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Recent progress on advanced design for photoelectrochemical reduction of CO2 to fuels

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  • ReceivedSep 28, 2017
  • AcceptedOct 26, 2017
  • PublishedJan 31, 2018

Abstract


Funded by

This work was financially supported in part by the National Key R&D Program of China(2017YFA0207301)

973 Program(2014CB848900)

and the Fundamental Research Funds for the Central Universities(WK2060190064)

the National Natural Science Foundation of China(21471141,U1532135)

the CAS Key Research Program of Frontier Sciences(QYZDB-SSW-SLH018)

the CAS Interdisciplinary Innovation Team

the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology(2016FXCX003)

Recruitment Program of Global Experts

the CAS Hundred Talent Program

Anhui Provincial Natural Science Foundation(1708085QB26)

China Postdoctoral Science Foundation(BH2060000034)


Acknowledgment

This work was financially supported in part by the National Key R&D Program of China (2017YFA0207301), the National Basic Research Program of China (973 Program, 2014CB848900), the National Natural Science Foundation of China (21471141 and U1532135), the CAS Key Research Program of Frontier Sciences (QYZDB-SSW-SLH018), the CAS Interdisciplinary Innovation Team, the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology (2016FXCX003), the Recruitment Program of Global Experts, the CAS Hundred Talent Program, Anhui Provincial Natural Science Foundation (1708085QB26), China Postdoctoral Science Foundation (BH2060000034), and the Fundamental Research Funds for the Central Universities (WK2060190064).


Interest statement

The authors declare that they have no conflict of interest.


Contributions statement

Zhang N prepared the figures and wrote the paper. Xiong Y proposed and guided the project. Gao C, Long R, and Xiong Y revised the manuscript. All authors joined the discussion and gave useful suggestions.


Author information

Ning Zhang received his BSc in chemistry in 2013 from the University of Science and Technology of China (USTC). Since then he has been studying as a PhD candidate under the tutelage of Professor Yujie Xiong at USTC. His research interests focus on the controlled synthesis of semiconductors and their applications of photocatalysis and photoelectrocatalysis.


Ran Long received her BSc in chemistry in 2009 and PhD in inorganic chemistry under the tutelage of Professor Yujie Xiong in 2014, both from USTC. She is currently a research associate professor at USTC. Her research interests focus on the controlled synthesis and catalytic applications of metal nanocrystals.


Chao Gao received his BSc in chemistry in 2010 from Anhui Normal University, and PhD in inorganic chemistry in 2015 (with Professors Xingjiu Huang and Zhiyong Tang) from USTC. During his PhD research, he had two-year training (2013–2015) with Professor Zhiyong Tang at the National Center for Nanoscience and Technology (NCNST). He is now working as a postdoctoral research fellow with Professor Yujie Xiong at USTC. His current research interests are focused on the design and synthesis of photocatalysts and photoelectrodes for CO2 reduction.


Yujie Xiong received his BSc in chemical physics in 2000 and PhD in inorganic chemistry under the tutelage of Professor Yi Xie in 2004, both from USTC. After four-year training with Professors Younan Xia and John A. Rogers, he joined the National Nanotechnology Infrastructure Network (NSF-NNIN), and served as the Principal Scientist and Lab Manager at Washington University in St. Louis. In 2011, he moved to USTC to take the position of professor of chemistry. His research interests include the synthesis, fabrication and assembly of inorganic materials for energy and environmental applications.


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  • Figure 1

    Schematic diagrams for PEC CO2 reduction in water using semiconductor as (a) photocathode, (b) photoanode and (c) both photoanode and photocathode. (d) Schematic diagram for the device combining a photovoltaic cell with an efficient electrochemical catalyst for CO2 reduction.

  • Figure 2

    Conduction band and valence band potentials of several typical semiconductors relative to the standard redox potentials of CO2 reduction in water at pH 7.

  • Figure 3

    Two proposed mechanisms for CO2 reduction to methane: (a) formaldehyde pathway and (b) carbene pathway. Reproduced with permission from Ref. [14]. Copyright 2013, Wiley-VCH Verlag GmbH & Co.

  • Figure 4

    (a) Schematic illustration and (b) SEM image of Sn-coupled p-Si nanowire arrays. (c) Comparison of products and FEs with various p-Si photocathodes. Adapted with permission from Ref. [29]. Copyright 2014, Wiley-VCH Verlag GmbH & Co. (d) Schematic illustration and (e) SEM image of Zn/ZnO/ZnTe structure. (f) The amount of produced CO under different potentials (vs. RHE) with Zn/ZnO/ZnTe structure as a photocathode. Adapted with permission from Ref. [37]. Copyright 2014, Wiley-VCH Verlag GmbH & Co.

  • Figure 5

    (a) Electrochemical impedance spectroscopy of Co-doped MoS2, CoS2, MoS2 and CoS2/MoS2 samples. (b) Mechanism of PEC CO2 reduction on the Co-doped MoS2 NPs. (c) Time-dependent curve of methanol yields with Co-doped MoS2 and CoS2/MoS2 samples. Adapted with permission from Ref. [96]. Copyright 2015, Elsevier. (d) Mott-Schottky plot and (e) band potential diagram of B-doped g-C3N4 (BCN1.5) and (f) photocurrent responses for CO2 reduction by various B-doped g-C3N4 samples. Adapted with permission from Ref. [41]. Copyright 2016, Elsevier.

  • Figure 6

    Schematic diagrams for (a) type-II structure heterojunction and (b) photocathode components.

  • Figure 7

    (a) SEM image and (b) Chrono potentiometric measurements at a constant current density of 1.67 mA cm−2 for Cu/Cu2O/CuO nanowires photocathode. Reproduced with permission from Ref. [105]. Copyright 2014, the Royal Society of Chemistry. (c) SEM image of CuFeO2/CuO mixed film. (d) Photocurrent response and PEC formate production for CuFeO2/CuO mixed film. Reproduced with permission from Ref. [40]. Copyright 2015, the Royal Society of Chemistry. (e) Schematic diagram for the TiO2 passivated p-GaP photocathode. (f) Photocatalytic current-potential curves of p-GaP photocathodes with different TiO2 thicknesses. Adapted with permission from Ref. [38]. Copyright 2014, the American Chemical Society.

  • Figure 8

    Schematic illustration for (a) the Schottky junction between metal and p-type semiconductor and (b) the charge migration in photocatalytic process. (c) Schematic illustration for the charge migration in the photocathode anchored with metal nanoparticles under light illumination.

  • Figure 9

    Periodic table depicting the primary reduction products from the reaction system of CO2 and H2O on metal and carbon electrodes. Adapted with permission from Ref. [13]. Copyright 2015, the American Chemical Society.

  • Figure 10

    (a) The results of PEC CO2 reduction with bare and metal-decorated CuO/Cu2O films as photocathodes. Reprinted with permission from Ref. [75]. Copyright 2014, Elsevier. (b) Photocurrent response, (c) IPCE values and (d) FEs of CO and H2 from the PEC CO2 reduction with ZnTe/ZnO (A) and Au-coupled ZnTe/ZnO (B) photocathodes. Reproduced with permission from Ref. [36]. Copyright 2015, the Royal Society of Chemistry.

  • Figure 11

    The molecular structures of (a) Re(bipy)(CO)3X, (b) [Ru(dcbpy)2(CO)2]2+ and (c) Ru(II)-Re(I) binuclear complex. (d) Proposed mechanism for CO2 reduction to CO using Re(bipy)(CO)3X as a catalyst.

  • Figure 12

    Schematic representations for (a) Re(bipy)(CO)3Cl complex covalently bound to TiO2-modified Cu2O, (b) Ru(II)-Re(I) supramolecular modified NiO, and (c) molecular Mn catalyst-immobilized mesoporous TiO2 photocathode for CO2 reduction. Adapted with permission from Ref. [33], copyright 2016, the American Chemical Society, Ref. [134], copyright 2015, the Royal Society of Chemistry, and Ref. [140], copyright 2016, Wiley-VCH Verlag GmbH & Co, respectively.

  • Figure 13

    (a) Possible intermediates during the electrochemical reduction of pyridine. Adapted with permission from Ref. [147]. Copyright 2013, the Royal Society of Chemistry. (b) Some reported intermediates involved in the pathway of CO2 reduction. (c) Reduction of CO2 to methanol by a 1,2-dihydropyridine intermediate species via hydride and proton transfer steps. Adapted with permission from Ref. [153]. Copyright 2014, the American Chemical Society.

  • Figure 13

    (a) Possible intermediates during the electrochemical reduction of pyridine. Adapted with permission from Ref. [147]. Copyright 2013, the Royal Society of Chemistry. (b) Some reported intermediates involved in the pathway of CO2 reduction. (c) Reduction of CO2 to methanol by a 1,2-dihydropyridine intermediate species via hydride and proton transfer steps. Adapted with permission from Ref. [153]. Copyright 2014, the American Chemical Society.

  • Figure 14

    Schematic illustration for (a) a CODH functionalized dye-sensitized p-NiO photocathode for selective CO2 reduction to CO and (b) a PEC enzyme-cascade system containing a Rh complex and three dehydrogenases for CO2 reduction to CH3OH. Adapted with permission from Ref. [32], copyright 2014, the American Chemical Society, and Ref. [165], copyright 2017, Wiley-VCH Verlag GmbH & Co, respectively.

  • Figure 15

    (a) Schematic diagram and (b) chemical generation rates of various products for the PEC setup that combines Pt-modified TiO2 nanotubes as photoanode and Pt-modified rGO as dark cathode for CO2 reduction. Adapted with permission from Ref. [169]. Copyright 2014, the American Chemical Society. (c) Schematic representation and (d) product distribution for the PEC system of CO2 reduction that utilizes a WO3 photoanode and Cu or Sn/SnOx cathode under visible-light irradiation. Adapted with permission from Ref. [44]. Copyright 2014, the Royal Society of Chemistry.

  • Figure 16

    (a) Schematic illustrating the Z-scheme system for CO2 reduction. Adapted with permission from Ref. [45]. Copyright 2011, the American Chemical Society. (b) Schematic illustration for the PEC setup with Z-scheme configuration consisting of Ru(II)-Re(I) metal complex modified p-NiO photocathode and CoOx/TaON photoanode for CO2 reduction to CO. Reproduced with permission from Ref. [46]. Copyright 2016, the American Chemical Society.

  • Figure 17

    The generalized current density-voltage (J-V) diagram of a directly coupled photovoltaic-electrochemical device graphically which identifies the power flows relative to total incident solar power. Adapted with permission from Ref. [185]. Copyright 2013, the National Academy of Sciences.

  • Figure 18

    (a) Schematic illustration for the solar-driven CO2 reduction device. (b) Photovoltaic and electrocatalytic current density-voltage behaviors. (c) Selectivity toward CO, solar current density and solar-to-CO efficiency as a function of photoelectrolysis time. Reproduced with permission from Ref. [48]. Copyright 2017, Nature Publishing Group.

  • Figure 19

    (a) Schematic representation for the electron and proton transport in wireless monolithic device for CO2 reduction. (b) Schematic illustration for the r-STO/InP/[RuCP] wireless device for CO2 reduction. Adapted with permission from Ref. [132]. Copyright 2013, the Royal Society of Chemistry.

  • Table 1   Thermodynamic reactions of CO reduction

    Equation

    Reaction

    ΔH0

    (kJ mol−1)

    ΔG0

    (kJ mol−1)

    ΔE0

    (V)

    1

    CO2(g) → CO(g) + 1/2O2(g)

    283

    257

    1.33

    2

    CO2(g) + H2O(l) → HCOOH(l) + 1/2O2(g)

    270

    286

    1.48

    3

    CO2(g) + H2O(l) → HCHO(l) + O2(g)

    563

    522

    1.35

    4

    CO2(g) + 2H2O(l) → CH3OH(l) + 3/2O2(g)

    727

    703

    1.21

    5

    CO2(g) + 2H2O(l) → CH4(g) + 2O2(g)

    890

    818

    1.06

    6

    H2O(l) → H2(g) + 1/2O2(g)

    286

    237

    1.23

  • Table 2   The thermodynamic potentials the normal hydrogen electrode (NHE) at pH 7 for various CO reduction products and water splitting

    Equation

    Products

    Reaction

    ΔE0 (V)

    vs. NHE at pH 7

    7

    CO2•− intermediate

    CO2 + e → CO2•−

    −1.9

    8

    Carbon monoxide

    CO2 + 2H+ + 2e → CO + H2O

    −0.53

    9

    Formic acid

    CO2 + 2H+ + 2e → HCOOH

    −0.61

    10

    Formaldehyde

    CO2 + 4H+ + 4e → HCHO + H2O

    −0.48

    11

    Methanol

    CO2 + 6H+ + 6e → CH3OH + H2O

    −0.38

    12

    Methane

    CO2 + 8H+ + 8e → CH4 + 2H2O

    −0.21

    13

    Hydrogen

    2H+ + 2e → H2

    −0.41

    14

    Oxygen

    H2O + 2h+ → 1/2O2 + 2H+

    0.82

  • Table 3   Some recently developed advances of photocathodes for PEC CO reduction

    Photocathode

    Condition

    Main products

    Efficiency

    Ref.

    Designing nanostructures for photocathodes

     

    p-Si nanowire arrays

    KHCO3 (0.1 mol L−1), −1.5 V vs. SCE, AM 1.5G light (100 mW cm−2), 3 h

    CO, formate

    4.3 μmol, FE: 7.3% 4.7 μmol, FE: 7.8%

    [29]

    CuO-Cu2O nanorod arrays

    CO2-saturated Na2SO4 (0.1 mol L−1), −0.2 V vs. SHE, AM 1.5G light, 90 min

    CH3OH

    ca. 85 mmol L−1, FE: 94–96%

    [82]

    Cu-decorated Co3O4 nanotube arrays

    CO2-saturated Na2SO4 (0.1 mol L−1), −0.9 V vs. SCE, visible light, 8 h

    Formate

    6.75 mmol L−1 cm−2, select.: close to 100%

    [76]

    ZnTe coated Zn/ZnO nanowires

    KHCO3 (0.5 mol L−1), −0.7 V vs. RHE, >420 nm(490 mW cm–2),1 h

    CO

    ca.70 mmol cm−1, FE: 22.9%

    [37]

    ZnTe/ZnO nanowire arrays

    KHCO3 (0.5 mol L−1), −0.7 V vs. RHE, AM 1.5G light, 3 h

    CO

    10.3 μmol cm–2, FE: 7.2% select.: 8.7%

    [36]

    Polycrystalline Mg-doped CuFeO2

    NaHCO3 (0.1 mol L−1, pH=6.8), −0.9 V vs. SCE, LED source (470 nm), 8–24 h

    Formate

    FE: 10%

    [95]

    Co-doped MoS2 nanoparticles

    KHCO3 (0.1 mol L−1, pH=9), −0.9 V vs. SCE, ≥420 nm(100 mW cm−2),350 min

    CH3OH

    35 mmol L−1

    [96]

    Boron-doped g-C3N4 films

    NaHCO3 (0.5 mol L−1, pH=7.3), −0.4 V vs. Ag/AgCl, AM 1.5G light (100 mW cm−2)

    C2H5OH

    5-times larger for photocurrent FE: 78%

    [41]

    CuO nanowires/Cu2O/Cu foil

    KHCO3 (0.1 mol L−1, pH=6.8), −0.6 V vs. RHE, AM1.5 G light, 10 min

    CO + HCOOH

    1.67 mA cm−2, select.: 60%

    [105]

    CuFeO2/CuO mixed catalyst

    KHCO3 (0.1 mol L−1), no external bias, AM 1.5G light (100 mW cm−2)

    Formate

    5 μmol h−1, select.: 90%, energy efficiency: ~1%

    [40]

    10 nm TiO2-passivated p-GaP

    NaCl (0.5 mol L−1)+pyridine (10 mmol L–1), −0.5 V vs. overpotential, green laser (532 nm), 8 h

    CH3OH

    0.5 V shift of overpotential 4.9 μmol, FE: 55%

    [38]

    Anchoring cocatalysts on photocathodes

     

    Sn-coupled p-Si nanowire arrays

    KHCO3 (0.1 mol L−1), −1.5 V vs. SCE, AM 1.5G (100 mW cm−2), 3 h

    CO, formate

    9.8 μmol, FE: 23.0%; 19.5 μmol, FE: 45.5%

    [29]

    Pb-deposited CuO/Cu2O film

    KHCO3 (0.1 mol L−1), −0.4 V vs. SCE, visible light, 1 h

    HCOOH, CH3OH, CO

    0.524 μmol h−1 cm−2, FE: 19.32%0.102 μmol h−1 cm−2, FE: 11.33%0.243 μmol h−1 cm−2, FE: 9.80%

    [75]

    Au-coupled ZnTe/ZnO nanowire arrays

    KHCO3 (0.5 mol L−1), −0.7 V vs. RHE, AM 1.5G light, 3 h

    CO

    112.0 μmol cm−2, FE: 58.0% Select.: 64.9%

    [36]

    Re(bipy–tBu)(CO)3Cl+p-Si

    CH3CN/water mixtures, −1.9 V vs. Fc/Fc+, 661 nm,2.5 h

    Syngas (H2:CO=2:1)

    5.6 mA cm−2, FE: 102%

    [130]

    ZnDMCPP–Re(bpy)(NHAc) complex sensitized p-NiO

    Bu4NBF4 in DMF solution, Ag/AgNO3 reference, visible light, 5 min

    CO

    0.93 μmol, FE: 6.3%

    [70]

    Re(bipy–tBu)(CO)3Cl paired TiO2-protected Cu2O

    Bu4NBF4 (0.1 mol L−1) and CH3OH (1 mol L−1) in CH3CN, −1.73 V vs. Fc/Fc+, AM 1.5G light, 5.5 h

    CO

    1.5 mA cm−2, FE: 100%

    [110]

    Re(bipy–tBu)(CO)3Cl immobilized mesoporous-TiO2-modified Cu2O

    Bu4NBF4 (0.1 mol L−1) in CH3CN, −2.05 V vs. Fc/Fc+, AM 1.5G light, 1.5 h

    CO

    FE: 80–95%

    [33]

    [Ru(L-L)(CO)2]n polymer modified Zn-doped p-InP

    CO2-saturated water, −0.6 V vs. Ag/AgCl, 400<λ<800 nm, 3 h

    Formate

    0.17 mmol L−1, FE: 62%

    [131]

    RuCE+RuCA modified Cu2ZnSn(S,Se)4

    CO2-saturated water, -0.6 V vs. Ag/AgCl, 400<λ<800 nm, 3 h

    Formate

    0.49 mmol L−1, FE: 80%

    [34]

    Ru(II)-Re(I) supramolecular modified p-type NiO

    Et4NBF4 (0.1 mol L−1) in DMF/TEOA (5:1, v/v) solution, −1.2 V vs. Ag/AgNO3, >460 nm, 3h

    CO

    255 nmol, TONco: 32 FE: 62% (0–3 h),98% (3–5 h)

    [134]

    Fe porphyrin complex modified B-doped p-Si

    [NBu4][BF4] (0.1 mol L−1) in MeCN/5% DMF (v/v) solution, −1.1 V vs. SCE, <650 nm (90 mW cm–2), 6 h

    CO

    ca. 140 μmol, TON: 175 FE: 80%

    [139]

    Molecular Mn catalyst immobilized mesoporous TiO2

    Bu4NBF4 (0.1 mol L−1) in CH3CN/H2O (19:1, v/v) solution, −1.7 V vs. Fc/Fc+, AM 1.5G (100 mW cm–2), 2h

    CO

    3.75±0.56 μmol, TON: 112±17 FE: 67±5%

    [140]

    Pyridine+p-CuInS2 films

    Na2SO4 (0.1 mol L−1, pH 5.2), overpotential of 20 mV, AM 1.5G light (100 mW cm–2), 11 h

    CH3OH

    1.2 mmol L−1, FE: 97%

    [35]

    Pyridine+p-CdTe/FTO

    NaHCO3 (0.1 mol L−1) with citric acid buffer (0.1 mol L−1, pH 5), −0.6 V vs. SCE, visible light, 6 h

    HCOOH

    4.19 mA cm−2,0.167 mmol, FE: 60.7%

    [146]

    Polypyrrole coated p-CdTe

    KHCO3 (0.1 mol L−1, pH 6.7), −0.2 V vs. RHE, >420 nm,6 h

    HCOOH, CO

    111.1 nmol h−1 cm−2, FE: 37.2%41.1 nmol h−1 cm−2, FE: 13.8%

    [158]

    PMAEMA/CdTe QDs film

    NaClO4 (0.1 mol L−1), −0.45 V vs. Ag/AgCl, 500 W Xe-Hg lamp, 3 h

    HCHO

    ca. 5% (μmol HCHO/μmol CO2)

    [159]

    CODH functionalized Dye-sensitized p-NiO

    MES (0.2 mol L−1, pH 6), −0.27 V vs. SHE, visible light

    CO

    ca. 25 μA cm−2

    [32]

    Rh-(FDH-FaldDH-ADH) enzymes modified BiFeO3 photocathode

    Na3PO4 buffer (0.1 mol L−1, pH 7), electrical bias: 0.8 V, >420 nm(150 mW cm−2),6 h

    CH3OH

    220 μmol L−1 h−1, 1280 μmol gcat−1 h−1

    [165]

  • Table 4   Selected recently reported PEC setups for CO reduction

    Electrode

    Condition

    Main products

    Efficiency

    Ref.

    Combining photoanodes with dark cathodes

     

    Photoanode: Pt modified TNTsCathode: Pt modified rGO on Ni foam

    Anolyte: NaCl (1 mol L−1), catholyte: NaHCO3(1 mol L−1), constant potential: 2 V, Xe lamp (10 mW cm−2), 8 h

    CH3OH, C2H5OH, HCOOH, CH3OOH

    1.13 μmol h−1 cm−2

    [169]

    Photoanode: Pt modified TNTsCathode: Pt modified rGO on Ni foam

    Anolyte: NaCl (1 mol L−1), catholyte: NaHCO3(1 mol L–1), constant potential: 2 V, Xe lamp (10 mW cm–2), 24 h

    CH3OH, C2H5OH, HCOOH, CH3OOH

    1.5 μmol h−1 cm−2

    [170]

    Photoanode: Pt modified TNTsCathode: Pt modified rGO on Cu foam

    Anolyte: H2SO4 (0.5 mol L−1), catholyte: NaHCO3(0.5 mol L−1), constant potential: 2 V, Xe lamp

    CH3OH, C2H5OH, HCOOH, CH3OOH

    4.34 μmol h−1 cm−2

    [171]

    Photoanode: TiO2 nanorodsCathode: Cu2O on Cu substrate

    KHCO3 (0.1 mol L−1), 0.75 V vs. RHE, AM 1.5Glight (100 mW cm−2), 3 h

    CH4, CO, CH3OH

    FE: 54.63%FE: 30.03%FE: 2.79%

    [31]

    Photoanode: WO3 filmCathode: glassy carbon type Cu

    CO2-purged KHCO3 (0.5 mol L−1, pH 7.5),0.75 V vs. RHE, >420 nm(100 mW cm–2),1 h

    CH4

    FE: 67%

    [44]

    Photoanode: WO3 filmCathode: Sn/SnOx

    CO2-purged KCl (0.5 mol L−1, pH 5.2), 0.8 V vs.RHE, >420 nm(100 mW cm−2),3 h

    HCOOH, CO

    FE: 26.8%FE: 17.5%

    [44]

    Photoanode: Ni coated n-type SiCathode: nanoporous Ag film

    CO2-saturated Na2SO4 (0.5 mol L−1),external bias: 2V >400 nm,3 h

    CO

    10 mA cm−2,FE: 70%

    [43]

    Combining photoanodes with photocathodes

     

    Photoanode: p-Si nanowiresPhotocathode: n-TiO2 nanotube arrays

    CO2-saturated NaHCO3 (1 mol L−1), −1.5 V vs.Ag/AgCl, AM 1.5G light, 30 min

    CO, CH4, C2–C4products

    824 nmol L−1 h−1 cm−2201.5 nmol L−1 h−1 cm−2

    [30]

    Photoanode: Pt loaded TiO2Photocathode: p-type InP/Ru complex

    NaHCO3 (0.01 mol L−1), no external appliedelectrical bias, AM 1.5G light, 24 h

    Formate

    TON: >17,FE: >70%SFE: 0.03–0.04%

    [45]

    Photoanode: CoOx/TaONPhotocathode: Ru(II)-Re(I)complex-p-NiO

    CO2-saturated NaHCO3 (0.05 mol L−1, pH 6.6), external electrical bias: 0.3 V, >400 nm, 1 h

    CO

    79 nmol,TONco: 17,FE: 37%

    [46]

    Photovoltaic–based tandem electrocatalytic devices

     

    Photovoltaics: CH3NH3PbI3 perovskite solar cell Anode: oxidized Au film Cathode: IrO2

    CO2-saturated NaHCO3 (0.5 mol L−1, pH 7.2),

    supplied bias by photovoltaics: 2 V, AM 1.5Glight (100 mW cm−2), 18 h

    CO

    SCOE: 6.5%FE: 80–90%

    [47]

    Photovoltaics: GaInP/GaInAs/Ge solar cell Anode: SnO2 modified CuO nanowires Cathode: SnO2 modified CuO nanowires

    Anolyte: CsOH (0.25 mol L−1),Catholyte: CsHCO3 (0.1 mol L−1)

    ,

    supplied bias by photovoltaics: 2.24 V,AM 1.5G light (100 mW cm−2), 5 h

    CO

    SCOE: 13.4%FE: 81% on average

    [48]

    Photovoltaics: Si based solar cells Photoanode: Co-Pi/W:BiVO4Photocathode: Pd/NRx@TiO2

    CO2-saturated KHCO3 (0.1 mol L−1),

    supplied bias by photovoltaics: 0.6 V by 5 W LED light, Xe lamp (200 mW cm−2) for photoelectrode

    CH3OH

    106 μmol L−1 h−1 cm−2AQY: 95%

    [187]

    Wireless monolithic devices

     

    p-InP/[RuCP] + r-STO

    H3PO4 buffered NaHCO3 (0.1 mol L−1 pH 7.7), AM 1.5G light, no external applied electrical bias, 3 h

    Formate

    0.94 μmol,SFE: 0.08%

    [132]

    IrOx/SiGe-jn/CC/p-RuCP

    H3PO4 buffered NaHCO3 (0.1 mol L−1 pH 7.7), AM 1.5G light, no external applied electrical bias, 2 h

    Formate

    50.2 μmol,SFE: 4.6%

    [190]