Comprehending the mechanistic involvement of a support-catalyst interface is critical for effective design of industrially relevant electrocatalytic processes such as the alkaline hydrogen evolution reaction (alHER). The understanding of the kinetically sluggish alHER exhibited by both Pt and Pt-group-metal-free catalysts is primarily derived from indirect electrochemical parameters such as the Tafel slope. To address these issues, we establish the critical role of a nanocarbon floret (NCF) based electrochemical support in generating a key cobalt-oxohydroxo (OH-CoO) intermediate during the alHER through operando Raman spectro-electrochemistry. Specifically, interfacial nano-engineering of a newly designed carbon support (NCF) with a spinel Co3O4 nanocube catalyst is demonstrated to achieve a facile alHER (-0.46 V@10 mA cm(-2)). Such an efficient alHER is mainly attributed to the unique lamellar morphology with a high mesoporous surface area (936 m(2) g(-1)) of the NCF which catalyses the rate-determining water dissociation step and facilitates rapid ion diffusion. The dissociated water drives the formation of the OH-CoO intermediate, spectroscopically captured for the first time through the emergence of a nu OH-CoO Raman peak (1074 cm(-1)). The subsequent alHER proceeds through the Volmer-Heyrovsky route (119 mV dec(-1)) via the T-d Co2+ Co3+ Co4+ oxidative pathway. Concomitant graphitization of the NCF through the disappearance of nu sp(3)C-H (2946 cm(-1)) supports the co-operative dynamics at the Co3O4-NCF interface. Thus, the NCF positively contributes towards the lowering of the overpotential with a low charge-transfer resistance (R-ct = 35.8 omega) and high double layer capacitance (C-dl = 410 mF cm(-2)).
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