Partially Oxidized Pd/PdO/CC Catalyst for Hydrogen Production at Anodic and Cathodic in a Formaldehyde & Water Coelectrolysis System

Partial oxidation is a strategic method to optimize catalytic materials, particularly for multifunctional systems. Palladium (Pd), renowned for its dual activity in formaldehyde oxidation (FOR) and hydrogen evolution reactions (HER), is engineered here into a partially oxidized Pd/PdO catalyst. This design integrates metallic Pd's conductivity with PdO's oxidative properties, overcoming PdO's inherent limitations in adsorption and electron transfer. The Pd/PdO catalyst achieves a current density of 50 mA cm −2 at a low FOR potential of 0.63 V versus reversible hydrogen electrode, while HER performance remains robust even in formaldehyde‐containing electrolytes, maintaining unaltered onset potentials and kinetics. Hydrogen sources and mapped FOR‐driven hydrogen generation pathways through in situ differential electrochemical mass spectrometry and product analysis are conclusively identified. Density functional theory calculations demonstrate that Pd 0 –Pd 2+ interfacial synergy enhances formaldehyde adsorption, while partial density of states (PDOS) analyzes reveal electronic modulation induced by partial oxidation, rationalizing the improved activity. This work not only elucidates the bifunctional mechanism of Pd/PdO but also highlights its potential in formaldehyde–water coelectrolysis systems. By bridging material design with atomic‐level mechanistic insights, the study establishes a universal framework for developing efficient, oxidation‐engineered catalysts for sustainable hydrogen production.