Abstract
The design and fabrication of highly cost-effective electrocatalysts with high activity, and stability to enhance the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has been considered to be one of the most promising approaches toward overall water splitting. In this study, sulfur-incorporated cobalt–iron (oxy)hydroxide (S-(Co,Fe)OOH) nanosheets were directly grown on commercial iron foam via galvanic corrosion and hydrothermal methods. The incorporation of sulfur into (Co,Fe)OOH results in superior catalytic performance and high stability in both the HER and OER conducted in 1 M KOH. The incorporation of sulfur enhanced the electrocatalytic activity by modifying the electronic structure and chemical states of (Co,Fe)OOH. An alkaline water electrolyzer for overall water splitting was fabricated using a two-electrode configuration utilizing the S-(Co,Fe)OOH bifunctional electrocatalyst in both the HER and OER. The fabricated electrolyzer outperformed a precious metal-based electrolyzer using Pt/C as the HER electrocatalyst and IrO2 as the OER electrocatalyst, which are the benchmark catalysts. This electrolyzer provides a lower potential of 1.641 V at 10 mA cm−2 and maintains 98.4% of its performance after 50 h of durability testing. In addition, the S-(Co,Fe)OOH-based electrolyzer successfully generated hydrogen under natural illumination upon its combination with a commercial silicon solar cell and exhibited a solar to hydrogen (STH) efficiency of up to 13.0%. This study shows that S-(Co,Fe)OOH is a promising candidate for application in the future renewable energy industry due to its high cost-effectiveness, activity, and stability during overall water splitting. In addition, the combination of a commercial silicon solar cell with an alkaline water electrolyzer has great potential for the production of hydrogen.
Highlights
Hydrogen energy has attracted a lot of attention as a nextgeneration renewable fuel with high density and in nite resources.[1]
The electrochemical surface area (ECSA) was calculated using eqn (1): ECSA 1⁄4 Cdl/Cs where Cs is the capacitance of an atomically smooth planar metal surface, which has a value of 40 mF cmÀ2.59 The cyclic voltammetry (CV) was analyzed versus the open circuit potential (OCP) a er all of the samples were held in the 1 M KOH electrolyte for 30 min
Sulfur was incorporated into the as-synthesized (Co,Fe)OOH during the hydrothermal procedure
Summary
Precious metal-based electrocatalysts are considered as benchmark electrocatalysts used for the HER (Ptbased) and OER (IrO2-based).[10,11] the high price, scarcity, and poor stability of these precious metals have restricted their use in large-scale applications.[6,12,13,14,15] To overcome these problems, many strategies have been developed using cost-effective and earth-abundant non-precious metals exhibiting high electrocatalytic activity.[16,17,18,19,20,21] For this purpose, several types of earth-abundant transition metal-based electrocatalysts, such as Fe, Co, Ni, Cu, and Mn, have been extensively investigated. Paper device manufacturing process.[44] In addition, considering that most rst-row transition metals are not stable under acidic conditions, it is essential to develop highly efficient bifunctional electrocatalysts that operate in an integrated alkaline environment for overall water splitting.[45,46] The high catalytic activity of transition metal-based hydroxides toward the OER has already been demonstrated in many studies. An alkaline water electrolyzer, fabricated using S-(Co,Fe)OOH as both the cathode and anode, provides better overall water splitting performance than a precious-metal-based water electrolyzer constructed using Pt/C and IrO2 as the cathode and anode
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