首页|Morphology and valence state evolution of Cu:Unraveling the impact on nitric oxide electroreduction
Morphology and valence state evolution of Cu:Unraveling the impact on nitric oxide electroreduction
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Ammonia(NH3)serves as a critical component in the fertilizer industry and fume gas denitrification.However,the conventional NH3 production process,namely the Haber-Bosch process,leads to consider-able energy consumption and waste gas emissions.To address this,electrocatalytic nitric oxide reductionreaction(NORR)has emerged as a promising strategy to bridge NH3 consumption to NH3 production,har-nessing renewable electricity for a sustainable future.Copper(Cu)stands out as a prominent electrocat-alyst for NO reduction,given its exceptional NH3 yield and selectivity.However,a crucial aspect that remains insufficiently explored is the effects of morphology and valence states of Cu on the NORR perfor-mance.In this investigation,we synthesized CuO nanowires(CuO-NF)and Cu nanocubes(Cu-NF)as cath-odes through an in situ growth method.Remarkably,CuO-NF exhibited an impressive NH3 yield of 0.50+0.02 mg cm-2 h-1 at-0.6 V vs.reversible hydrogen electrode(RHE)with faradaic efficiency of 29.68％+1.35％,surpassing that of Cu-NF(0.17+0.01 mg cm-2 h-1,16.18％±1.40％).Throughout the elec-troreduction process,secondary cubes were generated on the CuO-NF surface,preserving their nanosheet cluster morphology,sustained by an abundant supply of subsurface oxygen(s-O)even after an extended duration of 10 h,until s-O depletion ensued.Conversely,Cu-NF exhibited inadequate s-O content,leading to rapid crystal collapse within the same timeframe.The distinctive current-potential relationship,akin to a volcano-type curve,was attributed to distinct NO hydrogenation mechanisms.Further Tafel analysis revealed the exchange current density(i0)and standard heterogeneous rate constant(k0)for CuO-NF,yielding 3.44 × 10-6 A cm-2 and 3.77 × 10-6 cm-2 s-1 when NORR was driven by overpotentials.These findings revealed the potential of CuO-NF for NO reduction and provided insights into the intricate interplay between crystal morphology,valence states,and electrochemical performance.
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