Nanoporous Palladium Hydride for Electrocatalytic N₂ Reduction under Ambient Conditions

Abstract

The electrocatalytic nitrogen reduction reaction (NRR) is an alternative eco‐friendly strategy for sustainable N2 fixation with renewable energy. However, NRR suffers from sluggish kinetics owing to difficult N2 adsorption and N≡N cleavage. Now, nanoporous palladium hydride is reported as electrocatalyst for electrochemical N2 reduction under ambient conditions, achieving a high ammonia yield rate of 20.4 μg h−1 mg−1 with a Faradaic efficiency of 43.6 % at low overpotential of 150 mV. Isotopic hydrogen labeling studies suggest the involvement of lattice hydrogen atoms in the hydride as active hydrogen source. In situ Raman analysis and density functional theory (DFT) calculations further reveal the reduction of energy barrier for the rate‐limiting *N2H formation step. The unique protonation mode of palladium hydride would provide a new insight on designing efficient and robust electrocatalysts for nitrogen fixation.

Deep Eutectic Solvents for Boosting Electrochemical Energy Storage and Conversion: A Review and Perspective

“…Although the synthesis of NH 3 from N 2 and H 2 is exothermic under standard conditions, NRR is kinetically sluggish and contains complex multistep owing to difficult N 2 adsorption and NN cleavage. [170,171] Designing novel electrocatalysts by lowering the N 2 reduction energy has been explored to surmount the energy barriers. Recently, DES (PEG 200/ thiourea)-derived Fe 3 S 4 nanosheets were solvothermally prepared to use as an NRR electrocatalyst.…”

Exploration and Investigation of Periodic Elements for Electrocatalytic Nitrogen Reduction

“…43.60% efficiency with 20.40 µg h −1 mg cat −1 was achieved. [205] In situ studies and DFT calculations revealed that unique NRR reaction mechanism which differs in protonation step played vital role in improving the efficiency.…”

An Overview on Noble Metal (Group VIII)‐based Heterogeneous Electrocatalysts for Nitrogen Reduction Reaction

“…Notably, Pt‐based catalysts of ECSA can be determined via the H adsorption‐desorption from CV curves [22] . Pd‐based catalysts of ECSA can be calculated by the reduction charge of PdO reduction peak from CV curves [21b] . Although each catalyst with different preparation method, catalyst loadings and morphology, will lead to different catalytic ability of NRR in the previous reports, the electrochemical results (the current densities, NH 3 yield rates) can be normalized to the ECSA to exclude the effects of different catalysts, allowing for a fair comparison.…”

“…As described above, ‐PdH formation during electrochemical process can improve the catalytic performance through a hydride migration mechanism. Based on this premise, nanoporous palladium hydride were prepared by a dealloying method and used as an excellent electro‐catalyst for NRR with the NH 3 formation rates of 20.4 mg h −1 mg cat −1 and FEs of 43.6% [21b] . They also used isotopic tracer methods to understand the mechanism of NRR on nanoporous‐PdH 0.43 .…”

“…c) In‐situ Raman spectra and d) relevant contour plots of np‐PdH 0.43 at different voltages. Copyright 2020 Wiley‐VCH [21b] . f) Rh (111), g) Rh 2 P (200) and h) RhP 2 (−111) of side view structures.…”