{'fraction_non_alphanumeric': 0.029644268774703556, 'fraction_numerical': 0.01383399209486166, 'mean_word_length': 4.72316384180791, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Active Sites of Single-Atom Iron Catalyst for Electrochemical Hydrogen Evolution.

Electrochemical water splitting in alkaline media is an attractive way to produce the clear and renewable hydrogen fuel H2. In this work, we report a single-atom Fe1/NC catalyst, where the Fe-Nx moiety works as the active site, for high-efficiency alkaline hydrogen evolution reaction (HER). The Fe1/NC electrocatalyst exhibits a low overpotential of 111 mV at the current density of 10 mA cm-2, with a Tafel slope of 86.1 mV dec-1 in 1 M KOH solution. Operando X-ray absorption spectroscopy reveals that, under the working states, the Fe-support interaction weakened as the Fe-N coordination number and Fe oxidation state decreased. As such, the evolved single-atom Fe site with more d electrons provides a favorable structure for boosting HER performance. This work gives insight into the structural evolution of the active site under the alkaline HER and provides a strategy for the design of non-noble metal electrocatalysts.