Synergistic influence of multivalent Ruδ+ on a CeOx nanocatalyst for self-powered efficient electrochemical water splitting

Abstract

In spite of the rapid development of portable water-splitting devices based on rechargeable metal–air batteries, there is a scarcity of efficient multifunctional electrocatalysts (ECs) for oxygen reduction, oxygen evolution, and hydrogen evolution reactions (ORR/OER/HER). Herein, a multicomponent–multivalent coupling strategy involving surface-interface engineering is adopted for the development of an efficient trifunctional (TF) EC through the integration of dominant CeO_x (CO) with a small fraction of Ru⁰ (R⁰) and RuO_x (RO). Under tuned metal valency-composition, the designed multi-interfacial CO/R⁰/RO nanocomposite (NComp) shows enhanced ORR (E_1/2 of 0.936 V), OER [overpotential (η₁₀) of 166 mV at 10 mA cm⁻²], and HER (η₁₀ of 58 mV) activity. Moreover, the drastically enhanced activity of CO/R⁰/RO is achieved with a small cell voltage of as low as 1.49 V, required to accomplish overall water splitting (OWS) at 10 mA cm⁻². In addition, a large peak power density of 376.4 mW cm⁻² and a low charge–discharge voltage gap of 0.247 V are observed for zinc–air batteries (ZABs) with admirable cycling stability (over 2000 h/12 000 cycles). In addition to ZABs, CO/R⁰/RO NComp is employed to mimic the functionality of Li–air batteries (LABs). For practical utility, an integrated device consisting of a symmetric two-electrode water splitting electrolyzer powered by two series-connected ZABs is realized using CO/R/RO as a single catalyst, which efficiently drives OWS and effectively produces H₂ and O₂ with production rates of 399.3 and 199.6 μL min⁻¹, respectively. Moreover, the observed high faradaic efficiencies of 98.9% for the HER and 98.4% for the OER illustrate the effective energy conversion and high efficiency of this self-powered system. Thus, this work presents a feasible strategy of surface engineering via alteration of surface electronic states and concurrent fabrication of value-added highly efficient TF ECs, paving the way for their widespread adoption in energy-related devices.