能量密度 Chemical bonds are an excellent form of energy storage! diesel Solar Fuels? 35 gasoline 受=o propane 25 ethanol 20 RossIFuels cogE> 15 F pumped hydro capacitors 10 liquefied natural gas liquid H (DOE goal) compressed air compressed H, gas (700 bar) i ion battery H, gas (STP) 10 20 30 40 Mass energy density, M/kg 140
1 能量密度
太阳能:120000TW 120,000 TW(600 TW practical) Energy CO, Production Consumption Billion metric Tons Terawatts 2010 17.0TW 2030 22.7TW 40 "International Energy outlook 2009, Energy Information Administration. United States Department of Energy http://www.eia.doe.gov/oiaf/ieolemissions.html Basic Research Needs To Assure A Secure Energy Future, Basic Energy Sciences Advisory Committee, United States Department of Energy.http://www.er.doe.gov/bes/reports/files/sef_rptpdf http://www.wallpapers-free.org/12/-/sunEarth Challenge: intermittent supply requires storage to buffer delivery http://www.renewablepowemews.com/wp- http://www.sonyinsider.com/wp- nttp //cache gawkerassets com/assets/images content/uploads/2009 08/PIAD001000823-450x384. pg 8/201 1/05/grid jpg
2 太阳能：120,000 TW
太阳能转为燃料的方式 Photobiologic >engineered Photochemical>metallorganic organisms that synthesize fuels absorbers and redox mediators EDTA Ru(hpy)y H EDTA Ru(hpy H2 NREL Fig 3. Scheme for the photochemical generation of hydrogen in a reduction half reaction Solar thermal heterogeneous catalysis Solar electricity, water-splitting 11 MW near Seville Today these technologies cannot compete with fossil fuels 面 3
3 太阳能转为燃料的方式
利用太阳能进行电解水制氢(人工光合作用) Catalyst Solar energy H2O 2()+ 2 主要设计思路: Scheme 1: Photovoltaic electrolysis (PV-E Scheme 2: Photoelectrochemical (PEC) water splitting Renewable Fu CO -free energy source Electro- Combustion reduction OFR HER ≥CO2 Independent pv modules Single, fully integrated unit Drive separate electrolyzer Absorbs sunlight and produces units to produce H2 /0 H,/O 2
4 利用太阳能进行电解水制氢（人工光合作用） Solar energy + H2O H2 (fuel) + O2 Catalyst 主要设计思路：
光催化分解水与电解水制氢 Photosynthesis Plant 水还原(析氢,HER) g CO2+ H2o Chemical 4H2O+4e→40H+2H2 energy E F meta 1.23e∨ Artificial Photosynthesis 40H+4h+→2H2+O2 (Water splitting) H2+O2 水氧化(析氧, OER) Chemical energy H2O △G0=237kJ/mol Semiconductor Electro/ Metal electrode ◆分解水是耗能过程,能源可以来自电、太阳能(光、热)、风能等 ◆由析氢反应(HER)和析氧反应(OER)两个半反应组成,其中OER是 4电子过程,反应动力学较慢,是分解水过程中的决速步骤 5
5 光催化分解水与电解水制氢 水还原（析氢，HER） 水氧化（析氧， OER） ◆ 分解水是耗能过程，能源可以来自电、太阳能（光、热）、风能等 ◆ 由析氢反应（HER）和析氧反应（OER）两个半反应组成，其中OER是 4电子过程，反应动力学较慢，是分解水过程中的决速步骤
电解水制氢(及其氢氧燃料电池)的化学半反应 current density 2H2→O2+4H+4e H2→2H+2e diffusion- Ruo platinum limited Ps‖ hydrogenase current 0 123 E(vS RHE) PtNi diffusion laccase overpotential limited current O2+4H+4e→2H2O 2H++2e→H2 Ref: M.T. M. Koper, H.A. Heering, in"Fuel Cell Science", Eds. A. Wieckowski, J.K. Norskov, Wiley, (2010) p.71-110
6 电解水制氢（及其氢氧燃料电池）的化学半反应 Ref: M.T.M. Koper, H.A. Heering, in "Fuel Cell Science", Eds. A. Wieckowski, J.K. Norskov, Wiley, (2010), p.71-110
过电势与电催化剂 Mn Oxide oER: Ir/C-20wt 6 Ru/-.% EH (1.23 0.20 EⅣvs.RHE E/(RHE) Acid Base Precious Non-precious Precious Non-precious metals metals metals metals High TOF Medium TOF Medium-High TOF Medium TOF evolution catalysts Pt metal sulfides Pt metal alloys, metal phosphides e.g. NiMo Low TOF Low TOF LOw TOF evolution No known catalysts IrO, RuO, candidates RuO Ni-Fe-Co-0. and other oxide alloys
7 过电势与电催化剂
太阳光转化效率的计算? Photovoltaic efficiency? Solar fuels, 'efficiency can be defined in many ways One must be cautious when interpreting the literature, as some definitions of efficiency( % ) do not reflect how efficiently a device would produce fuels from sunlight in commercial applications Two general types of efficiency definitions The one true indicator of device performance: Solar-to-fuel efficiency (STF),e.g. solar-to-hydrogen(STH Diagnostic efficiencies Provides information to the researcher one the fundamental physical and chemical workings of the device. a high efficiency for these measurements does not necessarily translate to high STF/STH efficiency Applied bias photon-to-current efficiency (aBpe) External quantum efficiency (EQe)= incident photon-to-current efficiency(IPCe) Internal quantum efficiency (IQE)=absorbed photon-to-current efficiency(APCE 8
8 太阳光转化效率的计算？
太阳光转化为燃料(STF)的效率计算 Fuel O, chemical energy Summed over Rate at which each within each fuel Panel all fuels fuel is produced (H, or MeOH) CO, H,o Power Efficienc Power Out Rate ofchemical energy production 2i(h Second )(AGi I mol Power In Power input from solar energy (Ptotal2)(Area cm2) e.g. AM1.5 solar radiation Insolated area of (100mW/cm2) the device 9
9 太阳光转化为燃料（STF）的效率计算
太阳光谱能量 2hv+H2O→为O2gs)+H2 hv≥123eV PHOTON ENERGY[eⅥ 503.02.0 0.5 1.5 1.23eV Bak et. al, Int J. Hydrogen Energy vo|27(2002)9911022 乙zF 0.5 umm> 0.0 0.5 2.0 3.0 WAVELENGTH m 10
10 太阳光谱能量