Efficient photo-assisted electrocatalytic oxygen evolution using engineered CeO 2 Zahra Albu 1,4 , Nawal Al Abass 2 , Preetam Kumar Sharma 1 , Talal Qahtan 3 , Siming Huang 1 , Nusrat Rashid 1 , Galyam Sanfo 1 , Migual Pineda 5 , Abduljabar Al-Sayoud 6 , Bandar AlOtaibi* 4 , Mojtaba Abdi-Jalebi* 1 1 Institute for Materials Discovery, University College London, Malet Place, London WC1E 7JE, United Kingdom, 2 The Center of Excellence for Advanced Materials and Manufacturing, King Abdulaziz City for Science and Technology, Saudi Arabia, Riyadh 11442, 3 Hydrogen Technologies Institute, King Abdulaziz City for Science and Technology, Saudi Arabia, Riyadh 11442, 4 Department of Physics, College of Science and Humanity Studied in Alkharj, Riyadh 11442, Saudi Arabia, 5 Department of Chemical Engineering, University College London, London, WC1E 7JE, UK, 6 Department of Material Science and Engineering, King Fahd University of The production of green hydrogen through visible-light-driven water splitting represents an appealing avenue for sustainable and environmentally friendly hydrogen generation [1] . However, the efficiency of photoelectrocatalysis in solar-to-hydrogen conversion is constrained by the limited light absorption of most available semiconductor materials, which typically have wide bandgaps, restricting them to the UV range [2] . Consequently, there is a need to develop catalysts capable of absorbing visible light. In this context, we propose a strategy to enhance the photoelectrocatalytic activity of CeO 2 by doping it with transition metals such as Ni and Co. This doping extends the material's visible light absorption and introduces d-states within the forbidden bandgap. Verification of bandgap narrowing and extended visible light absorption was conducted through UV-vis diffuse reflectance, revealing that Ni and Co doping reduced the bandgap of CeO 2 from 3.0 eV to 2.7 eV and 2.6 eV, respectively. Density functional theory (DFT) calculations supported these findings, confirming bandgap narrowing and the presence of d-states. Moreover, photoelectrochemical measurements demonstrated superior photoelectrocatalytic activity in the Ni-doped sample compared to Co-doped CeO 2 . This enhanced catalytic performance is attributed to the introduction of d-states near the Fermi level through Ni doping, while Co doping introduced d-states located near the conduction band of CeO 2 . Our surface Slab calculations further revealed that Ni-doped CeO2 reduced the Gibbs energy for oxygen evolution reaction (OER) intermediate adsorption compared to pure and Co-doped CeO 2 . This suggests that doping plays a pivotal role in modulating the electronic environment of the catalyst, facilitating charge transfer through defect d-states near the Fermi level and accelerating reaction kinetics. In summary, our study underscores that doping CeO 2 with transition metals like Ni and Co can enhance its photoelectrocatalytic activity for green hydrogen production. Ni doping, in particular, leads to the creation of d-states near the Fermi level, resulting in improved catalytic performance. These findings contribute significantly to the development of efficient catalysts for visible-light-driven water splitting and pave the way for sustainable hydrogen production. References 1. Knezevic, M., Hoang, TH., Rashid, N., Abdi-Jalebi, M., Colbeau-Justin C., Ghazzal, M. N. Recent development in metal halide perovskites synthesis to improve their charge-carrier mobility and photocatalytic efficiency. Sci. China Mater. 66, 2545–2572 (2023). 2. FUJISHIMA, A., HONDA, K. Electrochemical Photolysis of Water at a Semiconductor Electrode. Nature 238, 37–38 (1972). Petroleum & Minerals, Saudi Arabia, Dammam, 31261 Email: bmalotaibi@kacst.edu.sa, m.jalebi@ucl.ac.uk
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