The Bismuth oxide (Bi₂O₃) gas diffusion electrode (GDE) is a 10 × 10 cm electrode used on the cathode side of a CO₂ electrolyzer. A GDE is a porous electrode that lets gaseous CO₂ reach the catalyst directly, avoiding the current limit caused by its low solubility in water (hundreds of mA cm⁻² are possible). Bismuth is known for formate selectivity; the Bi₂O₃ starting phase can convert, via a carbonate intermediate (Bi₂O₂CO₃), largely to metallic Bi in operation. In neutral/alkaline media the product is a formate salt; in solid-electrolyte cells, formic acid. Manufacturer reference selectivity is ≥90%.

The model code selects the option: CB standard, CT better stability, U enhanced gas transport, H enhanced flooding resistance; X marks versions suitable for solid-electrolyte cells (CBX, CTX, CBUX, CTUX). Flooding means electrolyte fills the pores and blocks CO₂, raising hydrogen formation. Catalyst loading is about 1 mg cm⁻² (manufacturer data); reference performance was measured in an MEA electrolyzer.

Key Features

Target product: formate (the anion of formic acid); reference selectivity ≥90% (manufacturer data)
Gas-diffusion structure: CO₂ reaches the catalyst from the gas phase, suited to high-current-density operation
10 × 10 cm size; catalyst loading ~1 mg cm⁻² (manufacturer data)
Standard (CB) and better-stability (CT) options
Enhanced gas transport (U) and enhanced flooding resistance (H) options; combined versions (CBUH, CTUH)
X versions are suitable for solid-electrolyte cells
Bismuth-based catalysts are known in the literature for high formate selectivity and good stability; results depend on operating conditions
Reference performance measured in an MEA electrolyzer; may vary with conditions

Technical Specifications

Product type	CO₂RR cathode gas diffusion electrode (GDE)
Catalyst	Bismuth oxide (Bi₂O₃)
Size	10 × 10 cm (100 cm²)
Target product	formate (the anion of formic acid)
Reference selectivity (manufacturer data)	≥90%
Catalyst loading	~1 mg cm⁻² (manufacturer data)
Options (model code)	CB standard; CT better stability; U enhanced gas transport; H enhanced flooding resistance (CBU, CTU, CBH, CTH, CBUH, CTUH); X solid-electrolyte compatible (CBX, CTX, CBUX, CTUX)
Reference test cell	Membrane electrode assembly (MEA) electrolyzer
Notes	Selectivity varies with test conditions (electrolyte, temperature, pressure, current density); catalyst/electrode preparation and testing services are not included

Available Options

Model	Description
Bi₂O₃-CB (Standard)	Standard
Bi₂O₃-CT (Better stability)	Better stability
Bi₂O₃-CBU (Enhanced gas transport)	Enhanced gas transport
Bi₂O₃-CTU (Better stability, enhanced gas transport)	Better stability, enhanced gas transport
Bi₂O₃-CBH (Enhanced flooding resistance)	Enhanced flooding resistance
Bi₂O₃-CTH (Better stability, enhanced flooding resistance)	Better stability, enhanced flooding resistance
Bi₂O₃-CBUH (Enhanced gas transport, enhanced flooding resistance)	Enhanced gas transport, enhanced flooding resistance
Bi₂O₃-CTUH (Better stability, enhanced gas transport, enhanced flooding resistance)	Better stability, enhanced gas transport, enhanced flooding resistance
Bi₂O₃-CBX (Suitable for solid-electrolyte cells)	Suitable for solid-electrolyte cells
Bi₂O₃-CTX (Suitable for solid-electrolyte cells, better stability)	Suitable for solid-electrolyte cells, better stability
Bi₂O₃-CBUX (Suitable for solid-electrolyte cells, enhanced gas transport)	Suitable for solid-electrolyte cells, enhanced gas transport
Bi₂O₃-CTUX (Suitable for solid-electrolyte cells, better stability, enhanced gas transport)	Suitable for solid-electrolyte cells, better stability, enhanced gas transport

For sizes and specifications not listed above, you can request a custom quotation through the Quote Form.

Applications

CO₂RR MEA (zero-gap) electrolyzer testing
GDE flow-cell studies
Comparing stability and flooding behavior across CB / CT / U / H options
Screening operating parameters such as anolyte/cation type, temperature, pressure and CO₂ flow
Salt-free formate/formic acid solution production in solid-electrolyte cells (X versions)