Accelerating H* Redistribution via Hydrogen Spillover for Enhanced Electrochemical Hydrogen Production From Formaldehyde.

Producing hydrogen from formaldehyde oxidation reaction (FOR) offers a promising low-energy approach for generating clean fuel. However, the FOR involves continuous C─H bond cleavage of adsorbed intermediates to generate abundant surface H*. This necessitates rapid transfer and consumption of H* to sustain fast oxidation kinetics. Herein, we developed a hydrogen-spillover strategy to redistribute these surface H* to accelerate FOR kinetics by constructing RhCu single-atom alloy supported on a Cu single-atom-rich carbon matrix (RhCu@CuSANC). In this design, Cu incorporation creates a favorable landscape for H* migration toward the CuSANC support, which acts as efficient H* acceptors and H─H coupling centers. Verified through multiple analyses, this hydrogen-spillover mechanism is demonstrated to enhance FOR activity by accelerating H* redistribution. Consequently, RhCu@CuSANC shows outstanding FOR performance, achieving a current density of 800 mA cm- 2 at 0.39 V with nearly 100% H2 selectivity and excellent durability. When integrated into a hybrid alkali-acid cell, it provides an open circuit voltage of 1.72 V and peak power density of 152.6 mW cm- 2 with stable H2 production for over 1200 h at 10 mA cm- 2. These results demonstrate that hydrogen spillover boosts oxidative electrocatalysis, providing a general design principle for multicomponent catalysts with coordinated hydrogen dynamics.