Improving the Sulfurophobicity of the NiS-Doping CoS Electrocatalyst Boosts the Low-Energy-Consumption Sulfide Oxidation Reaction Process

Abstract

Producing sulfur from a sulfide oxidation reaction (SOR)-based technique using sulfide aqueous solution has attracted considerable attention due to its ecofriendliness. This study demonstrates that NiS-doped cobalt sulfide NiS-CoS-supported NiCo alloy foam can deliver the SOR with superior electrocatalytic activity and robust stability compared to reported non-noble metal-based catalysts. Only 0.34 V vs RHE is required to drive a current density of 100 mA cm–2 for the SOR. According to the experiment, the catalyst exhibits a unique sulfurophobicity feature because of the weak interaction between sulfur and the transition metal sulfide (low affinity for elemental sulfur), preventing electrode corrosion during the SOR process. More impressively, the chain-growth mechanism of the SOR from short- to long-chain polysulfides was revealed by combining electrochemical and spectroscopic in situ methods, such as in situ ultraviolet–visible and Raman. It is also demonstrated that electrons can transfer straight from the sulfion (S2–) to the active site on the anode surface during the low-energy-consumption SOR process. This work provides new insight into simultaneous energy-saving hydrogen production and high-value-added S recovery from sulfide-containing wastewater.

Sulfur Recovery Assisted Electrochemical Water Splitting for H2 Production Using CoMo-Based Nanorod Arrays Catalysts

“…It is possible to determine the stepwise oxidation pathway of CoMoO 4 /NF in the SOR process by combining this with the earlier findings. Prior to being oxidized to the S 8 , the adsorbed S 2– ions undergo gradual oxidation to form intermediates of short-chain polysulfides, such as S 2 2– , S 3 2– , S 4 2– , and S 8 . − Therefore, the SOR reaction pathways can be inferred as n S 2– – 2­( n – 1)­e – + n OH – → S n 2– + n H 2 O. The above conclusion is consistent with the reported theoretical calculation results …”

“…In order to avoid catalyst poisoning and reduce SOR overpotential, current research on sulfur oxidation catalysts focuses mostly on the development of transition metal catalysts (such as Co 3 S 4 , CoNi@NGs, NiCu–MoS 2 , and so on). The affinity of transition metal to sulfur is low, which avoids the passivation of the catalyst. − Yang et al prepared Co 3 S 4 nanowires on a nickel foam substrate and proved that it can efficiently accelerate the conversion of polysulfide intermediates. The deposition of S 8 on the electrode is reduced during the S 8 desorption stage, which improves mass transfer efficiency .…”