Effect of Cooperative Redox Property and Oxygen Vacancies on Bifunctional OER and HER Activities of Solvothermally Synthesized CeO₂/CuO Composites

Abstract

Herein, we report the synthesis of the CeO 2 /CuO composite as a bifunctional oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) electrocatalyst in a basic medium. The electrocatalyst with an optimum 1:1 CeO 2 /CuO shows low OER and HER overpotentials of 410 and 245 mV, respectively. The Tafel slopes of 60.2 and 108.4 mV/dec are measured for OER and HER, respectively. More importantly, the 1:1 CeO 2 /CuO composite electrocatalyst requires only a 1.61 V cell voltage to split water to achieve 10 mA/cm 2 in a two-electrode cell. The role of oxygen vacancies and the cooperative redox activity at the interface of the CeO 2 and CuO phases is explained in the light of Raman and XPS studies, which play the determining factor for the enhanced bifunctional activity of the 1:1 CeO 2 /CuO composite. This work provides guidance for the optimization and design of a low-cost alternative electrocatalyst to replace the expensive noble-metalbased electrocatalyst for overall water splitting.

RuSe2–CoTe Heterogeneous Surfaces Coated with NC Layer for Excellent HER Performance under Alkaline Condition

“…The construction of heterogeneous surfaces can effectively modulate Ru atoms electronically and promote HER reaction. The Tafel slope of RuSe 2 –CoTe/NC is 67.8 mV dec –1 , indicating that the rate-determining is the Heyrovsky step. , It is worth noting that the HER reaction follows the Heyrovsky–Volmer mechanism under alkaline conditions normalVolmer step : normalH 2 normalO + normale − → OH − + normalH ad normalHeyrovsky step : normalH 2 normalO + normale − + normalH ad → OH − + normalH 2 …”

“…The Tafel slope of RuSe 2 −CoTe/NC is 67.8 mV dec −1 , indicating that the rate-determining is the Heyrovsky step. 48,49 It is worth noting that the HER reaction follows the Heyrovsky−Volmer mechanism under alkaline conditions 50 (2)…”

Ferroelectric Polarization and Iron Substitution Synergistically Boost Electrocatalytic Oxygen Evolution Reaction in Bismuth Oxychloride Nanosheets

“…Electrocatalytic water splitting is gaining huge attention for generating pure hydrogen (and oxygen) as a fuel. , In the electrocatalytic water splitting process, the electrocatalyst lowers the overpotential through the direct transfer of electrons and provides a less energetic pathway for chemical reactions occurring on the electrode surface. However, the efficiency of this process is limited by the stagnant kinetics of the anodic and cathodic reactions for oxygen evolution and hydrogen evolution reactions. , OER thermodynamically can occur in acidic, neutral, and alkaline conditions which involves the transfer of four electrons at a higher potential than that of the theoretical water splitting potential (1.23 V). − The oxygen evolution reactions in acidic and basic media follow these processes: 2 H 2 normalO → O 2 + 4 H + + 4 e − ( acidic ) 4 OH − → O 2 + 2 H 2 O + 4 e − false( alkaline false) …”

“…Electrocatalytic water splitting is gaining huge attention for generating pure hydrogen (and oxygen) as a fuel. 15,16 In the electrocatalytic water splitting process, the electrocatalyst lowers the overpotential through the direct transfer of electrons and provides a less energetic pathway for chemical reactions occurring on the electrode surface. However, the efficiency of this process is limited by the stagnant kinetics of the anodic and cathodic reactions for oxygen evolution and hydrogen evolution reactions.…”

4f–2p–3d orbital overlap in a metal–organic framework-derived CeO2/CeCo-LDH heterostructure promotes water oxidation

“…Previously, the improvement of the oxygen redox activities of the Co/CeO 2 and OER and HER activities of CuO/CeO 2 catalysts have been reported because of the heterojunction formation. 22,23 As the amount of Ce III in Co-LDH increased, the overpotential for the OER decreased, reached an optimum value for CeCo-2, and increased after that (Fig. S8, left, ESI †).…”