[scientizscht (OP)]

What is the most efficient CO2 catalyst?

What are the bottlenecks of capturing and converting CO2?

[alancalverd]

Presumably you want to turn CO2 into something more useful than wood or food, since the most efficient hydrolysis of atmospheric CO2 to carbohydrates and hydrocarbons is to do nothing, stop farming animals, and let the forests re-grow.

Audi have a process for synthesising motor fuel from atmospheric CO2 and there are a number of published papers on the synthesis of alkanes with Fe, Mo or Cr catalysts.

https://www.pnas.org/content/116/20/9693 is particularly interesting aas it takes a "whole system" approach to energetics.

[Bored chemist]

What is the most efficient CO2 catalyst?

What are the bottlenecks of capturing and converting CO2?

The first part  doesn't make sense  unless you say what reaction of CO2 you want to catalyse.
The answer to the second is "providing enough cheap energy" (or finding space for trees etc).

[evan_au]

What is the most efficient CO2 catalyst?

The first part  doesn't make sense  unless you say what reaction of CO2 you want to catalyse.

If the reaction you wish to catalyse is: CH₄ + 3O₂ → CO₂ + 2H₂O

Then a very small spark is all you need to get it started, and then the reaction will carry on merrily all by itself, producing all the CO₂ you could ever wish for. No real catalyst is needed.

The reverse reaction requires a considerable input of energy, and so a catalyst by itself is not enough.