Nitrogenases catalyze biological dinitrogen (N₂) reduction to ammonia (NH₃), and also reduce a number of non-physiological substrates, including carbon dioxide (CO₂) to formate (HCOO⁻) and methane (CH₄). Three versions of nitrogenase are known (Mo-, V-, and Fe-nitrogenase), each showing different reactivities towards various substrates. Normally, electrons for substrate reduction are delivered by the Fe protein component of nitrogenase, with energy coming from the hydrolysis of 2 ATP to 2 ADP + 2 Pi for each electron transferred. Recently, it has been demonstrated that energy and electrons can be delivered from an electrode to the catalytic nitrogenase MoFe-protein without the need for Fe protein or ATP hydrolysis. Here, it is demonstrated that both the MoFe- and FeFe-protein can be immobilized as a polymer layer on an electrode and that electron transfer mediated by cobaltocene can drive CO₂ reduction to formate in this system. It was also found that the FeFe-protein diverts a greater percentage of electrons to CO₂ reduction versus proton reduction compared to the MoFe-protein. Quantification of electron flow to products exhibited Faradaic efficiencies of CO₂ conversion to formate of 9% for MoFe protein and 32% for FeFe-protein, with the remaining electrons going to proton reduction to make H₂.

固氮生物催化二氮（N ₂）还原为氨（NH ₃），并且还减少了一些非生理底物，包括二氧化碳（CO的₂）至甲酸盐（HCOO ^- ）和甲烷（CH ₄）。已知三种形式的固氮酶（Mo-，V-和Fe-固氮酶），每种均显示出对各种底物的不同反应性。通常，用于底物还原的电子是由固氮酶的铁蛋白成分传递的，能量来自每个传递的2 ATP水解为2 ADP + 2 Pi的能量。近来，已经证明能量和电子可以从电极传递到催化的固氮酶MoFe蛋白，而无需Fe蛋白或ATP水解。在此证明，MoFe和FeFe蛋白都可以作为聚合物层固定在电极上，并且由钴茂介导的电子转移可以驱动CO _2。在该系统中还原成甲酸盐。还发现与MoFe蛋白相比，FeFe蛋白将更多百分比的电子转移到CO ₂还原而不是质子还原。产物电子流的定量显示法拉第效率，MoFe蛋白转化为甲酸的CO ₂转化为甲酸，FeFe蛋白转化为甲酸的32％，其余电子质子还原生成H ₂。