Bioelectrogeneration of Hydrogen Catalyzed by a Nickel-Reconstituted Myoglobin Catalyst Under Atmospheric Conditions

While native hydrogenase enzymes efficiently produce molecular hydrogen, their practical use is hindered by oxygen instability. To address this, an artificial metalloprotein, NiTSPC-Mb, was developed by incorporating a synthetic nickel tetrasulfonated phthalocyanine cofactor into an apomyoglobin scaffold. Tested under acidic, aerobic conditions for the hydrogen evolution reaction, the modified graphite electrodes significantly outperformed the isolated cofactor. The system achieved a current density of up to -18.7 mA cm-2 at -1.2V versus RHE and an overpotential of approximately 430mV. It also exhibited enhanced kinetics, lowering the Tafel slope from 320 to 212 mV/dec. Mass spectrometry confirmed molecular hydrogen production, showing up to a 78% higher hydrogen ion current than the isolated cofactor. Furthermore, long-term studies demonstrated sustained performance, maintaining up to 83% higher current density over 20 hours. The protein scaffold successfully prevents catalyst aggregation and enhances proton transfer, offering a robust strategy for stable, oxygen-tolerant bioelectrocatalysis.