Question

calculate the overpotential for the reduction of Ni a) at a current density of 300 A/m2 at a nickel cathode in a solution containing 1 M Ni2. Assume that the high-field approximation to the Butler-Volmer equation can be used and that 2 x 10 A/m2 is the exchange current density for this reaction. ions b) Calculate the potential of the cathode assuming initially that the only reaction is the reduction of nickel ions. e) Calculate the current due to the reduction of H at the cathode potential derived in (b) for a solution pH 3. You can assume that the exchange current density for hydrogen evolution of 1 x 103 A/m2 is proportional to the square root of the proton activity and that the high-field approximation can be used d) Calculate the current efficiency for the deposition of nickel at pH 3 and 300 A/m2

Answer 1

B=0.9 B=0.7 B=0.5 Y = i/i. = 0.3 When B differs from 0.5 the i vs n curve becomes asymmetrical. -80 - B=0.1 -100 6 4 2 2 4 0 =Fn/RT

Tafel Plot General BV Equation a=a=0.5 iº=1.0x104A Ini = lni, - af Ini Ini, + DTT 10 !!! = h TTTT 001 - -10 -8 -6 4 -2 0 2 4 6 8 10 O = Fn/RT dn b= dn d logi d logi

>05 - Ni?' +90 Nies ; 9V - I mele of electronsa i frakowy (F): 9.65*10%€ - Spontaneity of Realou flachyons under conditions dihet 'than Standard State - Concentrations of rell species opgeet Eceti cous = lm; Pgare I am. E cel Dlous) 71.14; Paasei = I am: Eiels Cpotential changes) -Cell potential pirops as the reactands are consumed aucl the teachrov approaches equilibrary. - AG = -nftan". La Butler -Volumer Equations - Tone A (ke) (ka Cela - Overpotenhal n = 40-Adeg -i-io [emanfor errainful a a Tafel plots - very small n Do-limfries & Bezi e7/06 - very layen negativen, i = lo earth positive a, ia lecranth from the plot , eo (c) & A can be determined 9:05 05

Ovenpotential apruedd gorcmane zawlibre poloha whereas, equilibrium potential in the modunanje potens isi 2010-2 Atma na = RT 1=2, 7=298 K, f: 96500 c/neole 1 R= 8.31 J/mole.K. Over potential n=104 104 mV = 0.104V - 1 = 2x10 3 Alma (6) Calculation for ß. B-1-en ( t h $21.0032 (%. ic = is emp (BRT Jemp-05! * 96500x40-104) 8.31x298 la ooons Alma? (d) Centa icini x 100 liit lett

ah Home Over S almon te=0.572. Erilah : 3pii 2-0.059 ug the --0084x3 -0.181 Name =Ve- Earth =-0.96-(-0.18) = -0.78V 80.5, i = (x103 Alm? . Vithil i 10 eup (-0.5 x 1 2 3 x 298 her dem; theith - 300+ 33.35 = 333.3526 Alma CENN x100 écrit leita No.5 x 1 x965rox! 300 333.3526 CEN= 89.99% Current efficiency (CE) is always defined with respect to the reachon og interest, which is the deposition aal. Hence si electrowinning & not of current efficiency of H₂ evolution,