山东大学：《物理化学》课程教学资源（讲义资料）10.6 Photochemical reaction-2

810. 6 Photochemistry It-class reading Levine, pp. 800-804 photochemistry

§10. 6 Photochemistry Out-class reading: Levine, pp. 800-804 photochemistry

§10.6 Photochemistry 6.5 Quantum yield and energy efficiency Quantum yield or quantum efficiency(p) ForH2+Cl2→2HClΦ=104~10 For h+ Br.->2HBr =0.01 gp>l initiate chain reaction The ratio between the number of moles of reactant consumed or product a=1, product is produced in primary formed for each Einstein of absorbed photochemical process radiation g< l, the physical deactivation is d minar

6.5 Quantum yield and energy efficiency Quantum yield or quantum efficiency (): The ratio between the number of moles of reactant consumed or product formed for each Einstein of absorbed radiation. a n r I   = = For H2+ Cl2→ 2HCl  = 104 ~ 106 For H2+ Br2→ 2HBr  = 0.01  > 1, initiate chain reaction.  = 1, product is produced in primary photochemical process  < 1, the physical deactivation is dominant §10. 6 Photochemistry

§10.6 Photochemistry 6.5 Quantum yield and energy efficiency Photosynthesis: Energy efficiency: 6C0,+6H,O+nhy->CHoE+6O Light energy preserved Total light energy △G=2870 kJ mol For formation of a glucose, 48 light quanta was needed 2870 35.79 48×167.4

Energy efficiency: Photosynthesis: 6CO2 + 6H2O + nh → C6H12O6 + 6O2 rGm = 2870 kJ mol-1 For formation of a glucose, 48 light quanta was needed. 35.7% 48 167.4 2870 =   = 6.5 Quantum yield and energy efficiency §10. 6 Photochemistry

§10.6 Photochemistry 6.6 The way to harness solar energy--photosynthesis 6C02+6H20+ nhy>C6H12 06+602 Porphyrin complex with magnesium Light harvesting protein Photosensitive reaction Reaction initiated by photosensitizer When reactants themselves do not Central chlorophyll eaction cente of reaction center absorb light energy, photosensitizer can be used to initiate the reaction by conversion o of the light energy to the Light harvesting protein reactants Chlorophyll A, B, C, and D

Photosensitive reaction Reaction initiated by photosensitizer. 6CO2 + 6H2O + nh → C6H12O6 + 6O2 When reactants themselves do not absorb light energy, photoensitizer can be used to initiate the reaction by conversion of the light energy to the reactants. Chlorophyll A, B, C, and D Porphyrin complex with magnesium 6.6 The way to harness solar energy—photosynthesis §10. 6 Photochemistry

§10.6 Photochemistry 6.6 The way to harness solar energy Light reaction: the energy content of the light quanta is converted into chemical energy Dark reaction: the chemical energy was used to form glucose 4Fd3++3ADP3-+3P28 4Fd2++ 3ATP4-+0,+Ho+H+ fd is a protein with low molecular weight 3ATP3-+4Fd2+C0,+Ho+H+ 3P2 >(CH2O)+3ADP3+3P2+4Fd3+

Light reaction: the energy content of the light quanta is converted into chemical energy. Dark reaction: the chemical energy was used to form glucose. Fd is a protein with low molecular weight 4Fd3+ + 3ADP3- + 3P2- ⎯→ 4Fd2+ + 3ATP4- + O2 + H2O + H+ 3ATP3-+ 4Fd2++ CO2+ H2O + H+ 3P2- → (CH2O) + 3ADP3- + 3P2- + 4Fd3+ 8h 6.6 The way to harness solar energy §10. 6 Photochemistry

§10.6 Photochemistry 6.6 The way to harness solar energy All the energy on the global surface comes from the sun The total solar energy reached the global surface is 3 x 1024J'y-l, is 10,000 times larger than that consumed by human being 新闻中心国内斯闻 Only 1-2% of the total incident energy 中国玉米亩均单产提高至1227公斤 is recovered for a field of corn 2014年11月21日16:18新华网 21 新华网北京11月21日电者林青、王宇农业部近日组织专家验收,中国农科院作物科 学研究所在新疆生产建设兵团第四师71团万亩玉米示范田实现亩均单产1227.6公斤的新纪录 较2012年创造的11134公斤/亩的全国大面积高产纪录又提高了100多公斤

All the energy on the global surface comes from the sun. The total solar energy reached the global surface is 3  1024 Jy -1 , is 10,000 times larger than that consumed by human being. 6.6 The way to harness solar energy Only 1~2% of the total incident energy is recovered for a field of corn. §10. 6 Photochemistry

§10.6 Photochemistry 6.6 The way to harness solar energy ⑧ Solar-> heating: Solar- >electricity: photovoltaic cell Solar->chemical energ. Photolysis of water photoelectrochemical cell

Solar ⎯→ heating: 6.6 The way to harness solar energy §10. 6 Photochemistry Solar ⎯→ electricity: photovoltaic cell Solar ⎯→ chemical energy photoelectrochemical cell Photolysis of water

§10.6 Photochemistry 6.6 The way to harness solar energy Solar-> heating Solar->electricity: photovoltaic cell photoelectrochemical cell Solar chemical energy g Conducting band p electron gap hole o valence band Photoelectrochemistry and Photolysis

Solar ⎯→ heating: Solar ⎯→ electricity: photovoltaic cell / photoelectrochemical cell Solar ⎯→ chemical energy: 6.6 The way to harness solar energy §10. 6 Photochemistry

§10.6 Photochemistry 6. 6 The way to harness solar energy Photolysis of water/ Photochemical reaction--photocatalysts ?? Photooxidation of organic pollutant S+hy→S S*+R→S++R 4s+2H2O→4s+4H+O2 2R+2H,O→2R+2OH+H, S= Ru(bpy )3 CH3N○><ONCH3 Cl Cl

Photolysis of water/ Photooxidation of organic pollutant Photochemical reaction—photocatalysts ?? S + h → S * S * + R → S + + R- 4S + + 2H2O → 4S + 4H+ + O2 2R-+ 2H2O → 2R + 2OH-+ H2 S = Ru(bpy)3 2+ 6.6 The way to harness solar energy §10. 6 Photochemistry

§10.6 Photochemistry 6. 6 The way to harness solar energy Photolysis of water based on semiconductors T1O the most important photocatalyst Modification of TiO2 Large band gap (>3.0eV) Visible-light-driven photocatalysts S, TO A) Zno Unsuitable \B levels for water oidation H=7 Unsuitable CB level

Photolysis of water based on semiconductors 6.6 The way to harness solar energy TiO2 the most important photocatalyst. Modification of TiO2 . §10. 6 Photochemistry