Surface Engineering of 3D Gas Diffusion Electrodes for High-Performance H2 Production with Nonprecious Metal Catalysts

In this work, a methodology is demonstrated to engineer gas diffusion electrodes for nonprecious metal catalysts. Highly active transition metal phosphides are prepared on carbon-based gas diffusion electrodes with low catalyst loadings by modifying the O/C ratio at the surface of the electrode. These nonprecious metal catalysts yield extraordinary performance as measured by low overpotentials (51 mV at -10 mA cm(-2)), unprecedented mass activities (>800 A g(-1) at 100 mV overpotential), high turnover frequencies (6.96 H-2 s(-1) at 100 mV overpotential), and high durability for a precious metal-free catalyst in acidic media. It is found that a high O/C ratio induces a more hydrophilic surface directly impacting the morphology of the CoP catalyst. The improved hydrophilicity, stemming from introduced oxyl groups on the carbon electrode, creates an electrode surface that yields a well-distributed growth of cobalt electrodeposits and thus a well-dispersed catalyst layer with high surface area upon phosphidation. This report demonstrates the high-performance achievable by CoP at low loadings which facilitates further cost reduction, an important part of enabling the large-scale commercialization of non-platinum group metal catalysts. The fabrication strategies described herein offer a pathway to lower catalyst loading while achieving high efficiency and promising stability on a 3D electrode.