KOH : ; 30 wt. % KOH, %, Na 3 PO 4. ,. 40 g/ L Na 2 CO 3 25 g/ L Na 3 PO 4, 100 ma/ cm 2. 3 mol/ L H 2 SO 4.

Transcription

1 EL ECTROCHEMISTR Y Vol 4 No 4 Nov 1998 KOH ( ) wt % KOH Ni i 0, Tafel b, 1 :40,40, Tafel 120 mv, Ea kj/ mol, 40, mv kj/ mol (5 / 5 T) 1 lg i,, : ;,,,, : ( 70 ), (OER),, KOH, - -, 30 wt %KOH %, ( 800 # ) 40 gl Na 3 PO 4,,, 40 g/ L Na 2 CO 3 25 g/ L Na 3 PO 4, 100 ma/ cm 2, 3 mol/ L H 2 SO wt % KOH, Hg/ HgO, , ; 3 3

2 4 : KOH ,, 0 5 A/ cm 2, A/ cm 2 1 h J H2C, 501, Solartron1287 S wt % KOH, 2 Fig 1 Anodic polarization curves of Ni electrode in 30 wt % KOH solution at different temper2 2 1 atures , 30 wt % KOH [ 1 ],,,, Tafel ; Tafel b, i wt % KOH Tab 1 The kinetic parameters for OER on Ni electrode in 30 wt % KOH at the temperatures between / b/ mv i 0 / 10-7 ma cm - 2 b/ mv i 0 / ma cm

3 , 40, i 0 b, [3 4 ] : OH - Ζ OH ads + e - OH ads + OH - Ζ O - ads + H 2 O O - ads + 2NiOOH Ζ 2NiO 2 + H 2 O + e - NiO 2 + OH ads Ζ NiOOH + O ads 2O ads Ζ O 2 : KOH NiOOH [4 5 ] 1 40,, : OH ads O ads -, OH - OH - i _ 1 = k 1 (1-2 ) [OH - ]exp ( F/ R T) (1) i χ 1 = k 1 exp ( - F/ R T) k 2 [OH - ] = k - 2 [ H 2 O ] (3) i 3 = k 3 exp ( F/ R T) (4) _ i χ i 1 = i 3, : i A = 4 k 3 exp ( F/ R T) 0 5, (1) - (4) : - 1 = 1 + k - 2[ H 2 O ] k 2 [OH - ] 1 + = k 1 k 2 [OH - ] 2 F exp k - 1 k - 2 [ H 2 O ] R T k F k 1 [ O H - exp ( ] 3 R T ) + k 3 k 1 [OH - ] [2 ], (2), Tafel b = R T/ (1 + ) 1 F, mv ; = 1 + k - 1-2[ H 2 O ] k 2 [OH - ] + k 3 k 1 [ O H - 00, Tafel ] b = R T/ F, mv, mv,, (barrier2effect) [6 ] 45, Tafel 70 mv, 40, Ni ( ), 2 2 E a, M H Miles [7 ], lg i 0 1/ T, : E a = R 5log i 0 5 (1/ T)

4 4 : KOH (A) (B),Ni - lg i 0 1/ T Fig 2 Plots of - lg i 0 vs 1/ T at lower overpotentials below 45 (A) and above 45 (B) for OER on Ni electrode 2 45 (A) (B), - lg i 0 1/ T :22 40 E a = kj / mol,45 60 E a = kj / mol,, - lg i 0 1/ T,, (45 ) E a kj / mol ( R = 0 952), 2 3, 3 T, ( i = 70 ma/ cm 2 ), Fig 3 Plot of vs T for the OER on Ni elec2, 3 2 trode at 70 ma/ cm 2, (5 / 5 ) i - (5 / 5 ) i,,, (,

5 ,, ) - (5 / 5 ) i, :,, - (5 / 5 ) i,,,, 2 T Tab 2 Relationship between OE overpotential and temperature T for OER on Ni electrode / ma cm T T T T T T T T T T lg i - (5 / 5 ) i, ( 40 ) : wt % KOH Tafel, 40 : 40, , 40, Tefel mv, mv kj / mol - (5 / 5 ) i lg i kj / mol Fig 4 Plots of - (5 / 5 ) i lg i at high, overpotentials for OER on Ni elec2 : - (5 / 5 ) i lg i 40 trode,40, - (5 / 5 ) i lg i 4 63,

6 4 : KOH 433 Oxygen Evolution Behavour on Ni Electrode in KO H Solution Cao Xiaoyan 3 3 Yuan Huatang Zhou Zuoxiang 3 Zhang Yunshi ( Inst of New Energy M aterial Chem N ankai U niv Tianjin ) Abstract The steady- state polarization curves of oxygen evolution were measured at temperatures between on Ni electrode in 30 wt % KOH solution by galvanostat meth2 ode The exchange current densities, Tafel slopes and t ransfer coefficient s were st udied It was found that 40 is a special temperature, near which the kinetic parameters change abrupdy The Tafel slopes for oxygen evolution reactions at higher overpotentials change f rom more t han 120 mv to about 70 mv when the temperature raises to from Simultaneously, the heat of activation is changes from kj / mol to kj / mol Moreover, the - (5 / 5 ) i and how it changes with lg i are quite different in the two temperature ranges : The slope of - (5 / 5 ) i vs lg i is 4 63 at the lower temperatures, while at the higher temperatures it is only Key words Nickel electrode, Oxygen evolution reaction, Steady- state polarization Reference s 1 Balej J Determination of the oxygen and hydrogen overvoltage in concenttrated alkali hydroixde solutions Int J Hydrogen Energy, 1985, 10 (6) : Bronoel G, Reby J Mechanism of oxygen evolution in basic medium at a nickel electrode Electrochimica Acta, 1980, 25 : Miao H J, Piron D L Electrodeposition of catalytically active nickel for oxygen evolution reaction2effects of an2 odic composition The Can J Chem Eng, 1993, 71 : Tu P W T, Srinivasan S Electrochemical2Ellipsometric studies of oxide film formed on nickel during oxygen evolution J Electrochem Soc, 1978, 125(9) : ,,1994,33 (6) :685 6 Meyer R E Cathodic processes on passive zirconium J Electrochem Soc, 1960, 107 : Miles M H, Kissel S et al Effect of temperature on electrode kinetic parameters for hydrogen and oxygen evolu2 tion reactions on nickel electrodes in alkaline solutions J Electrochem Soc, 1976, 123(3) : 332