Here, we evaluate three different noble metal co-catalysts (Pd, Pt, and Au) that are present as single atoms (SAs) on the classic benchmark photocatalyst, TiO2. To trap the single atoms on the surface, we introduced controlled surface vacancies (Ti3+-Ov) on anatase TiO2 nanosheets by a thermal reduction treatment. After anchoring identical loadings of single atoms of Pd, Pt, and Au, we measure the photocatalytic H2 generation rate and compare it to the classic nanoparticle co-catalysts on the nanosheets. While nanoparticles yield the well-established the hydrogen evolution reaction activity sequence (Pt > Pd > Au), for the single atom form, Pd radically outperforms Pt and Au. Based on density functional theory (DFT), we ascribe this unusual photocatalytic co-catalyst sequence to the nature of the charge localization on the noble metal SAs embedded in the TiO2 surface.

Department of Chemistry Faculty of Science King Abdulaziz University P O Box 80203 Jeddah 21569 Saudi Arabia

Department of Materials Science and Engineering School of Industrial Engineering and Management KTH Royal Institute of Technology Brinellvägen 23 100 44 Stockholm Sweden

Department of Physics and Astronomy Uppsala University Box 516 751 20 Uppsala Sweden

Faculty of Physical Chemistry University of Belgrade Studentski trg 12 16 Belgrade 11000 Serbia

Institute for Surface Science and Corrosion WW4 LKO Department of Materials Science University of Erlangen Nuremberg Martensstraße 7 91058 Erlangen Germany

Institute of Micro and Nanostructure Research and Center for Nanoanalysis and Electron Microscopy University of Erlangen Nuremberg IZNF Cauerstraße 3 91058 Erlangen Germany

Regional Centre of Advanced Technologies and Materials Šlechtitelů 27 Olomouc 78371 Czech Republic

See more in PubMed

Daelman N., Capdevila-Cortada M., López N. Dynamic charge and oxidation state of Pt/CeO2 single-atom catalysts. Nat. Mater. 2019;18:1215–1221. doi: 10.1038/s41563-019-0444-y. PubMed DOI

Flytzani-Stephanopoulos M. Gold atoms stabilized on various supports catalyze the water-gas shift reaction. Acc. Chem. Res. 2014;47:783–792. doi: 10.1021/ar4001845. PubMed DOI

Fu Q., Saltsburg H., Flytzani-Stephanopoulos M. Active nonmetallic Au and Pt species on ceria-based water-gas shift catalysts. Science. 2003;301:935–938. doi: 10.1126/science.1085721. PubMed DOI

Gao C., Low J., Long R., Kong T., Zhu J., Xiong Y. Heterogeneous single-atom photocatalysts: fundamentals and applications. Chem. Rev. 2020;120:12175–12216. doi: 10.1021/acs.chemrev.9b00840. PubMed DOI

Gates B.C., Flytzani-Stephanopoulos M., DIxon D.A., Katz A. Atomically dispersed supported metal catalysts: perspectives and suggestions for future research. Catal. Sci. Technol. 2017;7:4259–4275. doi: 10.1039/c7cy00881c. DOI

Giannozzi P., Andreussi O., Brumme T., Bunau O., Buongiorno Nardelli M., Calandra M., Car R., Cavazzoni C., Ceresoli D., Cococcioni M. Advanced capabilities for materials modelling with Quantum ESPRESSO. J. Phys. Condens. Matter. 2017;29:465901. doi: 10.1088/1361-648X/aa8f79. PubMed DOI

Giannozzi P., Baroni S., Bonini N., Calandra M., Car R., Cavazzoni C., Ceresoli D., Chiarotti G.L., Cococcioni M., Dabo I. Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials. J. Phys. Condens. Matter. 2009;21:395502. doi: 10.1088/0953-8984/21/39/395502. PubMed DOI

Giordano L., Pacchioni G., Bredow T., Sanz J.F. Cu, Ag, and Au atoms adsorbed on TiO2(110): cluster and periodic calculations. Surf. Sci. 2001;471:21–31. doi: 10.1016/S0039-6028(00)00879-7. DOI

Heiz U., Sanchez A., Abbet S., Schneider W.-D. Catalytic oxidation of carbon monoxide on monodispersed platinum clusters: each atom counts. J. Am. Chem. Soc. 1999;121:3214–3217. doi: 10.1021/ja983616l. DOI

Hejazi S., Mohajernia S., Osuagwu B., Zoppellaro G., Andryskova P., Tomanec O., Kment S., Zbořil R., Schmuki P. On the controlled loading of single platinum atoms as a Co-catalyst on TiO2 anatase for optimized photocatalytic H2 generation. Adv. Mater. 2020;32 doi: 10.1002/adma.201908505. 1908505 (1–9) PubMed DOI

Hu Y., Qu Y., Zhou Y., Wang Z., Wang H., Yang B., Yu Z., Wu Y. Single Pt atom-anchored C3N4: a bridging Pt–N bond boosted electron transfer for highly efficient photocatalytic H2 generation. Chem. Eng. J. 2021;412:128749. doi: 10.1016/j.cej.2021.128749. DOI

Kudo A., Miseki Y. Heterogeneous photocatalyst materials for water splitting. Chem. Soc. Rev. 2009;38:253–278. doi: 10.1039/B800489G. PubMed DOI

Lačnjevac U., Vasilić R., Dobrota A., Đurđić S., Tomanec O., Zbořil R., Mohajernia S., Nguyen N.T., Skorodumova N., Manojlović D. High-performance hydrogen evolution electrocatalysis using proton-intercalated TiO2 nanotube arrays as interactive supports for Ir nanoparticles. J. Mater. Chem. A. 2020;8:22773–22790. doi: 10.1039/D0TA07492F. DOI

Liu J. Catalysis by supported single metal atoms. ACS Catal. 2017;7:34–59. doi: 10.1021/acscatal.6b01534. DOI

Mohajernia S., Andryskova P., Zoppellaro G., Hejazi S., Kment S., Zboril R., Schmidt J., Schmuki P. Influence of Ti3+ defect-type on heterogeneous photocatalytic H2 evolution activity of TiO2. J. Mater. Chem. A. 2020;8:1432–1442. doi: 10.1039/C9TA10855F. DOI

Monkhorst H.J., Pack J.D. Special points for Brillouin-zone integrations. Phys. Rev. B. 1976;13:5188–5192. doi: 10.1103/PhysRevB.13.5188. DOI

Naldoni A., Altomare M., Zoppellaro G., Liu N., Kment Š., Zbořil R., Schmuki P. Photocatalysis with reduced TiO2 : from black TiO2 to cocatalyst-free hydrogen production. ACS Catal. 2019;9:345–364. doi: 10.1021/acscatal.8b04068. PubMed DOI PMC

Nørskov J.K., Bligaard T., Logadottir A., Kitchin J.R., Chen J.G., Pandelov S., Stimming U. Trends in the exchange current for hydrogen evolution. J. Electrochem. Soc. 2005;152:J23. doi: 10.1149/1.1856988. DOI

Osterloh F.E. Inorganic nanostructures for photoelectrochemical and photocatalytic water splitting. Chem. Soc. Rev. 2013;42:2294–2320. doi: 10.1039/C2CS35266D. PubMed DOI

Parsons R. The rate of electrolytic hydrogen evolution and the heat of adsorption of hydrogen. Trans. Faraday Soc. 1958;54:1053. doi: 10.1039/tf9585401053. DOI

Perdew J.P., Burke K., Ernzerhof M. Generalized gradient approximation made simple. Phys. Rev. Lett. 1996;77:3865–3868. doi: 10.1103/PhysRevLett.77.3865. PubMed DOI

Qiao B., Wang A., Yang X., Allard L.F., Jiang Z., Cui Y., Liu J., Li J., Zhang T. Single-atom catalysis of CO oxidation using Pt1/FeOx. Nat. Chem. 2011;3:634–641. doi: 10.1038/nchem.1095. PubMed DOI

Seh Z.W., Kibsgaard J., Dickens C.F., Chorkendorff I., Nørskov J.K., Jaramillo T.F. Combining theory and experiment in electrocatalysis: insights into materials design. Science. 2017;355:eaad4998. doi: 10.1126/science.aad4998. PubMed DOI

Serpone N., Salinaro A., Emeline A., Ryabchuk V. Turnovers and photocatalysis: a mathematical description. J. Photochem. Photobiol. A. Chem. 2000;130:83–94. doi: 10.1016/S1010-6030(99)00217-8. DOI

Sheng W., Myint M., Chen J.G., Yan Y. Correlating the hydrogen evolution reaction activity in alkaline electrolytes with the hydrogen binding energy on monometallic surfaces. Energy Environ. Sci. 2013;6:1509. doi: 10.1039/c3ee00045a. DOI

Trasatti S. Work function, electronegativity, and electrochemical behaviour of metals. J. Electroanal. Chem. Interfacial Electrochem. 1972;39:163–184. doi: 10.1016/S0022-0728(72)80485-6. DOI

Wang A., Li J., Zhang T. Heterogeneous single-atom catalysis. Nat. Rev. Chem. 2018;2:65–81. doi: 10.1038/s41570-018-0010-1. DOI

Wang Q., Domen K. Particulate photocatalysts for light-driven water splitting: mechanisms, challenges, and design strategies. Chem. Rev. 2020;120:919–985. doi: 10.1021/acs.chemrev.9b00201. PubMed DOI

Wang Z., Yang J., Gan J., Chen W., Zhou F., Zhou X., Yu Z., Zhu J., Duan X., Wu Y. Electrochemical conversion of bulk platinum into platinum single-atom sites for the hydrogen evolution reaction. J. Mater. Chem. A. 2020;8:10755–10760. doi: 10.1039/D0TA02351E. DOI

Wenderich K., Mul G. Methods, mechanism, and applications of photodeposition in photocatalysis: a review. Chem. Rev. 2016;116:14587–14619. doi: 10.1021/acs.chemrev.6b00327. PubMed DOI

Yang X.-F., Wang A., Qiao B., Li J., Liu J., Zhang T. Single-atom catalysts: a new frontier in heterogeneous catalysis. Acc. Chem. Res. 2013;46:1740–1748. doi: 10.1021/ar300361m. PubMed DOI

Yao Y., Gu X.-K., He D., Li Z., Liu W., Xu Q., Yao T., Lin Y., Wang H.-J., Zhao C. Engineering the electronic structure of submonolayer Pt on intermetallic Pd 3 Pb via charge transfer boosts the hydrogen evolution reaction. J. Am. Chem. Soc. 2019;141:19964–19968. doi: 10.1021/jacs.9b09391. PubMed DOI

Zhou Z., Wang S., Zhou W., Wang G., Jiang L., Li W., Song S., Liu J., Sun G., Xin Q. Novel synthesis of highly active Pt/C cathode electrocatalyst for direct methanol fuel cell. Chem. Commun. 2003;7:394–395. doi: 10.1039/b211075j. PubMed DOI

Zhu C., Fu S., Shi Q., Du D., Lin Y. Single-atom electrocatalysts. Angew. Chem. - Int. Ed. 2017;56:13944–13960. doi: 10.1002/anie.201703864. PubMed DOI

Zubieta C.E., Aquino-Linarez L.G., Fuente S.A., Belelli P.G., Ferullo R.M. Growth and structure of Cu, Ag and Au clusters on α-Fe2O3(0001): a comparative density functional study. Comput. Mater. Sci. 2020;173:109392. doi: 10.1016/j.commatsci.2019.109392. DOI

Single Atom Cocatalysts in Photocatalysis

Facet-Control versus Co-Catalyst-Control in Photocatalytic H2 Evolution from Anatase TiO2 Nanocrystals