Mesoporous PdAg Nanospheres for Stable Electrochemical CO₂ Reduction to Formate

Abstract

Palladium is a promising material for electrochemical CO 2 reduction to formate with high Faradaic efficiency near the equilibrium potential. It unfortunately suffers from problematic operation stability due to the CO poisoning on surface. Here, we demonstrate that alloying is an effective strategy to alleviate this problem. Mesoporous PdAg nanospheres with uniform size and composition are prepared from the co-reduction of palladium and silver precursors in aqueous solution using dioctadecyldimethylammonium chloride as the structure directing agent. The best candidate can initiate CO 2 reduction at zero overpotential, and achieve high formate selectivity close to 100% and great stability even at <-0.2 V versus reversible hydrogen electrode. The high selectivity and stability are believed to result from the electronic coupling between Pd and Ag, which lowers the d-band center of Pd and thereby significantly enhances its CO tolerance, as evidenced by both electrochemical analysis and theoretical simulations.

Alloyed Palladium–Silver Nanowires Enabling Ultrastable Carbon Dioxide Reduction to Formate

“…Although such a strategy has been applied as a general design principle of Pd alloys for electrocatalytic oxygen reduction reaction and alcohol oxidation reaction, [34][35][36][37] the alloying effect is much less explored and appreciated for CO 2 RR until very recently. [38][39][40][41] In this contribution, we investigate the great potential of 1D alloy nanowires of Pd and Ag in CO 2 RR electrocatalysis. Ag is selected as the second metal in the alloy for its electron-rich state and weak CO binding strength.…”

Promoting Electrocatalytic Hydrogen Evolution Reaction and Oxygen Evolution Reaction by Fields: Effects of Electric Field, Magnetic Field, Strain, and Light

“…In addition to water splitting, electrocatalytic reactions are also widely exploited in other realms. For example, CO 2 reduction reaction (CO 2 RR) can be exploited to produce carbon monoxide, [ 290 ] ethylene, [ 291 ] methane, [ 292 ] formate, [ 293–295 ] syngas, [ 296 ] or even gasoline fuel. [ 297 ] Ammonia, an essential chemical for both agriculture and industry applications, can be synthesized by nitrogen reduction reaction (NRR) under room temperature.…”

Towards the Large-Scale Electrochemical Reduction of Carbon Dioxide

“…Many studies have reported that the performance of the electrocatalytic CO2 reduction reaction (CO2RR) is compromised during electrolysis [2,[50][51][52]. This is often attributed to catalyst deactivation by the adsorption of reaction intermediates.…”

“…Thus, density-functional theory (DFT) calculations have often revealed higher binding energy between the poisoned catalysts and the implicated species. For instance, Pd metal is known to bind strongly to CO and is more likely to be poisoned and undergo activity degradation in a short duration of time due to the reduction of CO2 to CO [50][51][52]. The strong CO adsorption arises from an increase in 2π* back donation interaction (i.e., electron donation from the d orbitals of the metal substrate to the 2π* orbital of CO) as the formed bonding resonances are filled at a more negative potential [57].…”

“…This reduction in CO-binding energy also has been shown to be closely related to the specific type of alloying compound, with Pd3Co being both theoretically and experimentally the most resistant alloy against CO poisoning [55,74]. It has been commonly recognized that metal alloying can induce a lowering in the dband center, possibly via charge transfer, thus allowing more electrons to fill the metaladsorbate antibonding orbitals, leading to a reduction in CO back bonding and, hence, a significant reduction in CO poisoning [51]. This is supported by linear sweep voltammetry (LSV) data indicating that the alloying of Pd with Ag results in a lower CO stripping peak due to a weaker Pd-CO bond and, hence, a lower energy requirement for the removal of CO from the catalyst surface (Figure 13b) [51].…”