Mechanism

The first electrode comprises a carbon framework whose sp² lattice sites are progressively converted to sp³ hybridization during charging through covalent attachment of hydrogen atoms. The charging operation is driven by electrolytic water-splitting at the electrode-electrolyte interface: water molecules in the adjacent electrolyte are reduced to produce nascent hydrogen, which is captured at carbon sites before it can recombine to form gaseous H₂. The result is a carbon-hydrogen bond population whose stoichiometry approaches CH at full saturation. This C-H bond formation is the load-bearing energy-storage event of the charged state, and its formation enthalpy supplies the round-trip free-energy budget recovered upon discharge.

Discharge proceeds by cooperative cleavage of adjacent C-H bonds across the lattice. Rather than each bond breaking independently, the local sp³-to-sp² rehybridization of one site lowers the activation energy at neighboring sites, permitting a cascade-like progression of cleavage events through the carbon network. The cascade releases hydrogen as proton-electron pairs that traverse the cell to re-form water at the second electrode, returning the carbon framework toward its planar sp² configuration. Because the lattice topology is preserved through both half-reactions, only the hybridization state of carbon sites and the population of bonded hydrogens change, the cycle admits repeated execution without progressive structural damage. The reversibility is mechanistic, not statistical; the same atomic positions are re-occupied across cycles.

The graphane-class designation refers to the family of fully or partially hydrogenated graphene derivatives in which carbon atoms occupy sp³ hybridized positions with hydrogen covalently bonded to one face or alternating faces of the lattice. The disclosed composition need not be perfectly periodic graphane; partial hydrogenation, stacking-disordered analogs, and hydrogenated few-layer graphenes all fall within the bond-class so long as the C-H bond is the dominant hydrogen-binding mode.

Operating Parameters

Hydrogen content ranges from approximately 1 to 8 weight percent in the charged state, with the upper bound corresponding to fully-saturated graphane (CH stoichiometry, ≈7.7 wt% H). Engineered cells typically operate within a 2 to 6 weight percent envelope to balance gravimetric capacity against cycling stability, operation closer to full saturation increases capacity but introduces lattice strain that may shorten cycle life, while operation well below 2 wt% wastes the available carbon mass. In the discharged state, residual hydrogen content is substantially reduced, typically below 0.5 wt%, and the carbon framework returns to a predominantly sp² configuration.

The hydrogen content range admits direct gravimetric comparison with established hydrogen-storage benchmarks. The U.S. Department of Energy gravimetric storage targets fall within the disclosed envelope, and the upper bound of full graphane saturation exceeds those targets by a meaningful margin. Translating gravimetric content into volumetric terms depends on the framework density of the carbon host, which varies between low-density turbostratic carbons (favoring high gravimetric figures) and dense few-layer graphenes (favoring high volumetric figures). The cell designer selects framework density to align gravimetric and volumetric capacity with the target application's mass-versus-volume budget.

Charging proceeds at electrode potentials sufficient to drive water reduction (cathodic potentials referenced to the cell's internal water-splitting equilibrium), with rate limited by the kinetics of nascent-hydrogen capture at carbon sites versus competing H₂ evolution. The cell operates at ambient temperature; no elevated thermal regime is required to populate or to discharge the C-H bond inventory, which is a deliberate departure from prior carbon-hydrogen-storage proposals that require high-temperature catalysis. Round-trip coulombic efficiency is governed by the fraction of nascent hydrogen captured covalently versus the fraction lost to H₂ evolution; cell architecture (electrode microstructure, electrolyte composition, current density) determines this fraction in practice.

Alternative Embodiments

The carbon framework admits multiple morphologies. Single-layer graphene, few-layer graphene, graphene nanoplatelets, reduced graphene oxide, and porous turbostratic carbons all present sp² carbon sites available for hydrogenation. The choice trades surface-area-to-mass ratio (favoring high-surface-area materials for fast kinetics) against framework integrity (favoring well-ordered lattices for cycling stability). Composite electrodes combining graphene-class material with conductive additives and polymeric binders are within scope provided the C-H bond remains the dominant hydrogen-binding mode.

Doped or substitutionally-modified carbon frameworks (nitrogen-doped, boron-doped, defect-engineered) are also within scope. These modifications alter local electronic structure at carbon sites and can shift C-H bond formation enthalpy, providing a tuning parameter for the cell's open-circuit voltage and round-trip efficiency. Functionalized graphene carrying oxygen or hydroxyl groups in the discharged state likewise falls within the disclosure when the principal cycling mechanism is C-H formation and cleavage.

Composition

The charged-state composition is graphane-class: an sp³ carbon framework with hydrogen atoms covalently bonded to carbon sites. This composition is structurally and chemically distinct from three classes of prior hydrogen-storage materials. Physisorbed hydrogen, H₂ molecules held at carbon surfaces by van der Waals forces, would not survive ambient temperature without cryogenic confinement and represents a distinct binding mode. Metal hydrides (e.g., LaNi₅H₆, MgH₂, NaAlH₄) store hydrogen via metal-H bonds in which the metal acts as the binding partner; the disclosed composition contains no metal hydride phase. Intercalated hydrogen, interstitial occupancy of layered host lattices without covalent bond formation, is distinguished by the absence of localized bonding orbitals; the disclosed composition is defined by localized C-H bonding orbitals at each occupied site.

The discharged-state composition reverts toward planar sp² carbon, with residual C-H, C-OH, or C=O groups at edge or defect sites. The cell's electrolyte is aqueous or aqueous-organic mixed phase compatible with electrolytic water-splitting. The second electrode (counter electrode) hosts the complementary half-reaction and is separately disclosed.

Prior-Art Distinction

Conventional lithium-ion batteries store charge through lithium intercalation into graphite, in which lithium ions occupy interstitial sites between carbon layers without forming covalent C-Li bonds. The disclosed mechanism is structurally distinct: hydrogen forms localized covalent bonds at carbon sites, raising hybridization from sp² to sp³. Hydrogen-storage research on carbon nanotubes and metal-organic frameworks has historically relied on physisorption at cryogenic temperatures or on chemisorption requiring elevated temperatures and catalysts; the disclosed cell admits ambient-temperature electrolytic charging and discharging without external catalyst, with hydrogen flux supplied internally by water splitting at the electrode-electrolyte interface. Graphane synthesis has been demonstrated in laboratory settings via plasma hydrogenation of graphene; the disclosure differs by integrating graphane formation into a closed electrochemical cycle rather than treating it as an end-state material.

Disclosure Scope

The disclosure encompasses any electrochemical cell in which the first electrode comprises a carbon framework that reversibly hosts hydrogen as covalent C-H bonds at concentrations in the disclosed weight-percent range, where charging is driven by electrolytic water-splitting at the same electrode and discharge proceeds via cooperative C-H cleavage. The scope includes graphane and graphane-class compositions across morphologies (single-layer, few-layer, nanoplatelet, porous turbostratic), doped and substituted variants, and composite electrodes. The scope excludes hydrogen-storage modes whose principal binding is physisorption, metal-hydride coordination, or interstitial intercalation. The disclosure is recited in Provisional Application 64/052,368 and is intended to read on the carbon-bound-cell architecture as practiced under that filing.

Operationally, the disclosed primitive is intended to support cycling at gravimetric capacities competitive with established secondary battery chemistries while admitting the safety profile of a sealed aqueous cell. The covalent C-H bond inventory is non-flammable in the bound state, no free H₂ inventory is held within the cell at rest, and the cell's energy density is bounded by the bond chemistry rather than by the volumetric efficiency of any compressed or cryogenic phase. The cell's open-circuit voltage is set by the difference between the C-H bond formation enthalpy at the first electrode and the complementary oxygen-bound state enthalpy at the second electrode, with electrolyte composition supplying small adjustments through Nernstian shifts. Practical cell engineering must address competing kinetic pathways at the first electrode: hydrogen evolution as gaseous H₂, hydrogen recombination at framework defects, and slow C-H formation at low-current-density operation. Each pathway is mitigated by electrode microstructure design, current-density operating window, and electrolyte composition selected to favor the productive C-H formation channel.

The scope further extends to cells in which the first electrode is operated as part of a stack or array, with multiple graphane-class electrodes connected in series or parallel to scale voltage and capacity. Stack-level integration does not alter the unit-cell mechanism described herein. The scope also extends to cells incorporating the disclosed primitive within the cavity-bath architecture and the density-storage architecture also disclosed in the parent provisional, where the C-H bond formation primitive supplies the first-electrode chemistry of those architectures.