Morphological control of electrodeposited iron for fluctuating photovoltaic electrical energy

Abstract

With the Paris Agreement, the installed capacity of green power, such as photovoltaic (PV) and wind power, is growing rapidly at a rate of more than 10 % per year. The practical application of these green electrical energies is limited by the relative lag in the scale of energy storage systems. In response to the pressure on energy storage systems, we explored the feasibility of supplying DC power directly from a PV plant to an industrial electrolyzer by comparing the electrodeposition behavior of Fe2+ in a sulfuric acid system from stabilized DC and fluctuating PV power sources. We found that the factor that damages the stable operation of an iron electrodeposition system the most is the presence of hydrogen evolution reactions, where the generation of hydrogen bubbles reduces the current efficiency of the electrodeposition system and, in severe cases, destroys the surface morphology of the deposited products, causing devastating damage to the system. On this basis, we designed a simple scheme that uses heterogeneous bubble nucleation instead of homogeneous bubble nucleation for rapid bubble expulsion from the cathode surface. Benefiting from the rapid transfer of bubbles, the current efficiency of the electrodeposited iron system increases by 1.25%–10 % at different current densities, and the maximum roughness decreases by 129–2,396 nm, which considerably improves the stability of the electrodeposited iron system for PV power. This work provides useful experimental support for the transformation of the traditional steel smelting industry, which is characterized by high carbon emission and energy consumption, into an environmentally friendly industry.