Marine carbon dioxide removal (mCDR) has emerged as a promising strategy for greenhouse gas removal (GHG-R) to support global net-zero emission targets and mitigate climate change. We present an mCDR approach that integrates seawater electrolysis with a Cl₂–H₂ fuel cell to achieve ocean de-acidification via CO₂ removal, while supplying renewable electricity by converting the Cl₂ byproduct back to the power grid. This system offers several advantages: (a) it mineralizes oceanic carbonates, creating a revenue stream (b) it provides energy storage capability, functioning analogously to a battery for marine renewable energy sources and (c) it employs robust, non-leaching catalysts compatible with marine environments. The Cl₂–H₂ fuel cell enables generation of reliable electricity production alongside an electrochemical pH swing that both captures dissolved CO₂ and promotes recovery of acidified marine ecosystems. We synthesized a series of Ruₓ₁%Ti100-x1%Oₓ2 (x₁ = 100, 30, 70) catalysts and integrate them into a seawater-tolerant, zero-gap membrane electrode assembly (MEA) electrolyzer. The system demonstrated a sustained operation for over 70 hours at 250 mA cm⁻² and maintained a stable polarization response across a wide current range (10–500 mA cm⁻²). Selectivity toward the chloride oxidation reaction (Cl-OR) was characterized using electrochemical mass spectrometry (EC-MS), achieving high selectivity rates at low current densities. To assess deployment feasibility, we performed a small-scale field analysis comparing system energy demands and identified optimal geographic sites using mCDR potential modeling. This work lays the groundwork for developing a scalable, renewable-powered, environmentally benign, and economically practical platform for carbon removal from the marine environment.
