Faradaic Quantized Capacitance as an Ideal Pseudocapacitive Mechanism

Abstract

In this work, we provide a theoretical analysis of quantized capacitance (also referred to as solvated Coulomb blockade) as a pseudocapacitive energy storage mechanism. In particular, we examine how redox species exhibiting quantized capacitance might be engineered to satisfy two basic criteria in the design of an “ideal” pseudocapacitive energy storage mechanism: (1) a near-rectangular voltammetric profile which mimics that of double-layer capacitance and (2) a linear rise in the pseudocapacitive current with respect to the voltammetric scan rate. It is demonstrated that nanoparticles exhibiting quantized capacitance may satisfy the first criterion by tailoring their charging and reorganization energies. It is also shown that the second criterion can be satisfied so long as the voltammetric scan rate does not exceed the electron-transfer rate. By formulating a comprehensive theoretical framework for understanding the electron-transfer properties of quantized capacitance, we arrive at a general phenomenological description of how pseudocapacitive properties might be practically engineered through this mechanism.