(52g) Promoting the Volmer-Step Via Charge Transfer at the Interface of Pt/Carbon-Substrate Towards Efficient Alkaline Hydrogen Evolution

Cost-effective production of green hydrogen powered renewable electricity is crucial for accelerating the transition to sustainability. Nowadays, hydrogen production via anion exchange membrane-based (AEM) water electrolyzer has attracted extensive research interests due to the rapid development of efficient anodic catalysts based on earth-abundant materials rather than the iridium-based catalysts in alkaline electrolytes. However, the kinetics of hydrogen evolution reaction (HER) in alkaline media electrolyte suffers severe declines compare to that of in acidic electrolyte even for the state-of-the-art HER catalyst Pt, whose activity in alkaline electrolyte ranges from one to a few orders of magnitude lower than that in acidic electrolyte. While this anomalous non-Nernstian pH effect on HER remains a puzzle, it is recognized that the Volmer step (*+H2O+e-→H*+OH-) is commonly the rate-limiting-step for alkaline HER. Therefore, various of strategies have been explored to facilitate the Volmer step, for instance, decorating the Pt surface with metal hydroxide (e.g., Ni(OH)2), tuning the valence-state and coordination environment of the atomically dispersed Pt, employing the strong metal–support interactions, etc. While carbon-based supports have been widely utilized for Pt-based HER catalysts owning to their large surface area, sufficient conductivity and good chemical stability, it is rare, if not none, that strong metal–support interactions are observed when using carbon substrates. However, it is desirable to introduce such substrate effects to carbon-based substrates, so that the catalyst fabrication processes can be largely simplified while the benefits of efficient mass/charge transfers can be retained. In this work, we report a new carbon-support which can significantly promote the Pt-based alkaline HER. Detailed kinetic analysis and mechanistic investigation reveal that the charge transfer at the Pt/carbon interface could greatly facilitate the Volmer step, resulting an activity enhancement of more than an order of magnitude compared to the state-of-the-art commercial Pt/C catalyst. We further demonstrate the high activity of our catalyst in an AEM electrolyser, which exhibits decent operating performance (1.0 A cm-2 at cell voltage of 1.87 V, energy efficiency of 66.3%) without further optimizations of the different electrolyzer components. Overall, we believe the new insights obtained in this work provide effective catalyst design principles that can guide the future development of active alkaline HER catalyst.