We carry out fundamental studies on industrially relevant electrochemical reactions. Electrochemistry has evolved to be increasingly relevant in providing answers to energy and material sustainability. In the march towards gigawatt-level deployment of technologies such as electrolysers and fuel cells questions of energy efficiency and stability form a central theme.  Removing activity and stability bottlenecks requires deep understanding of the multifactorial interactions involved in both material discovery and device innovation. A fruitful operation of the device is often an act of delicate balance between several factors such as electrochemical potential, nature of the electrolyte and nature of reactants and products.

We rely on in  situ / operando (in operation) level studies to develop insights on material transformation quickly. This approach helps us to arrive at conclusions such as optimum reaction conditions and methodologies to mitigate degradation quickly. Theoretical atomistic level modeling helps to compare relative experimental scenarios and develop a more robust understanding of mechanisms of action.

We look at a range of industrially fundamental electrochemical reactions. Water oxidation forms the weakest link between converting renewable energy to products such as hydrogen or hydrocarbons. The sheer abundance of water molecules on earth makes if the only molecule that can be profitably oxidised at scale against any cathodic reaction such as hydrogen evolution. 

Oxygen being the most abundant oxidant forms the most important molecule that can be reduced against any anode. Reactions such as oxidation of molecules such as hydrogen or methanol require oxygen counter electrodes. The reaction is of fundamental importance in context of fuel cells and industrial reactions such as chloralkali process.

Platinum forms an important electrode in electrochemical oxidation/reduction reactions  due it its fundamental energetics of Pt-O and Pt-H bond formation. Inspite of its rarity it's likely to stay due to the sheer value it provides. Reactions on Pt and modified Pt electrodes such as hydrogen evolution, alcohol oxidation, formic acid oxidation remain relevant at this day and age.

CO2 electro-reduction to fuels is one of the most vital reactions in the generation of energy carriers from CO2. These carriers can turn the hydrocarbon "fuel burning cycle" CO2 - neutral. Solid Oxide electrodes running at temperatures in excess of 700 degrees celsius can often make reaction kinetics much easier.  We focus on developing new SOEC cathodes and membrane electrode assemblies that can carry out these reactions efficiently. 

Co-doped Copper oxide electrodes for selective 4e reduction of oxygen

Binding energy at the active site is a critical parameter that influences the activity and selectivity of oxide electrodes. Pristine oxide electrodes have in general, been projected to have limited activity as the M-O bond strength on the surface of a pristine oxide is not sufficiently  strong to help in the subsequent O-O bond cleavage step required in ORR.  This affects both activity and selectivity. Shekhar Biswal in our lab has tried to circumvent this using a new strategy where he doped Co into a CuOx matrix. CuOx has (Cu2+) square planar coordination of oxygen atoms around Cu whereas Co oxide prefers to be in an octahedral coordination irrespective of its oxidation state. This strategy of doping Co ions into CuOx matrix creates sites of high unsaturation/stress at Co sites which is compensated by binding strongly with the in coming oxygen. We have shown that this strategy results in immense increase in O-O bond cleavage activity and results in a highly selective material that can cleave O-O bonds. The activity against O2 also translates to activity against H2O2. The catalyst has excellent selectivity over a large potential range relevant for fuel cells.

Reason of enhancement of formic acid oxidation on Pt with a monolayer of Pb

Formic acid (HCOOH) remains an important energy carrier molecule. It's essentially a molecule that is already loaded with CO2 and technically does not need oxygen to undergo oxidation chemistry at the anode. It is also one of the easiest molecules to obtain upon reduction of CO2. It has been well known since the 1990s..that addition of an underpotentially deposited layer of Pb results in significant enhancement of oxidation currents of formic acid. We for the first time, using extensive theoretical modeling and experiments, have shown that it's is the inhibition of H adsorption on Pt sites by adsorbed Pb sites nearby that results in significant enhancement of formic acid oxidation. Without the presence of inhibiting hydrogen, both Pt and Pt{Pb} surfaces can react with HCOOH to form CO2. Experimentally, electrodes were evaluated in Pb-containing solutions for measurement of Hupd adsorption free energies and kinetics within solutions with and without Pb.

Reaction free energy calculations on Pt and Pt{Pb}surface

Reaction-free energies were computed on low-index Pt surfaces. The lowest energy species predict the nature of the surface species on the Pt surface in aqueous medium. The underpotentially deposited H (Hupd) coverage and presence of O or OH species on the Pt surface were correctly predicted as per experimental results on single crystal surfaces from Feliu et. al. Upon adsorption of Pb it was  shown that Hupd is significantly suppressed.

Electronic Structure of H adsorption Pt and Pb surfaces {A chemical bonding perspective}

Pt adsorption results in significant altering of the surface electronic structure of Pt which affects all the adsorption energies on nearby Pt. It results in surface Pt having a net negative charge as opposed to a positive charge on the pristine surface. A chemical bonding analysis of the Pt and adsorbed H using energy weighted orbital overlap analysis (COHP) was carried out in presence and absence of Pb surface ad-atom.