Tip-Intensified Interfacial Microenvironment Reconstruction Promotes an Electrocatalytic Chlorine Evolution Reaction

Abstract

Electrocatalysis applied in energy conversions has recently been associated with nanotips that catalyze extensive fuelforming or value-adding reactions. However, the enhanced catalytic behavior governed by tip-intensified microenvironment reconstruction is particularly elusive and is yet to be understood. Here, we demonstrated a homemade visualization platform to collect information from the local microenvironment of a solution near an electrode (LMSE) with high temporal−spatial resolution, thereby figuring out the sharp-tip enhancement effect for the chlorine evolution reaction (CER). Through visualization using sensitive Cl − and pH sensors, we confirmed that periodic nanoneedles were beneficial for field-induced anion concentration, giving priority to water dissociation and synchronously creating optimal pH conditions for triggering the CER, whereby the Cl − consumption rate within the LMSE was 1.3 times higher than that of the slab counterpart. Tip-enhanced effects meanwhile endowed the local microenvironment with intensified concentration and temperature gradients for continuous transport of Cl − substrates and effective diffusion of HClO products, whereby the oxygen evolution reaction for persistent CER activities was restrained. Our study provides definitive evidence that the optimal microenvironment functionalized with tip-intensified ion concentration from the electrolyte and water dissociation at tip sites are key to stabilize the crucial reaction intermediate for superior electrocatalytic performance.

Non-noble metal catalysts for preventing chlorine evolution reaction in electrolytic seawater splitting

“…In alkaline seawater, when the overpotential exceeds 490 mV, chloride ions are oxidized to hypochlorite, which becomes a powerful competitive reaction of the OER. 121,122…”

“…In alkaline seawater, when the overpotential exceeds 490 mV, chloride ions are oxidized to hypochlorite, which becomes a powerful competitive reaction of the OER. 121,122 We can analyze hypochlorite quantitatively by measuring the hypochlorite content in the electrolyte. It is commonly chosen to titrate hypochlorite aer the electrochemical stability test to represent the entire electrolytic process.…”

Critical challenges and opportunities for the commercialization of alkaline electrolysis: high current density, stability, and safety

“…Local concentration of reactants can be modulated by tip-enhanced local electric field and construction of a local coordination environment to enrich the local reactant concentration in the vicinity of the catalytic sites. [87][88][89][90] High-curvature structures can promote the aggregation of reactants around the surface of catalysts. It is attributed to the tip effect which refers to the aggregation of energy such as electrons, photons, and magnetism in the tip region with large curvature, resulting in the locally enhanced electric field at the sharp tip of a conductor.…”

Recent advances in energy-efficient chlorine production via HCl electrolysis

“…Although plenty of catalysts such as IrO 2 –TiO 2 NSA, 74 Ti/RuO 2 needles, 75 flower-like RuO 2 –TiO 2 , 76 Ti 0.35 V 0.35 Sn 0.25 Sb 0.05 -oxide, 77 Co 3 O 4 NBAs, 78 and hcp-cobalt rods 79 have been explored for chlorine evolution from NaCl, but there are limited works on electrode materials for HCl electrolysis. RuO 2 /TiO 2 is a state-of-art catalyst for chlorine evolution that has been utilized for chlorine electrolysis; there is still a reliance on noble metals.…”