fuel cell/H2 pump, revealing bias-dependent changes in pre-exponential factors and activation energies. 10. **Surface Configurational Entropy-enthalpy Compensation**: The pre-exponential factor and activation energy are linked to interfacial capacitance, with compensation effects observed. 11. **Bias-Dependent Capacitance**: Bias-dependent capacitance plays a crucial role in structural catalyst dynamics, affecting interfacial water dynamics. 12. **Multiphysics Model**: A semi-empirical multiphysics model is developed to account for Nernst–Planck transport and Arrhenius rate laws, providing a comprehensive understanding of ion solvation kinetics. 13. **Generalizability**: The findings are applicable to various interfaces, including polymer–polymer and electrolyte–metal interfaces, highlighting the universal nature of ion (de)solvation kinetics. These results provide a new perspective on electrocatalysis and electrochemistry, emphasizing the importance of considering bias-dependent interfacial capacitance and entropy-enthalpy relationships.