Mesoporous Electrodes Enhance the Electrocatalytic Performance of [FeFe]‐Hydrogenase

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The metalloenzyme [FeFe]‐hydrogenase is of interest to future biotechnologies targeting the production of “green” hydrogen (H 2 ). We recently developed a simple two‐step functionalized procedure to immobilize the [FeFe]‐hydrogenase from Clostridium pasteurianum (“ Cp I”) on mesoporous indium tin oxide (ITO) electrodes to achieve elevated H 2 production with high operational stability and current densities of 8 mA cm −2 . Here, we use a combination of atomic force microscopy (AFM), scanning electron microscopy (SEM) and electrochemical quartz crystal microbalance (EQCM) to understand how mesoporous ITO stabilizes and activates Cp I for electroenzymatic H 2 production. Examination of the topography and morphology of the mesoporous ITO surface revealed a hierarchical morphology containing cavities and well‐defined nanoparticle agglomerates. Any potential effect of mesoporosity was investigated by comparing the stability and electroenzymatic activity of Cp I on mesoporous ‘nanoITO’ and planar ITO, where we determined that Cp I has a higher turnover frequency and adsorbs with greater stability (with respect to electroenzymatic activity over time) to nanoITO surfaces.