Highly efficient electrocatalytic hydrogen evolution from neutral aqueous solution by a water-soluble anionic cobalt(II) porphyrin.

We report the use of a water-soluble anionic cobalt(ii) tetrakis(p-sulfonatophenyl)porphyrin (CoTPPS) as a stable, active, and efficient catalyst for electrocatalytic H2 generation from neutral H2O without any organic additives. The molecule features nearly quantitative Faradaic efficiency with a turnover frequency of ∼1.83 s(-1) measured over 1 h and a turnover number of 1.9 × 10(4) moles of H2 per mole of catalyst with no loss of activity over 73 h at an applied potential of -1.29 V (vs. SHE) in neutral phosphate buffer solution.