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oai:figshare.com:article/34027575 2026-09-29T20:12:29Z category_4 category_21 category_24 category_272 category_873 category_64 portal_63 item_type_6 month_year_09_2026

Oxidation-State Control of Cobalt Electrocatalysts Enables Selective Hydrogenation of Nitrogen-Containing Aromatics Akizumi Yonezawa (18618515) Yugo Shimizu (1832470) Juri Harada (14444671) Ryo Kurihara (19796975) Atsuki Hirama (22967224) Yusuke Muto (18618512) Reno Fukui (25138848) Ayaka Wakasugi (25138851) Koji Harano (1453105) Kazuhide Kamiya (1678105) Shoji Iguchi (3930176) Naoki Shida (2073136) Mahito Atobe (1946827) Biochemistry Biotechnology Evolutionary Biology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Cancer stable cell voltage reductive molecular transformations langmuir – hinshelwood generating hydrogen equivalents ex situ characterization electronically suitable environment containing aromatic compounds abundant heterogeneous electrocatalysts 750 ° c 0 )/ coo situ co k finely tuned co electronically tuned co selective electrocatalytic hydrogenation abundant cobalt catalysts supported cobalt catalyst reductive electrolysis conditions ambient electrolysis conditions pyridine hydrogenation proceeds 2 </ sub ambient conditions intermittent electrolysis operating conditions mixed co intermediate co whereas catalysts based catalysts prevent catalyst optimized catalyst catalyst retains x </ type pathway sustainable route surface provides scale conversion results highlight remain oxide pyridine adsorption prolonged operation operando insight Electrocatalytic hydrogenation offers a sustainable route to reductive molecular transformations by generating hydrogen equivalents from water under ambient conditions. However, practical implementation requires earth-abundant heterogeneous electrocatalysts that combine activity, selectivity, and durability under operating conditions. Here, we report a highly selective electrocatalytic hydrogenation of nitrogen-containing aromatic compounds in an anion-exchange membrane electrolyzer using a carbon-supported cobalt catalyst with a finely tuned Co(0)/CoO_<i>x</i> ratio. The optimized catalyst, prepared from CoSO₄·7H₂O and calcined at 750 °C, converts pyridine to piperidine in >99% yield under ambient electrolysis conditions. Ex situ characterization and in situ Co K-edge X-ray absorption spectroscopy revealed that the catalyst retains an intermediate Co(0)/CoO_<i>x</i> ratio under reductive electrolysis conditions, whereas catalysts that become either excessively reduced or remain oxide-rich show lower activity. Kinetic analysis and density functional theory calculations indicate that pyridine hydrogenation proceeds through a Langmuir–Hinshelwood-type pathway, in which the mixed Co(0)/CoO_<i>x</i> surface provides an electronically suitable environment for pyridine adsorption and hydrogenation. This electronically tuned Co(0)/CoO_<i>x</i> surface enables selective hydrogenation of a broad range of nitrogen-containing aromatic compounds, including pyridines, quinolines, pyrazines, nitriles, and nitroarenes, while suppressing undesired hydrogenation pathways observed with Rh-based catalysts. Guided by the operando insight, intermittent electrolysis was introduced to prevent catalyst over-reduction during prolonged operation, enabling gram-scale conversion of pyridine to piperidine in 89% yield with stable cell voltage. These results highlight the importance of maintaining an intermediate Co(0)/CoO_<i>x</i> state for selective electrocatalytic hydrogenation with earth-abundant cobalt catalysts. 2026-09-29T00:00:00Z Text Journal contribution 10.1021/jacs.6c12207.s001 https://figshare.com/articles/journal_contribution/Oxidation-State_Control_of_Cobalt_Electrocatalysts_Enables_Selective_Hydrogenation_of_Nitrogen-Containing_Aromatics/34027575 CC BY-NC 4.0