Probing the microwave induced overheating at electrode surface using a combined electrochemical and fluorescence method

Microwave (MW) activated electrochemical processes are hypothesized to be dominated by localized overheating at electrode surfaces under MW irradiation. Yet, direct measurement of the temperature near an electrode during MW irradiation was challenging due to the lack of spatiotemporally resolved techniques. Here, we introduce a metal–organic framework (MOF) modified indium tin oxide (ITO) electrode paired with a thermosensitive electrochemical reaction (naphthalene diimide, NDI redox reaction), which uniquely enables in-situ probing of dynamic temperature gradients at the electrode-solution interface under MW irradiation. Based on the experimental results, the spatiotemporal resolution of temperature gradient at the electrode/electrolyte solution interface is described by a heat transfer model, suggesting that the local overheating of ITO electrode leads to a temperature gradient of 2.7–4.7 °C between the MOF layer and the bulk solvent, and the gradient increases by increasing the MW field intensity. This approach advances existing methods by combining MOF-based thermal sensing with electrochemical measurements, overcoming the limitations of conventional thermometry in microwave environments. Additionally, a strategy was proposed to estimate the localized temperature of a MOF-modified ITO electrode using a thermosensitive electrochemical reaction under MW irradiation. This represents a novel framework for quantifying microwave-induced thermal effects, which has not been previously achieved with comparable precision. The redox peak of MOF linker NDI radical reaction on the cyclic voltammetry increases by 0.5 × 10⁻⁴ A with the temperature rise of 10 °C. By analyzing the plots of limiting current values against temperature, we can estimate the temperature at the overheated electrode surface based on the voltammetric responses to MW irradiation.